ALBERT

Description: The Central African forests, the planet's second largest rainforest block, are key to global environmental health. They influence climate change through their crucial role in carbon sinking and storage, affect weather patterns across Africa, and safeguard unique species and biodiverse communities. Their fate is important to everyone, not just today's inhabitants. The forests cover seven countries, and the differing socioeconomic histories and trajectories of these nations determine divergent fates for people, trees, and wildlife across the region. We review current knowledge of how the Central African forests have been shaped by climate and human activity within the region and assess how they may evolve under future climate change, population growth, and the Anthropocene race for wealth and energy. We highlight three different environmental trajectories for the countries of the region, identify key current regional issues that have an international dimension, and highlight five new points of future concern.

Description: Vegetation modifies land-surface properties, mediating the exchange of energy, moisture, trace gases, and aerosols between the land and the atmosphere. These exchanges influence the atmosphere on local, regional, and global scales. Through altering surface properties, vegetation change can impact on weather and climate. We review current understanding of the processes through which tropical land-cover change (LCC) affects rainfall. Tropical deforestation leads to reduced evapotranspiration, increasing surface temperatures by 1–3 K and causing boundary layer circulations, which in turn increase rainfall over some regions and reduce it elsewhere. On larger scales, deforestation leads to reductions in moisture recycling, reducing regional rainfall by up to 40%. Impacts of future tropical LCC on rainfall are uncertain but could be of similar magnitude to those caused by climate change. Climate and sustainable development policies need to account for the impacts of tropical LCC on local and regional rainfall.

Description: The ecosystem services (ES) framework was developed to articulate and measure the benefits humans receive from ecosystems. Cultural ecosystem services (CES), usually defined as the intangible and nonmaterial benefits ecosystems provide, have been relatively neglected by researchers and policy-makers compared to provisioning, supporting, and regulating services. Although valuing CES poses several conceptual and methodological difficulties, it is of huge interest and importance because of the linkages between cultural values, valuation methods, and the individual and collective decision-making that influence ecosystems and human wellbeing. This review is not a how-to guide, but rather examines key conceptual issues and maps critical areas of debate. There is a range of potential approaches to assessing CES; however, choices regarding valuation methods and their role in decision-making are shaped by cultural and political dynamics. CES are at a crossroads. They can potentially act as a fruitful conceptual container for a broad range of interdisciplinary research into human-environment relations and transform how decisions regarding the environment are made, but they can also be used to legitimize and entrench modes of decision-making that marginalize and undermine the very values they are intended to protect.

Description: Land-management options for greenhouse gas removal (GGR) include afforestation or reforestation (AR), wetland restoration, soil carbon sequestration (SCS), biochar, terrestrial enhanced weathering (TEW), and bioenergy with carbon capture and storage (BECCS). We assess the opportunities and risks associated with these options through the lens of their potential impacts on ecosystem services (Nature's Contributions to People; NCPs) and the United Nations Sustainable Development Goals (SDGs). We find that all land-based GGR options contribute positively to at least some NCPs and SDGs. Wetland restoration and SCS almost exclusively deliver positive impacts. A few GGR options, such as afforestation, BECCS, and biochar potentially impact negatively some NCPs and SDGs, particularly when implemented at scale, largely through competition for land. For those that present risks or are least understood, more research is required, and demonstration projects need to proceed with caution. For options that present low risks and provide cobenefits, implementation can proceed more rapidly following no-regrets principles.

Description: Sanitation research focuses primarily on containing human waste and preventing disease; thus, it has traditionally been dominated by the fields of environmental engineering and public health. Over the past 20 years, however, the field has grown broader in scope and deeper in complexity, spanning diverse disciplinary perspectives. In this article, we review the current literature in the range of disciplines engaged with sanitation research in low- and middle-income countries (LMICs). We find that perspectives on what sanitation is, and what sanitation policy should prioritize, vary widely. We show how these diverse perspectives augment the conventional sanitation service chain, a framework describing the flow of waste from capture to disposal. We review how these perspectives can inform progress toward equitable sanitation for all [i.e., Sustainable Development Goal (SDG) 6]. Our key message is that both material and nonmaterial flows—and both technological and social functions—make up a sanitation “system.” The components of the sanitation service chain are embedded within the flows of finance, decision making, and labor that make material flows of waste possible. The functions of capture, storage, transport, treatment, reuse, and disposal are interlinked with those of ensuring equity and affordability. We find that a multilayered understanding of sanitation, with contributions from multiple disciplines, is necessary to facilitate inclusive and robust research toward the goal of sanitation for all.

Description: Achieving a truly sustainable energy transition requires progress across multiple dimensions beyond climate change mitigation goals. This article reviews and synthesizes results from disparate strands of literature on the coeffects of mitigation to inform climate policy choices at different governance levels. The literature documents many potential cobenefits of mitigation for nonclimate objectives, such as human health and energy security, but little is known about their overall welfare implications. Integrated model studies highlight that climate policies as part of well-designed policy packages reduce the overall cost of achieving multiple sustainability objectives. The incommensurability and uncertainties around the quantification of coeffects become, however, increasingly pervasive the more the perspective shifts from sectoral and local to economy wide and global, the more objectives are analyzed, and the more the results are expressed in economic rather than nonmonetary terms. Different strings of evidence highlight the role and importance of energy demand reductions for realizing synergies across multiple sustainability objectives.

Description: The electric power sector around the world is undergoing long-term technical, economic, and market transformations. Part of these transformations is the challenge of integrating high shares of renewable energy, particularly variable wind and solar. The concept of flexibility of a power system is key in terms of balancing these variable sources while keeping the lights on. On the supply side, flexibility arises from innovations in flexible coal and gas power plants, energy storage, and renewables. On the demand side, many distributed resources—generation, flexible demand, storage, and electric vehicles—can also contribute, and likewise transmission and distribution networks, grid operations, and market designs. Experience with measures and innovations for grid integration in all these categories is given, from several jurisdictions like Germany, Denmark, and California, where renewables already provide 20–40% shares of electricity and plans to reach 50% exist. Questions point to areas of technology, economics, planning, operations, business, and policy that need further understanding and learning from experience.

Description: Biodiversity conservation interventions often aim to benefit both nature and people; however, the social impacts of these interventions remain poorly understood. We reviewed recent literature on the social impacts of four marine conservation interventions to understand the synergies, tradeoffs, and equity (STE) of these impacts, focusing on the direction, magnitude, and distribution of impacts across domains of human wellbeing and across spatial, temporal, and social scales. STE literature has increased dramatically since 2000, particularly for marine protected areas (MPAs), but remains limited. Few studies use rigorous counterfactual study designs, and significant research gaps remain regarding specific wellbeing domains (culture, education), social groups (gender, age, ethnic groups), and impacts over time. Practitioners and researchers should recognize the role of shifting property rights, power asymmetries, individual capabilities, and resource dependency in shaping STE in conservation outcomes, and utilize multi-consequential frameworks to support the wellbeing of vulnerable and marginalized groups.

Description: Transportation systems contribute significantly to air pollution and ∼15% globally and ∼25% in the United States to emissions climate-changing gases. In the United States, the Corporate Average Fuel Economy (CAFE) standards for motor vehicles were significantly raised in 2012 for the first time in almost three decades. The standards now call for an average across manufacturers of 54.5 miles per gallon (mpg) for new passenger cars by 2025, or 163 grams per mile (g/mi) of greenhouse gas (GHG) emissions, and of 47 mpg (196 g/mi) by 2021. The light truck standards, which include minivans and sport utility vehicles, call for fuel economy levels of 31 mpg (287 g/mi) in 2021 and of 40 mpg (222 g/mi) in 2025. Given approximately equal expected splits between car and light truck sales, these estimates imply combined car and light truck fleet averages of ∼40 to 41 mpg (217 to 222 g/mi) in 2021 and 50 mpg (178 g/mi) in 2025. However, because automakers have strategies to reduce GHGs in parallel with fuel economy, the actual in-use fuel economy of the fleet is expected to be somewhat lower. In this review, several automobile technology advances are described and assessed for providing relatively cost-effective solutions to meet CAFE standards for fuel economy and GHG reductions through 2025. The key points this review makes are that (a) loopholes in the current regulations will allow automakers to meet CAFE program goals with relatively minor incremental improvements to current technologies through 2025 and that (b) going beyond the current program, past 2025 to higher fuel economy levels and lower GHG emissions approaching 100 g/mi, is likely to involve heavier use of newer technologies especially including drivetrain electrification.

Description: We review the literature that investigates the relationship between foreign direct investment (FDI) and the environment. After reviewing the theoretical literature, we discuss two broad strands of research. First, the impact of environmental regulations on the choice of plant location and second, the impact of FDI on the emissions of various pollutants and the related question of whether we can observe environmental spillovers from foreign to domestic firms. Finally, we review the more recent literature on environmental outsourcing as an alternative to FDI and conclude with suggestions for future research.

Description: The extent to which natural capital can be substituted with manufactured or human capital in production is a key determinant of the possibility of long-run sustainable economic development. We review empirical literature pertaining to the degree of substitutability between natural capital and other forms of capital. We find that most available substitutability estimates do not stand up to careful scrutiny. Moreover, accurate substitutability estimates are even more difficult to produce for unpriced or mispriced resources. Finally, we provide evidence from industrial energy use, and agricultural land use, that suggests substitutability of natural capital with other forms of capital may be low to moderate.

Description: We compile global data to examine the current status, trends, threats, and opportunities in the world's wild-capture fisheries. We find that global fisheries have largely diverged—well-managed, often industrial fisheries tend to be in reasonably good health, while coastal fisheries, often from low-governance regions, tend to be in poor health. Good governance seems to play a central role, and we summarize key findings from the literature on how effective fishery management can simultaneously increase food security, livelihoods, and conservation outcomes. Other solutions, such as marine protected areas and big data, can be useful but will not, by themselves, solve the main fishery challenges. We conclude by examining notorious threats, such as climate change and lack of governance on the high seas, and find that these can be largely neutralized with good fishery management, suggesting that overall, the future of wild fisheries can be bright with effective fishery management interventions.

Description: Differentiating the impacts of climate change between 1.5°C and 2°C requires a regional and sector-specific perspective. Whereas for some regions and sectors the difference in climate variables might be indistinguishable from natural variability, other areas especially in the tropics and subtropics will experience significant shifts. In addition to region-specific changes in climatic conditions, vulnerability and exposure also differ substantially across the world. Even small differences in climate hazards can translate into sizeable impact differences for particularly vulnerable regions or sectors. Here, we review scientific evidence of regional differences in climate hazards at 1.5°C and 2°C and provide an assessment of selected hotspots of climate change, including small islands as well as rural, urban, and coastal areas in sub-Saharan Africa and South Asia, that are particularly affected by the additional 0.5°C global mean temperature increase. We interlink these with a review of the vulnerability and exposure literature related to these hotspots to provide an integrated perspective on the differences in climate impacts between 1.5°C and 2°C.

Description: I review the shocking current status of terrestrial mammals and then describe an approach to solving it, embracing a continuum of spatial and intellectual scales, from groundedness to geopolitics. Starting with an illustrative arena, the interface between agriculture and wildlife, I then outline the litany of threats to mammals and some successful approaches to their conservation, and document some broad-scale patterns regarding ecosystems, the mammalian communities within, and some implications for conservation. Observing that the battle for mammalian conservation is being badly lost, I dedicate the third part of this article to a combination of top-down and bottom-up, interdisciplinary studies, aspiring to a holistic approach that sets conservation in the wider sphere of the human enterprise and that I term transdisciplinary conservation.

Description: This review focuses on transnational governance in the minerals and mining sector. Although several initiatives have emerged to address specific governance challenges in this sector, knowledge of these efforts is piecemeal and little is known about patterns in transnational governance development across this issue area. We address these gaps by reviewing the extant research literature and analyzing empirical examples of transnational minerals and mining governance, using the gold sector as an illustrative case. We identify the social, humanitarian, security, and environmental problems manifest along the mineral lifecycle and consider the extent to which existing transnational governance initiatives address these issues. We call for future scholarship that addresses the diversity of transnational governance practices in the minerals and mining sector and explains emergent patterns in the particular forms of governance that dominate this issue area, as well the types of problems that have (and have not) received attention.

Description: Understanding the cultural dimensions of climate change requires understanding its religious aspects. Insofar as climate change is entangled with humans, it is also entangled with all the ways in which religion attends human ways of being. Scholarship on the connections between religion and climate change includes social science research into how religious identity figures in attitudes toward climate change, confessional and constructive engagements of religious thought with climate change from various communities and traditions, historical and anthropological analyses of how climate affects religion and religion interprets climate, and theories by which climate change may itself be interpreted as a religious event. Responses to climate change by indigenous peoples challenge the categories of religion and of climate change in ways that illuminate reflexive stresses between the two cultural concepts.

Description: Through integrative assessment, experts evaluate the state of knowledge on complex problems relevant to societies. In this review, we take stock of recent advances and challenges, rooting our analysis in climate change assessment. In particular, we consider four priorities in assessment: (a) integrating diverse evidence including quantitative and qualitative results and understanding, (b) applying rigorous expert judgment to evidence and its uncertainties, (c) exploring widely ranging futures and their connections to ongoing choices and actions, and (d) incorporating interactions among experts and decision makers in assessment processes. Across these assessment priorities, we survey past experiences, current practices, and possibilities for future experimentation, innovation, and learning. In our current era of climate and broader global change, integrative assessment can bolster decisions about contested and uncertain futures. We consider both opportunities and pitfalls in synthesizing and encompassing evidence and perspectives. Our aim is to advance transparent assessment for a sustainable future.

Description: This review explores what past environmental change in Africa—and African people's response to it—can teach us about how to cope with life in the Anthropocene. Organized around four drivers of change—climate; agriculture and pastoralism; megafauna; and imperialism, colonialism, and capitalism (ICC)—our review zooms in on key regions and debates, including desertification; rangeland degradation; megafauna loss; and land grabbing. Multiscale climate change is a recurring theme in the continent's history, interacting with increasingly intense human activities from several million years onward, leading to oscillating, contingent environmental changes and societally adaptive responses. With high levels of poverty, fast population growth, and potentially dramatic impacts expected from future climate change, Africa is emblematic of the kinds of social and ecological precariousness many fear will characterize the future globally. African people's innovation and adaptation to contingency may place them among the avant-garde with respect to thinking about Anthropocene conditions, strategies, and possibilities.

Description: The Anthropocene, the concept that the Earth has moved into a novel geological epoch characterized by human domination of the planetary system, is an increasingly prevalent framework for debate both in academia and as a wider cultural and policy zeitgeist. This article reviews the proliferation of literature surrounding this concept. It explores the origins and history of the concept, as well as the arguments surrounding its geological formalization and starting date ranging from the Pleistocene to the twentieth century. It examines perspectives and critiques of the concept from the Earth system sciences, ecological and geological sciences, and social sciences and humanities, exploring its role as a cultural zeitgeist and ideological provocation. I conclude by offering a personal perspective on the concept of the Anthropocene and its utility.

Description: The Intergovernmental Panel on Climate Change (IPCC) conducts policy-relevant but not policy-prescriptive assessments of climate science. In this review, we engage with some of the key design features, achievements, and challenges that situate and characterize the IPCC as an intergovernmental organization that is tasked with producing global environmental assessments (GEAs). These include the process of working through consensus to assess and summarize climate science and the need to include knowledge from as many of the 195 IPCC nation-states as possible, despite the structural inequalities between developed and developing countries. To highlight salient features that are unique to the IPCC but that offer lessons for other organizations that conduct GEAs, we include case studies on the politics of climate denialism, the use of geoengineering in mitigation scenarios, and the links between adaptive capacity, adaptation, and global development. We conclude with a discussion of institutional reflexivity. We consider how the IPCC can model an ethical and participatory response to climate change by critically examining, and being transparent about, the relation between science and politics.

Description: Corporate environmentalism (CE) pertains to firm-level efforts to reduce pollution and resource use along with protecting natural habitats. Importantly, firms pledge to undertake these actions beyond the requirements of the law. Although historically CE efforts focused on resource conservation, their contemporary focus is on pollution reduction to reduce direct harm to humans and their communities and on the protection of environmental sinks. We review two broad categories of CE: direct CE and indirect CE. Direct CE, whether undertaken unilaterally or collectively, pertains to firms themselves adopting policies that reduce the environmental impact of their activities, or disclosing information about their environmental performance. Indirect CE refers to policies of actors (such as financial institutions) that encourage firms seeking their resources (through loans, venture capital, etc.) to commit to environmental stewardship policies. Three key lessons emerge. First, firm-level characteristics, particularly size and economic performance, encourage CE. Second, although pressure from external stakeholders, especially environmental nongovernmental organizations (NGOs), has played an important role in discouraging policies that harm the environment, its effect on encouraging proenvironmental activities remains unclear. Third, the literature is ripe with serious methodological issues. The endogeneity between firms’ economic and environmental record and their CE efforts poses difficulty in drawing causal inferences.

Description: India is a significant player in climate policy and politics. It has been vocal in international climate negotiations, but its role in these negotiations has changed over time. In an interactive relationship between domestic policy and international positions, India has increasingly become a testing ground for policies that internalize climate considerations into development. This article critically reviews the arc of climate policy and politics in India over time. It begins by examining changes in knowledge and ideas around climate change in India, particularly in the areas of ethics, climate impacts, India's energy transition, linkages with sustainability, and sequestration. The next section examines changes in politics, policy, and governance at both international and national scales. The article argues that shifts in ideas and knowledge of impacts, costs, and benefits of climate action and shifts in the global context are reflected and refracted through discourses in India's domestic and international policies.

Description: Co-production has become a cornerstone of research within the sustainability sciences, motivating collaborations of diverse actors to conduct research in the service of societal and policy change. This review examines theoretical and empirical literature from sustainability science, public administration, and science and technology studies (STS) with the intention of advancing the theory and practice of co-production within sustainability science. We argue that co-production must go beyond stakeholder engagement by scientists to the more deliberate design of societal transitions. Co-production can contribute to such transitions by shifting the institutional arrangements that govern relationships between knowledge and power, science and society, and state and citizens. We highlight critical weaknesses in conceptualizations of co-production within sustainability sciences with respect to power, politics, and governance. We offer suggestions for how this can be rectified through deeper engagement with public administration and STS to offer a broad vision for enhancing the use, design, and practice of a more reflexive co-production in sustainability science.

Description: Ecotourism originated in the 1980s, at the dawn of sustainable development, as a way to channel tourism revenues into conservation and development. Despite the “win-win” idea, scholars and practitioners debate the meaning and merits of ecotourism. We conducted a review of 30 years of ecotourism research, looking for empirical evidence of successes and failures. We found the following trends: Ecotourism is often conflated with outdoor recreation and other forms of conventional tourism; impact studies tend to focus on either ecological or social impacts, but rarely both; and research tends to lack time series data, precluding authors from discerning effects over time, either on conservation, levels of biodiversity, ecosystem integrity, local governance, or other indicators. Given increasing pressures on wild lands and wildlife, we see a need to add rigor to analyses of ecotourism. We provide suggestions for future research and offer a framework for study design and issues of measurement and scaling.

Description: Consumption, although often considered an individual choice, is deeply ingrained in behaviors, cultures, and institutions, and is driven and supported by corporate and government practices. Consumption is also at the heart of many of our most critical ecological, health, and social problems. What is referred to broadly as sustainable consumption has primarily focused on making consumption more efficient and gradually decoupling it from energy and resource use. We argue for the need to focus sustainable consumption initiatives on the key impact areas of consumption—transport, housing, energy use, and food—and at deeper levels of system change. To meet the scale of the sustainability challenges we face, interventions and policies must move from relative decoupling via technological improvements, to strategies to change the behavior of individual consumers, to broader initiatives to change systems of production and consumption. We seek to connect these emerging literatures on behavior change, structural interventions, and sustainability transitions to arrive at integrated frameworks for learning, iteration, and scaling of sustainability innovations. We sketch the outlines of research and practice that offer potentials for system changes for truly sustainable consumption.

Description: We review the major conceptual models of atmospheric moisture transport, which describe the link between evaporation from the ocean and precipitation over the continents. We begin by summarizing some of the basic aspects of the structure and geographical distribution of the two major mechanisms of atmospheric moisture transport, namely low-level jets (LLJs) and atmospheric rivers (ARs). We then focus on a regional analysis of the role of these mechanisms in extreme precipitation events with particular attention to the intensification (or reduction) of moisture transport and the outcome, in terms of precipitation anomalies and subsequent flooding (drought), and consider changes in the position and occurrence of LLJs and ARs with respect to any associated flooding or drought. We then conclude with a graphical summary of the impacts of precipitation extremes, highlighting the usefulness of this information to hydrologists and policymakers, and describe some future research challenges including the effects of possible changes to ARs and LLJs within the context of future warmer climates.

Description: The extraction of unconventional oil and gas—from shale rocks, tight sand, and coalbed formations—is shifting the geographies of fossil fuel production, with complex consequences. Following Jackson et al.’s ( 1 ) natural science survey of the environmental consequences of hydraulic fracturing, this review examines social science literature on unconventional energy. After an overview of the rise of unconventional energy, the review examines energy economics and geopolitics, community mobilization, and state and private regulatory responses. Unconventional energy requires different frames of analysis than conventional energy because of three characteristics: increased drilling density, low-carbon and “clean” energy narratives of natural gas, and distinct ownership and royalty structures. This review points to the need for an interdisciplinary approach to analyzing the resulting dynamic, multilevel web of relationships that implicates land, water, food, and climate. Furthermore, the review highlights how scholarship on unconventional energy informs the broader energy landscape and contested energy futures.

Description: The Anthropocene is characterized by a widespread biodiversity crisis that is rivaling prehistoric mass extinctions. Amphibians are the most threatened class of vertebrates. In addition to traditional threats such as land-use conversion and pollution, climate change and introduced diseases are expected to further reduce amphibian biodiversity. The fungal disease chytridiomycosis has caused the rapid extirpation of tens to possibly hundreds of amphibian species. Recent advances have revealed a deep evolutionary history and considerable variation in the virulence of strains of the fungal pathogen, patterns that need to be reconciled with the rapid spread of disease and demise of host populations. A conservation priority is surveillance of a newly discovered species of chytrid fungus that is killing European salamanders. The accelerated discovery of new amphibian species challenges existing conservation resources, but it is an opportunity to fill geographical gaps and to enhance programs aimed at preserving amphibian biodiversity.

Description: This article presents a critical assessment of the literature on sustainable consumption in the global North and South, in the context of accelerated and megascale transitions that are needed across all human activities, in ways that “leave no one behind,” as envisaged in the United Nations Sustainable Development Goals (SDGs). It challenges two dominant, related research foci: an emphasis on the individual and individual aspirations of the good life, and the policy incrementalism of rational, ecological modernization. Although conceding individuals must act consciously to advance sustainability, nuanced interpretations of collective sustainable living rarely feature in mainstream research. Discussion highlights values of extended family, tribe and community solidarity, and human and nonhuman interrelationships for harmonious, peaceful, spiritual, and material coexistence. Concepts such as Ahimsa (India), Buen Vivir (South America), Ubuntu (Africa), Hauora (New Zealand), or Shiawase and Ikigai (Japan), for example, can enrich understandings of sustainable living as long-term collective action for sustainable development and reducing climate change.

Description: Inclusive wealth is a measure designed to address whether society is on a sustainable development trajectory. Inclusive wealth is defined as the aggregate value of all capital assets. Increases in inclusive wealth indicate an improved productive base capable of supporting a higher standard of living in the future. To be truly inclusive, measures of inclusive wealth must include the value of all forms of capital that contribute to human well-being: human capital, manufactured capital, natural capital, and social capital. Sustainability concerns have increased attention on the ways of measuring the value of natural capital. We review various attempts to measure natural capital and to incorporate these into inclusive wealth including estimates using national wealth accounts and integrated ecological and economic models used to estimate ecosystem services. Empirically measuring the value of various types of capital in terms of a common metric is hugely challenging, and no current attempt to date can be said to be fully inclusive. Despite the empirical challenges, inclusive wealth provides a clear, coherent, and systematic framework for addressing sustainable development. Combining measures of semi-inclusive wealth that capture forms of capital that can be relatively easily measured in monetary terms with a set of biophysical metrics capturing important aspects of natural capital that are difficult to measure in monetary terms may provide a good set of signals of whether society is proceeding along a sustainable development trajectory.

Description: Global atmospheric methane concentrations have continued to rise in recent years, having already more than doubled since the Industrial Revolution. Further environmental change, especially climate change, in the twenty-first century has the potential to radically alter global methane fluxes. Importantly, changes in temperature, precipitation, and net primary production may induce positive climate feedback effects in dominant natural methane sources such as wetlands, soils, and aquatic ecosystems. Anthropogenic methane sources may also be impacted, with a risk of enhanced emissions from the energy, agriculture, and waste sectors. Here, we review the global sources of methane, the trends in fluxes by source and sector, and their possible evolution in response to future environmental change. We discuss ongoing uncertainties in flux estimation and projection, and highlight the great potential for multisector methane mitigation as part of wider global climate change policy.

Description: Antarctica and the Southern Ocean comprise a critical part of the Earth System. Their environments are better understood than ever before, yet the region remains poorly considered among international agreements to improve the state of the global environment. In part the situation owes to isolated regional regulation within the Antarctic Treaty System, and in part to the dated notion that Antarctica and the Southern Ocean are well conserved and relatively free from human impact. Here we review growth in knowledge of Antarctic environments and anthropogenic pressures on them. We show that the region's unusual diversity is facing substantial local and globally mediated anthropogenic pressure, on a par with environments globally. Antarctic environmental management and regulation is being challenged to keep pace with the change. Much benefit can be derived from consideration of Antarctic environmental and resource management in the context of global agreements.

Description: Biodiversity on marine islands is characterized by unique biogeographic, phylogenetic and functional characteristics. Islands hold a disproportionate amount of the world's biodiversity, and they have also experienced a disproportionate loss of it. Following human contact, island biodiversity has sustained negative human impacts increasing in rate and magnitude as islands transitioned from primary through secondary to tertiary economies. On islands, habitat transformation and invasive non-native species have historically been the major threats to biodiversity, and although these threats will continue in new forms, new impacts such as human-induced climate change and sea-level rise are emerging. Island biodiversity is changing with some species going extinct, others changing in abundance, non-native species becoming a part of many ecosystems, and humans shaping many ecological processes. Islands thus are microcosms for the emerging biodiversity and socioecological landscapes of the Anthropocene. Islands will require new strategies for the protection and restoration of their biodiversity, including maintaining biological and cultural heritage through regenerative practices, mainstreaming biodiversity in cultural and production landscapes, and engaging with the reality of novel ecosystems.

Description: This article discusses the conservation challenges of volant migratory transborder species and conservation governance primarily in North America. Many migratory species provide ecosystem service benefits to society. For example, insectivorous bats prey on crop pests and reduce the need for pesticides; birds and insects pollinate food plants; and birds afford recreational opportunities to hunters and birdwatchers. Migration is driven by the seasonal availability of resources; as resources in one area become seasonally scarce, individuals move to locations where resources have become seasonally abundant. The separation of the annual lifecycle means that species management and governance is often fractured across international borders. Because migratory species depend on habitat in different locations, their ability to provide ecosystem services in one area depends on the spatial subsidies, or support, provided by habitat and ecological processes in other areas. This creates telecouplings, or interconnections across geographic space, of areas such that impacts to the habitat of a migratory species in one location will affect the benefits enjoyed by people in other locations. Information about telecoupling and spatial subsidies can be used to craft new governance arrangements such as Payment for Ecosystem Services programs that target specific stakeholder groups and locations. We illustrate these challenges and opportunities with three North American case studies: the Duck Stamp Program, Mexican free-tailed bats (Tadarida brasiliensis mexicana), and monarch butterflies (Danaus plexippus).

Description: Rare earths, sometimes called the vitamins of modern materials, captured public attention when their prices increased more than tenfold in 2010 and 2011. As prices fell between 2011 and 2016, rare earths receded from public view, but less visibly, they became a major focus of innovative activity in companies, government laboratories, and universities. Geoscientists worked to better understand the resource base and improve our knowledge about mineral deposits that can be mines in the future. Process engineers carried out research that is making primary production and recycling more efficient. Materials scientists and engineers searched for substitutes that require fewer or no rare earths while providing properties comparable or superior to those of existing materials. As a result, even though global supply chains are not significantly different now than they were before the market disruption, the innovative activity motivated by the disruption will likely have far-reaching, if unpredictable, consequences for supply chains of rare earths in the future.

Description: After several years of REDD+ (reducing emissions from deforestation and forest degradation in developing countries, and the role of conservation, sustainable management of forests, and enhancement of forest carbon stocks in developing countries) readiness, countries are starting to move toward REDD+ implementation and accessing results-based payments (RBPs). Currently various parallel processes for accessing RBPs exist, including project and jurisdictional—approaches that often operate under a nascent national framework. This review is structured around the key considerations for countries to implement REDD+ and access RBPs. It offers a discussion focusing on three areas that are crucial for the success of REDD+: ( a) REDD+ in the context of Nationally Determined Contributions (NDCs) under the Paris Agreement and the UN Sustainable Development Goals (SDGs), ( b) the role of the private sector in achieving emissions reductions, and ( c) access to RBPs for REDD+. We present some key considerations for future issues and possible successes of REDD+ implementation.

Description: We review future global demand for electricity and major technologies positioned to supply it with minimal greenhouse gas (GHG) emissions: renewables (wind, solar, water, geothermal, and biomass), nuclear fission, and fossil power with CO2 capture and sequestration. We discuss two breakthrough technologies (space solar power and nuclear fusion) as exciting but uncertain additional options for low-net GHG emissions (i.e., low-carbon) electricity generation. In addition, we discuss grid integration technologies (monitoring and forecasting of transmission and distribution systems, demand-side load management, energy storage, and load balancing with low-carbon fuel substitutes). For each topic, recent historical trends and future prospects are reviewed, along with technical challenges, costs, and other issues as appropriate. Although no technology represents an ideal solution, their strengths can be enhanced by deployment in combination, along with grid integration that forms a critical set of enabling technologies to assure a reliable and robust future low-carbon electricity system.

Description: Urban heat island (UHI) manifests as the temperature rise in built-up urban areas relative to the surrounding rural countryside, largely because of the relatively greater proportion of incident solar energy that is absorbed and stored by man-made materials. The direct impact of UHI can be significant on both daytime and night-time temperatures, and the indirect impacts include increased air conditioning loads, deteriorated air and water quality, reduced pavement lifetimes, and exacerbated heat waves. Modifying the thermal properties and emissivity of roofs and paved surfaces and increasing the vegetated area within the city are potential mitigation strategies. A quantitative comparison of their efficacies and costs suggests that so-called cool roofs are likely the most cost-effective UHI mitigation strategy. However, additional research is needed on how to modify surface emissivities and dynamically control surface and material properties, as well as on the health and socioeconomic impacts of UHI.

Description: Here, we identify the extant species of marine megafauna (〉45 kg maximum reported mass), provide a conceptual template for the ways in which these species influence the structure and function of ocean ecosystems, and review the published evidence for such influences. Ecological influences of more than 90% of the 338 known species of extant ocean megafauna are unstudied and thus unknown. The most widely known effect of those few species that have been studied is direct prey limitation, which occurs through consumption and risk avoidance behavior. Consumer-prey interactions result in indirect effects that extend through marine ecosystems to other species and ecological processes. Marine megafauna transport energy, nutrients, and other materials vertically and horizontally through the oceans, often over long distances. The functional relationships between these various ecological impacts and megafauna population densities, in the few well-studied cases, are characterized by phase shifts and hysteresis.

Description: Hundreds of millions of the world's poorest people directly depend on smallholder farming systems. These people now face a changing climate and associated societal responses. We use mapping and a literature review to juxtapose the climate fate of smallholder systems with that of other agricultural systems and population groups. Limited direct evidence contrasts climate impact risk in smallholder agricultural systems versus other farming systems, but proxy evidence suggests high smallholder vulnerability. Smallholders distinctively adapt to climate shocks and stressors. Their future adaptive capacity is uncertain and conditional upon the severity of climate change and socioeconomic changes from regional development. Smallholders present a greenhouse gas (GHG) mitigation paradox. They emit a small amount of CO2 per capita and are poor, making GHG regulation unwarranted. But they produce GHG-intensive food and emit disproportionate quantities of black carbon through traditional biomass energy. Effectively accounting for smallholders in mitigation and adaption policies is critical and will require innovative solutions to the transaction costs that enrolling smallholders often imposes. Together, our findings show smallholder farming systems to be a critical fulcrum between climate change and sustainable development.

Description: Approximately 40% of the global population relies on traditional bioenergy, accounting for 9% of global energy use and 55% of global wood harvest. However, knowledge about the environmental impacts of traditional bioenergy is fragmented. This review addresses several persistent questions and summarizes recent research on land cover change (LCC) and pollution emissions resulting from traditional bioenergy use. We also review recent studies analyzing transitions from traditional bioenergy to cleaner stoves and fuels. Between 27 and 34% of the wood fuel harvest in 2009 was unsustainable, with large geographical variations. Almost 300 million rural people live in wood fuel “hotspots,” concentrated in South Asia and East Africa, creating risks of wood-fuel-driven degradation. Different fuels and stoves show variation in climate-forcing emissions. Many, but not all, nontraditional stoves result in lower emissions than traditional models. Traditional bioenergy makes substantial contributions to anthropogenic black carbon (BC) emissions (18–30%) and small contributions to total anthropogenic climate impacts (2–8%). Transitions from traditional fuels and devices have proven difficult. Stacking, i.e., the use of multiple devices and fuels to satisfy household energy needs, is common, showing the need to shift stove interventions from the common approach that promotes one fuel and one device to integrated approaches that incorporate deep understanding of local needs and practices, and multiple fuels and devices, while monitoring residual use of traditional technologies.

Description: Scholars and activists mobilize increasingly the term degrowth when producing knowledge critical of the ideology and costs of growth-based development. Degrowth signals a radical political and economic reorganization leading to reduced resource and energy use. The degrowth hypothesis posits that such a trajectory of social transformation is necessary, desirable, and possible; the conditions of its realization require additional study. Research on degrowth has reinvigorated the limits to growth debate with critical examination of the historical, cultural, social, and political forces that have made economic growth a dominant objective. Here we review studies of economic stability in the absence of growth and of societies that have managed well without growth. We reflect on forms of technology and democracy com-patible with degrowth and discuss plausible openings for a degrowth transition. This dynamic and productive research agenda asks inconvenient questions that sustainability sciences can no longer afford to ignore.

Description: The livestock and environment nexus has been the subject of considerable research in the past decade. With a more prosperous and urbanized population projected to grow significantly in the coming decades comes a gargantuan appetite for livestock products. There is growing concern about how to accommodate this increase in demand with a low environmental footprint and without eroding the economic, social, and cultural benefits that livestock provide. Most of the effort has focused on sustainably intensifying livestock systems. Two things have characterized the research on livestock and the environment in the past decade: the development of increasingly disaggregated and sophisticated methods for assessing different types of environmental impacts (climate, water, nutrient cycles, biodiversity, land degradation, deforestation, etc.) and a focus on examining the technical potential of many options for reducing the environmental footprint of livestock systems. However, the economic or sociocultural feasibility of these options is seldom considered. Now is the time to move this agenda from knowledge to action, toward realizable goals. This will require a better understanding of incentives and constraints for farmers to adopt new practices and the design of novel policies to support transformative changes in the livestock sector. It will also require novel forms of engagement, interaction, and consensus building among stakeholders with enormously diverse objectives. Additionally, we have come to realize that managing the demand trajectories of livestock products must be part of the solution space, and this is an increasingly important research area for simultaneously achieving positive health and environmental outcomes.

Description: Carbon emissions in an industrialized world have created two problems for coral reefs: climate change and ocean acidification. Climate change drives ocean warming, which impacts biological and ecological reef processes, triggers large-scale coral bleaching events, and fuels tropical storms. Ocean acidification slows reef growth, alters competitive interactions, and impairs population replenishment. For managers and policymakers, ocean warming and acidification represent an almost paradoxical challenge by eroding reef resilience and simultaneously increasing the demand for reef resilience. Here, I address this problem in the context of challenges and potential solutions. Management efforts can compensate for reduced coral reef resilience in the face of global change, but to a limited extent and over a limited time frame. Critically, a realistic perspective on what sustainability measures can be achieved for coral reefs in the face of ocean warming and acidification is important to avoid setting unachievable goals for regional and local-scale management programs.

Description: Climate action has two pillars: mitigation and adaptation. Mitigation faces collective action issues because its costs are focused on specific locations/actors but benefits are global and nonexcludable. Adaptation, in contrast, creates local benefits, and therefore should face fewer collective action issues. However, governance units vary in the types of adaptation policies they adopt. To explain this variation, we suggest conceptualizing adaptation-as-politics because adaptation speaks to the issues of power, conflicting policy preferences, resource allocation, and administrative tensions. In examining who develops and implements adaptation, we explore whether adaptation is the old wine of disaster management in the new bottle of climate policy, and the tensions between national and local policy making. In exploring what adaptation policies are adopted, we discuss maladaptation and the distinction between hard and soft infrastructure. Finally, we examine why politicians favor visible, hard adaptation over soft adaptation, and how international influences shape local policy.

Description: Landscape approaches have become en vogue in the past couple of decades. Originating from nineteenth-century landscape geography, this renewed popularity since the 1980s is fueled by debates on—among others—nature conservation, landscape restoration, ecosystem services, competing claims on land and resources, sectorial land-use policies, sustainable development, and sense of place. This review illuminates the ambition and potential of these landscape approaches for interdisciplinary and cross-sectoral collaboration. To show this, we work with a T-shaped interdisciplinary model. After a short history of the landscape approaches, we dive into their key dimensions—from ecology to economics and culture to politics. Thereafter, we bring these dimensions together again and reflect on the integrative potential of landscape approaches for offering common ground to various disciplines and sectors. Two examples of applications are also dealt with: a landscape governance framework and a landscape capability framework.

Description: Losses from natural hazards, including geophysical and hydrometeorological hazards, have been increasing worldwide. This review focuses on the process by which scientific evidence about natural hazards is applied to support decision making. Decision analysis typically involves estimating the probability of extreme events; assessing the potential impacts of those events from a variety of perspectives; and evaluating options to plan for, mitigate, or react to events. We consider issues that affect decisions made across a range of natural hazards, summarize decision methodologies, and provide examples of applications of decision analysis to the management of natural hazards. We conclude that there is potential for further exchange of ideas and experience between natural hazard research communities on decision analysis approaches. Broader application of decision methodologies to natural hazard management and evaluation of existing decision approaches can potentially lead to more efficient allocation of scarce resources and more efficient risk management.

Description: As populations become more affluent and urbanized, diets are shifting such that they are becoming higher in calories and include more highly processed foods and animal products. These dietary shifts are driving increases in diet-related diseases and are also causing environmental degradation. These linked impacts pose a new key issue for global society—a diet, health, and environment trilemma. Recent dietary shifts have contributed to increasing diet-related health and environmental impacts, including an 80% increase in global diabetes prevalence and an 860% increase in global nitrogen fertilizer use. Furthermore, if current dietary trajectories were to continue for the next several decades, diet-related diseases would account for three-quarters of the global burden of disease and would also lead to large increases in diet-related environmental impacts. We discuss how shifts to healthier diets—such as some Mediterranean, pescetarian, vegetarian, and vegan diets—could reduce incidence of diet-related diseases and improve environmental outcomes. In addition, we detail how other interventions to food systems that use known technologies and management techniques would improve environmental outcomes.

Description: Solar geoengineering research in the social sciences and humanities has largely evolved in parallel with research in the natural sciences. In this article, we review the current state of the literature on the ethical, legal, economic, and social science aspects of this emerging area. We discuss issues regarding the framing and futures of solar geoengineering, empirical social science on public views and public engagement, the evolution of ethical concerns regarding research and deployment, and the current legal and economic frameworks and emerging proposals for the regulation and governance of solar geoengineering.

Description: Social-ecological systems (SES) research offers new theory and evidence to transform sustainable development to better contend with the challenges of the Anthropocene. Four insights from contemporary SES literature on ( a) intertwined SES, ( b) cross-scale dynamics, ( c) systemic tipping points, and ( d) transformational change are explored. Based on these insights, shifts in sustainable development practice are suggested to recognize and govern the complex and codeveloping social and ecological aspects of development challenges. The potential susceptibility of SES to nonlinear systemic reconfigurations is highlighted, as well as the opportunities, agency, and capacities required to foster reconfigurative transformations for sustainable development. SES research proposes the need for diverse values and beliefs that are more in tune with the deep, dynamic connections between social and ecological systems to transform development practice and to support capacities to deal with shocks and surprises. From these perspectives, SES research offers new outlooks, practices, and novel opportunity spaces from which to address the challenges of the Anthropocene.

Description: Soils represent a significant reservoir of biological diversity that underpins a broad range of key processes and moderate ecosystem service provision. Our understanding of the role that soil organisms play in ecosystems is still developing, but the increased investigation into biodiversity-ecosystem functioning relationships in soils over the past couple of decades has provided insights that have greatly enhanced our ability to sustainably manage soil biodiversity. In this review, we synthesize emerging knowledge of soil biodiversity as a natural resource that supports the functioning of terrestrial ecosystems and their delivery of ecosystem services. We explore how environmental changes alter soil biodiversity and how this in turn can affect ecosystem processes as well as resistance and resilience to environmental changes. We then discuss ways to include soil biodiversity in management strategies for sustainable production and biodiversity conservation. We conclude by highlighting key research challenges to further improve our knowledge of soil biodiversity and its management.

Description: China has emerged as a global economic powerhouse after four decades of unprecedented growth. Such growth has generated many environmental challenges with enormous ecological, socioeconomic, and health consequences in China and beyond. Although the overall quality of air and water is starting to improve, both are still below national and international standards. Water shortages are widespread. Biodiversity continues to decline. China is the world's top CO2 emitter, although per capita emissions are much lower than those of developed counties. On the positive side, large national conservation programs have been implemented, including the Natural Forest Conservation Program, the Grain-to-Green Program, Ecosystem Functional Conservation Areas, and Ecological Protection Redlines. More than 2,750 nature reserves have been established and a new national park system is being constructed. Some endangered and threatened species, such as the giant panda, are showing signs of recovery, and forest cover and some ecosystem services have increased. These mixed environmental outcomes result from human-nature interactions within China as well as between China and adjacent and distant countries. These include increasing rapid economic growth, resource consumption, land use change, trade and investment, and conservation and development policies. We suggest systems approaches such as nexus approaches and flow-centered governance to help China achieve ecological civilization and become an environmental leader on a metacoupled planet.

Description: Transformative governance is an approach to environmental governance that has the capacity to respond to, manage, and trigger regime shifts in coupled social-ecological systems (SESs) at multiple scales. The goal of transformative governance is to actively shift degraded SESs to alternative, more desirable, or more functional regimes by altering the structures and processes that define the system. Transformative governance is rooted in ecological theories to explain cross-scale dynamics in complex systems, as well as social theories of change, innovation, and technological transformation. Similar to adaptive governance, transformative governance involves a broad set of governance components, but requires additional capacity to foster new social-ecological regimes including increased risk tolerance, significant systemic investment, and restructured economies and power relations. Transformative governance has the potential to actively respond to regime shifts triggered by climate change, and thus future research should focus on identifying system drivers and leading indicators associated with social-ecological thresholds.

Description: In this review, we examine the debate surrounding the role for organic agriculture in future food production systems. Typically represented as a binary organic–conventional question, this debate perpetuates an either/or mentality. We question this framing and examine the pitfalls of organic–conventional cropping systems comparisons. The review assesses current knowledge about how these cropping systems compare across a range of metrics related to four sustainability goals: productivity, environmental health, economic viability, and quality of life. We conclude by arguing for reframing the debate, recognizing that farming systems fall along gradients between three philosophical poles—industrial, agrarian, and ecological—and that different systems will be appropriate in different contexts. Despite evidence for lower yields in organic crop systems, we found considerable evidence for environmental and social benefits. Given these advantages, and the potential for improving organic systems, we echo calls for increased investment in organic and ecologically based cropping systems research and extension.

Description: Future sea-level rise generates hazards for coastal populations, economies, infrastructure, and ecosystems around the world. The projection of future sea-level rise relies on an accurate understanding of the mechanisms driving its complex spatio-temporal evolution, which must be founded on an understanding of its history. We review the current methodologies and data sources used to reconstruct the history of sea-level change over geological (Pliocene, Last Interglacial, and Holocene) and instrumental (tide-gauge and satellite alimetry) eras, and the tools used to project the future spatial and temporal evolution of sea level. We summarize the understanding of the future evolution of sea level over the near (through 2050), medium (2100), and long (post-2100) terms. Using case studies from Singapore and New Jersey, we illustrate the ways in which current methodologies and data sources can constrain future projections, and how accurate projections can motivate the development of new sea-level research questions across relevant timescales.

Description: Access to electricity changes lives but only when people can afford electricity-powered services to meet their basic needs, and this is more than just two light bulbs and a fan. Decentralized renewable energy (RE) minigrids, particularly solar photovoltaic (PV) minigrids, can cost-effectively electrify a large share of currently unelectrified rural populations. But the cost of using appliances with this electricity is still much higher than what the poor can afford without deep subsidies. This affordability gap stunts the sustainability and growth of RE minigrids. Significant improvements in the economics of supplying electricity with minigrids, combined with higher-efficiency appliances, are needed to reduce the effective cost of using electricity in decentralized RE minigrids. These would bridge the affordability gap and improve business opportunities and value to users, investors, and service providers and thus create market-driven expansion to overcome the acute lack of funding that they currently face. Technology breakthroughs that can help in this respect include (a) significantly cheaper solar PV components to reduce up-front costs of solar PV minigrids; (b) significantly more affordable and energy-efficient appliances; (c) better-performing bulk storage at a significantly lower cost; (d) affordable and easy-to-use grid management solutions, and (e) a utility in a box for a simpler, cheaper, and faster way to set up minigrids.

Description: The goal of this article is to provide an introduction to basic modeling and simulation techniques for multiple interacting unmanned aerial vehicles (UAVs), called swarms, for applications in mapping. The target audience is senior students and young scientists. This review will serve to inform, orient, and direct someone already educated in environmental science but unaware of multiple-UAV interaction models.

Description: It has been estimated that one-third of global food is lost or wasted, entailing significant environmental, economic, and social costs. The scale and impact of food loss and waste (FLW) has attracted significant interest across sectors, leading to a relatively recent proliferation of publications. This article synthesizes existing knowledge in the literature with a focus on FLW measurement, drivers, and solutions. We apply the widely adopted DPSIR (Driver-Pressure-State-Impact-Response) framework to structure the review. Key takeaways include the following: Existing definitions of FLW are inconsistent and incomplete, significant data gaps remain (by food type, stage of supply chain, and region, especially for developing countries), FLW solutions focus more on proximate causes rather than larger systemic drivers, and effective responses to FLW will require complementary approaches and robust evaluation.

Description: This article takes stock of the evolution of the United Nations Framework Convention on Climate Change (UNFCCC) through the prism of three recent shifts: the move away from targeting industrial country emissions in a legally binding manner under the Kyoto Protocol to mandating voluntary contributions from all countries under the Paris Agreement; the shift from the top-down Kyoto architecture to the hybrid Paris outcome; and the broadening out from a mitigation focus under Kyoto to a triple goal comprising mitigation, adaptation, and finance under Paris. This review discusses the implications of these processes for the effectiveness, efficiency, and equity of the UNFCCC's institutional and operational settings for meeting the convention's objectives. It ends by sketching three potential scenarios facing the UNFCCC as it seeks to coordinate the Paris Agreement and its relationship to the wider landscape of global climate action.

Description: Rising inequalities and accelerating global environmental change pose two of the most pressing challenges of the twenty-first century. To explore how these phenomena are linked, we apply a social-ecological systems perspective and review the literature to identify six different types of interactions (or “pathways”) between inequality and the biosphere. We find that most of the research so far has only considered one-directional effects of inequality on the biosphere, or vice versa. However, given the potential for complex dynamics between socioeconomic and environmental factors within social-ecological systems, we highlight examples from the literature that illustrate the importance of cross-scale interactions and feedback loops between inequality and the biosphere. This review draws on diverse disciplines to advance a systemic understanding of the linkages between inequality and the biosphere, specifically recognizing cross-scale feedbacks and the multidimensional nature of inequality.

Description: Social media is changing how people connect, create, and share content and is an integral force shaping modern society. Given the significant environmental challenges society faces, this review considers (a) how social media is currently contributing to the development of a more sustainable society and (b) directions for future work such that researchers and practitioners may more effectively utilize this technology. At present, case studies, anecdotal evidence, and research demonstrate that social media is contributing to sustainability in diverse ways including behavioral interventions utilizing social media elements; social and political activism; supporting/generating sustainable business practices and addressing corporate “greenwashing”; increasing access to, and the potential quality of, environmental education; and through citizen science projects. Although this work is promising, there is an urgent need for further and more methodologically rigorous research, which evaluates the specific impacts of social media technology on sustainability outcomes, i.e., proenvironmental knowledge, attitudes, and—in particular—behavior.

Description: The global demand for water and energy is projected to grow, but there likely will be significant constraints in our ability to keep meeting it. These constraints will be imposed partly by the interdependence between water, energy, and climate change. If left unchecked, these connections can exacerbate water and energy shortages and aggravate climate change impacts: Energy is used to supply and treat water; moreover, emissions from energy generation contribute to climate change, which affects water supplies and increases the demand for energy to sustain Earth's growing population and economy. The linkage between water and energy can offer opportunities for better meeting expected demand while minimizing damage from shortages of either. This article focuses on the technological and engineering aspects of various connections in the water-energy nexus where advancements can enable greater supply of one or both. It also outlines the benefits and challenges associated with each connection.

Description: International policies for mitigation of climate change provide a global public good and thus suffer from “free riding,” i.e., inaction of governments. In 25 years of negotiations under the UN Framework Convention on Climate Change (UNFCCC), the regime has changed its character from a top-down approach based on mandatory emissions commitments to a bottom-up system of voluntary government pledges. At the same time, various initiatives by governments at all levels and private companies have been established, but most are limited to emissions reporting and exchange of knowledge on mitigation technologies. None of the alternatives has shown a higher mitigation effectiveness than the Kyoto Protocol. Generally, the transition toward a bottom-up regime risks a reduction of transparency and increases in the transaction costs of mitigation. Although it could give rise to a club of countries engaging in strong mitigation that could expand over time, it is unlikely to be ambitious enough to achieve the target of limiting warming to 2°C. On the one hand, carbon prices will be applied in a larger number of jurisdictions, and mitigation technologies diffuse around the world. On the other hand, carbon price levels will remain relatively low, and their mitigation benefits will be more than outweighed by the growth of infrastructure and consumption. Thus, a temperature increase of at least 3°C by 2100 becomes more and more likely.

Description: The European Union (EU) is influential in environmental politics and policy-making across its 28 member states, around its periphery, and globally. Building on a diverse analytical and empirical literature, this article's seven sections each highlights important research findings and outcomes from more than four decades of EU environmental governance. These include (a) a substantial transfer of legal authority from member states to the supranational level; (b) a growing involvement of EU bodies, advocacy groups, and civil society in regional goal-setting and decision-making; (c) the development of elaborate governance systems and mechanisms for making, implementing, and enforcing policy; (d) EU exercise of considerable influence over countries seeking membership before and after joining the Union; (e) increased EU participation and influence in international fora; (f) a mixed record of uneven implementation and varied environmental outcomes in Europe and across the world; and (g) continuing challenges in nascent attempts to engender greater resource efficiency and sustainability in Europe and beyond. All of these findings and outcomes suggest numerous areas and directions for additional research.

Description: Increased interest in oceans is leading to new and renewed global governance efforts directed toward ocean issues in areas of food production, biodiversity conservation, industrialization, global environmental change, and pollution. Global oceans governance efforts face challenges and opportunities related to the nature of oceans and to actors involved in, the scale of, and knowledge informing their governance. We review these topics generally and in relation to nine new and emerging issues: small-scale fisheries (SSFs), aquaculture, biodiversity conservation on the high seas, large marine protected areas (LMPAs), tuna fisheries, deep-sea mining, ocean acidification (OA), blue carbon (BC), and plastics pollution.

Description: This article begins with a review and synthesis of some of the key theories, scholars, case examples, debates, methods, and (multiple) interpretations of environmental justice (EJ), as well as its expansion and globalization. We then look to some newly emerging themes, actions, and strategies for EJ and just sustainabilities. First, we look at the practices and materials of everyday life, illustrated by food and energy movements; second, the ongoing work on community and the importance of identity and attachment, informed by urban planning, food, and climate concerns; third, the growing interest in the relationship between human practices and communities and nonhuman nature. We also expand on the longstanding interest in just sustainabilities within this movement, illustrated by a wide range of concerns with food, energy, and climate justice. These new areas of work illustrate both recent developments and a set of paths forward for both the theory and practice of EJ.

Description: We outline the frameworks that shape and hold apart waste debates in and about the Global North and Global South and that hinder analysis of flows between them. Typically, waste is addressed as municipal waste, resulting in a focus on domestic consumption and urban governance and an emphasis on cities and the national scale. The prevailing ways of addressing the increasingly global flows of wastes between the North and South are those of global environmental justice and are underpinned by the geographical imagination encoded in the Basel Convention. New research on the trades in used goods and recycling in lower income countries challenges these accounts. It shows that arguments about dumping on the South need revision. Wastes are secondary resources for lower income countries, harvesting them is a significant economic activity, and consequent resource recovery is a key part of the global economy. Four areas for future research are identified: (a) changing patterns of global harvesting, (b) attempts to rescale resource recovery and the challenges faced, (c) the geopolitics of resource recovery, and (d) changes in resource recovery in lower income countries.

Description: Materials production requires a large amount of energy use and is a significant source of greenhouse gas (GHG) emissions, producing approximately 25% of all anthropogenic CO2 emissions. It produces large volumes of waste both in production and at end-of-life disposal. More efficient use of materials could play a key role in achieving multiple environmental and economic benefits. Material efficiency entails the pursuit of technical strategies, business models, consumer preferences, and policy instruments that would lead to a substantial reduction in the production of new materials required to deliver well-being. Although many opportunities exist, material efficiency is not realized in practice to its full potential. We evaluate the potential for material efficiency improvement, highlight the drivers to realize material efficiency, and anticipate ways forward to realize the potential of dematerializing our lives and the economy to limit the impacts of climate change and remain on a sustainable development path.

Description: This review examines the relationships between politics, sustainability, and development. Following an overview of sustainability thinking across different traditions, the politics of resources and the influence of scarcity narratives on research, policy and practice are explored. This highlights the politics of transformations and the way these play out under combinations of technology-led, market-led, state-led, and citizen-led processes. In particular, this review points to the politics of alliance building and collective action for sustainability and development. Transformations cannot be managed or controlled, but must draw on an unruly politics, involving diverse knowledges and multiple actors. This review highlights how politics are articulated through regimes of truth, rule, and accumulation, and how understanding such political processes has implications for institutional and governance responses. The conclusion reflects on future research priorities and the methodological stance required for an effective response to the political challenges of sustainability and development.

Description: Within the past decade, the attribution of extreme weather and climate events has emerged from a theoretical possibility into a subfield of climate science in its own right, providing scientific evidence on the role of anthropogenic climate change in individual extreme weather events, on a regular basis and using a range of approaches. Different approaches and thus different framings of the attribution question lead to very different assessments of the role of human-induced climate change. Although there is no right or wrong approach, the community is currently debating about the appropriate methodologies for addressing various stakeholder needs and scientific limitations. Tackling these limitations with more thorough model evaluation and meaningful bias corrections as well as going beyond the meteorological hazard and attributing the full impacts of extreme weather are the main challenges to face in the coming years.

Description: The article describes the field of sustainability transitions research, which emerged in the past two decades in the context of a growing scientific and public interest in large-scale societal transformation toward sustainability. We describe how different scientific approaches and methodological positions explore diverse types of transitions and provide the basis for multiple theories and models for governance of sustainability transitions. We distinguish three perspectives in studying transitions: socio-technical, socio-institutional, and socio-ecological. Although the field as a whole is very heterogeneous, commonalities can be characterized in notions such as path dependencies, regimes, niches, experiments, and governance. These more generic concepts have been adopted within the analytical perspective of transitions, which has led three different types of approaches to dealing with agency in transitions: analytical, evaluative, and experimental. The field has by now produced a broad theoretical and empirical basis along with a variety of social transformation strategies and instruments, impacting disciplinary scientific fields as well as (policy) practice. In this article, we try to characterize the field by identifying its main perspectives, approaches and shared concepts, and its relevance to real-world sustainability problems and solutions.

Description: Systematic conservation planning (SCP) is a rapidly advancing discipline aimed at providing decision support for choices between alternate conservation actions. SCP is often used to inform choices about areas to protect, in order to optimize outcomes for biodiversity while minimizing societal costs. Despite the widespread application of SCP approaches, there is limited understanding of the types of impacts resulting from related projects, and when and where it is most effective. This is compounded by the absence of a standardized approach to evaluating and reporting on the outcomes of SCP projects. We highlight the challenges of undertaking evaluations of complex planning processes, the current state of knowledge about the outcomes of SCP projects, and emerging opportunities to improve evaluation. There is a need for clarity around theories of change, definitions of SCP and impact, and standardized reporting and information sharing across the discipline.

Description: Existing technologies, institutions, and behavioral norms together act to constrain the rate and magnitude of carbon emissions reductions in the coming decades. The inertia of carbon emissions due to such mutually reinforcing physical, economic, and social constraints is referred to as carbon lock-in. Carbon lock-in is a special case of path dependency, which is common in the evolution of complex systems. However, carbon lock-in is particularly prone to entrenchment given the large capital costs, long infrastructure lifetimes, and interrelationships between the socioeconomic and technical systems involved. Further, the urgency of efforts to avoid dangerous climate change exacerbates the liability of even small lock-in risks. Although carbon lock-in has been recognized for years, efforts to characterize the types and causes of carbon lock-in, or to quantitatively assess and evaluate its policy implications, have been limited and scattered across a number of different disciplines. This systematic review of the literature synthesizes what is known about the types and causes of carbon lock-in, including the scale, magnitude, and longevity of the effects, and policy implications. We identify three main types of carbon lock-in and describe how they coevolve: (a) infrastructural and technological, (b) institutional, and (c) behavioral. Although each type of lock-in has its own set of processes, all three are tightly intertwined and contribute to the inertia of carbon emissions. We outline the conditions, opportunities, and strategies for fostering transitions toward less-carbon-intensive emissions trajectories. We conclude by proposing a carbon lock-in research agenda that can help bridge the gaps between science, knowledge, and policy-making.

Description: We review the challenges and future perspectives of regional climate model (RCM), or dynamical downscaling, activities. Among the main technical issues in need of better understanding are those of selection and sensitivity to the model domain and resolution, techniques for providing lateral boundary conditions, and RCM internal variability. The added value (AV) obtained with the use of RCMs remains a central issue, which needs more rigorous and comprehensive analysis strategies. Within the context of regional climate projections, large ensembles of simulations are needed to better understand the models and characterize uncertainties. This has provided an impetus for the development of the Coordinated Regional Downscaling Experiment (CORDEX), the first international program offering a common protocol for downscaling experiments, and we discuss how CORDEX can address the key scientific challenges in downscaling research. Among the main future developments in RCM research, we highlight the development of coupled regional Earth system models and the transition to very high-resolution, cloud-resolving models.

Description: Rewilding is being promoted as an ambitious alternative to current approaches to nature conservation. Interest is growing in popular and scientific literatures, and rewilding is the subject of significant comment and debate, outstripping scientific research and conservation practice. Projects and research are found the world over, with concentrations in Europe, North America, and on tropical islands. A common aim is to maintain, or increase, biodiversity, while reducing the impact of present and past human interventions through the restoration of species and ecological processes. The term rewilding has been applied to diverse concepts and practices. We review the historical emergence of the term and its various overlapping meanings, aims, and approaches, and illustrate this through a description of four flagship rewilding case studies. The science of rewilding has centered on three different historical baselines: the Pleistocene, the Holocene, and novel contemporary ecosystems. The choice of baseline has differing implications for conservation in a variety of contexts. Rewilding projects involve a range of practical components—such as passive management, reintroduction, and taxon substitution—some of which have attracted criticism. They also raise a series of political, social, and ethical concerns where they conflict with more established forms of environmental management. In conclusion, we summarize the different goals, approaches, tools, and contexts that account for the variations in rewilding and identify priorities for future research and practice.

Description: Life on Earth comes in many forms, but all life-forms share a common element in carbon. It is the basic building block of biology, and by trapping radiation it also plays an important role in maintaining the Earth's atmosphere at a temperature hospitable to life. Like all matter, carbon can neither be created nor destroyed, but instead is continuously exchanged between ecosystems and the environment through a complex combination of physics and biology. In recent decades, these exchanges have led to an increased accumulation of carbon on the land surface: the terrestrial carbon sink. Over the past 10 years (2007–2016) the sink has removed an estimated 3.61 Pg C year−1 from the atmosphere, which amounts to 33.7% of total anthropogenic emissions from industrial activity and land-use change. This sink constitutes a valuable ecosystem service, which has significantly slowed the rate of climate change. Here, we review current understanding of the underlying biological processes that govern the terrestrial carbon sink and their dependence on climate, atmospheric composition, and human interventions.

Description: Environmental problems can be reduced if people more consistently engage in proenvironmental actions. In this article, I discuss factors that motivate or inhibit individuals to act proenvironmentally. Many people are intrinsically motivated to engage in proenvironmental actions, because protecting the environment makes them feel good about themselves. People are more likely to be intrinsically motivated to act proenvironmentally over and again when they strongly endorse biospheric values. However, people may be less likely to act on their biospheric values when these values are not supported by the context, or when competing values are activated by factors in a choice context. Next, I discuss strategies to encourage proenvironmental actions by strengthening biospheric values, or by empowering and motivating people to act on their biospheric values. Moreover, I discuss factors influencing the acceptability of environmental policies that aim to encourage proenvironmental behavior.

Description: Urbanization is one of the biggest social transformations of modern time, driving and driven by multiple social, economic, and environmental processes. The impacts of urbanization on the environment are profound, multifaceted and are manifested at the local, regional, and global scale. This article reviews recent advances in conceptual and empirical knowledge linking urbanization and the environment, focusing on six core aspects: air pollution, ecosystems, land use, biogeochemical cycles and water pollution, solid waste management, and the climate. We identify several emerging trends and remaining questions in urban environmental research, including (a) increasing evidence on the amplified or accelerated environmental impacts of urbanization; (b) varying distribution patterns of impacts along geographical and other socio-economic gradients; (c) shifting focus from understanding and quantifying the impacts of urbanization toward understanding the processes and underlying mechanisms; (d) increasing focus on understanding complex interactions and interlinkages among different environmental, social, economic, and cultural processes; and (e) conceptual advances that call for articulating and using a systems approach in cities. In terms of governing the urban environment, there is an increasing focus on public participation and coproduction of knowledge with stakeholders. Cities are actively experimenting toward sustainability under a plethora of guiding concepts that manifests their aspirational goals, with varying levels of implementation and effectiveness.

Description: Human interactions with wildlife are a defining experience of human existence. These interactions can be positive or negative. People compete with wildlife for food and resources, and have eradicated dangerous species; co-opted and domesticated valuable species; and applied a wide range of social, behavioral, and technical approaches to reduce negative interactions with wildlife. This conflict has led to the extinction and reduction of numerous species and uncountable human deaths and economic losses. Recent advances in our understanding of conflict have led to a growing number of positive conservation and coexistence outcomes. I summarize and synthesize factors that contribute to conflict, approaches that mitigate conflict and encourage coexistence, and emerging trends and debates. Fertile areas for scholarship include scale and complexity, models and scenarios, understanding generalizable patterns, expanding boundaries of what is considered conflict, using new tools and technologies, information sharing and collaboration, and the implications of global change. The time may be ripe to identify a new field, anthrotherology, that brings together scholars and practitioners from different disciplinary perspectives to address human–wildlife conflict and coexistence.

Description: Intertidal mangrove forests are a dynamic ecosystem experiencing rapid changes in extent and habitat quality over geological history, today and into the future. Climate and sea level have drastically altered mangrove distribution since their appearance in the geological record ∼75 million years ago (Mya), through to the Holocene. In contrast, contemporary mangrove dynamics are driven primarily by anthropogenic threats, including pollution, overextraction, and conversion to aquaculture and agriculture. Deforestation rates have declined in the past decade, but the future of mangroves is uncertain; new deforestation frontiers are opening, particularly in Southeast Asia and West Africa, despite international conservation policies and ambitious global targets for rehabilitation. In addition, geological and climatic processes such as sea-level rise that were important over geological history will continue to influence global mangrove distribution in the future. Recommendations are given to reframe mangrove conservation, with a view to improving the state of mangroves in the future.

Description: Well into the 21st century, safe and affordable drinking water remains an unmet human need. At least 1.8 billion people are potentially exposed to microbial contamination, and close to 140 million people are potentially exposed to unsafe levels of arsenic. Many new technologies, water quality assessments, health impact assessments, cost studies, and user preference studies have emerged in the past 20 years to further the laudable goal of safe drinking water for all. This article reviews (a) the current literature on safe water approaches with respect to their effectiveness in improving water quality and protectiveness in improving human health, (b) new work on the uptake and use of safe water systems among low-income consumers, (c) new research on the cash and labor costs of safe water systems, and (d) research on user preferences and valuations for safe water. Our main recommendation is that safe water from “source to sip” should be seen as a system; this entire system, rather than a discrete intervention, should be the object of analysis for technical, economic, and health assessments.

Description: New partnerships between governments, private companies, and nongovernmental organizations (NGOs) are reshaping global environmental governance. In particular, there has been a rise of voluntary sustainability standards in an attempt to manage social and environmental impacts of global supply chains. We analyze the large spectrum of interactions between private, public, and civil society actors around voluntary sustainability standards, primarily for tropical agriculture and forestry. This review uncovers a policy ecosystem dominated by a proliferation of standards that complement, substitute, or compete against each other, with coordination mechanisms beginning to arise. Contrary to widely held views, interactions between governments, NGOs, and private companies surrounding the adoption of sustainable practices are not generally antagonistic, and public and private environmental governance regimes rarely operate independently. The influence of these interactions on the effectiveness of sustainability standards needs more attention. Better understanding how private regulations interact with the policy ecosystem will help design more effective interventions.

Description: Risk analysis of species invasions links biology and economics, is increasingly mandated by international and national policies, and enables improved management of invasive species. Biological invasions proceed through a series of transition probabilities (i.e., introduction, establishment, spread, and impact), and each of these presents opportunities for management. Recent research advances have improved estimates of probability and associated uncertainty. Improvements have come from species-specific trait-based risk assessments (of estimates of introduction, establishment, spread, and impact probabilities, especially from pathways of commerce in living organisms), spatially explicit dispersal models (introduction and spread, especially from transportation pathways), and species distribution models (establishment, spread, and impact). Results of these forecasting models combined with improved and cheaper surveillance technologies and practices [e.g., environmental DNA (eDNA), drones, citizen science] enable more efficient management by focusing surveillance, prevention, eradication, and control efforts on the highest-risk species and locations. Bioeconomic models account for the interacting dynamics within and between ecological and economic systems, and allow decision makers to better understand the financial consequences of alternative management strategies. In general, recent research advances demonstrate that prevention is the policy with the greatest long-term net benefit.

Description: Conceptual confusion revolves around how to define, assess, and overcome land, ecosystem, and landscape degradation. Common elements link degradation and recovery processes, offering ways to advance local, regional, and global initiatives to reduce degradation and promote the recovery of ecosystems and landscapes in forest biomes. Biophysical attributes of degradation and recovery can be measured, but the relevance of selected attributes across scales is subject to values that determine preferred states. Degradation defined in the context of a resilience-based approach is a state where the capacity for regeneration is greatly reduced or lost, recovery is arrested, core interactions and feedbacks are broken, and human intervention is required to initiate a trajectory of recovery. Another approach combines degradation and recovery processes through the concept of recovery debt, the cumulative lost benefits incurred, relative to a target state during phases of degradation and recovery. Degradation and recovery can also be described in terms of societal willingness to invest in improved management or restoration. Interventions can facilitate recovery to new stable or persistent states that provide multiple social and ecological benefits at land, ecosystem, and landscape scales. Multiple trajectories of recovery, as well as historic and ongoing chronic environmental change, might, however, mean that recovery to an original reference state is not possible.

Description: The growing extraction of natural resources and the waste and emissions resulting from their use are directly or indirectly responsible for humanity approaching or even surpassing critical planetary boundaries. A sound knowledge base of society's metabolism, i.e., the physical exchange processes between society and its natural environment and the production and consumption processes involved, is essential to develop strategies for more sustainable resource use. Economy-wide material flow accounting (MFA) is a framework that provides consistent compilations of the material inputs to national economies, changes in material stocks within the economic system, and material outputs to other economies and the environment. We present the conceptual foundations of MFA and derived indicators and review the current state of knowledge of global patterns and trends of extraction, trade, and use of materials. We discuss the relation of material use and economic development and the decoupling of material use from economic growth in the context of sustainable resource use policies.

Description: Climate change represents the most significant challenge of the twenty-first century and poses risks to water and sanitation services. Concerns for water supply include damage to infrastructure from flooding, loss of water sources due to declining rainfall and increasing demand, and changes in the water quality of water sources and within distribution of water. Sanitation concerns include damage and loss of services from floods and reduced carrying capacity of waters receiving wastewater. Key actions to reduce climate risks include the integration of measures of climate resilience into water safety plans, as well as improved accounting and management of water resources. Policy prescriptions on technologies for service delivery and changes in management models offer potential to reduce risks, particularly in low-income settings. Water and sanitation services contribute to greenhouse gas emissions. Choice of wastewater treatment technologies, improved pumping efficiency, use of renewable sources of energy, and within-system generation of energy offer potential for reducing emissions. Overall, greater attention and research are required to understand, plan for, and adapt to climate change in water and sanitation services. As with many other climate change adaptations, the likely benefits from no-regrets solutions are likely to outweigh the costs of investment.

Description: Weather and climate extremes impose serious impacts on natural and human systems. In its fifth assessment report (AR5) and a special report [Managing the Risks of Extreme Events and Disasters to Advance Climate Change Adaptation (SREX)], the Intergovernmental Panel on Climate Change provided a thorough assessment of observed and projected changes in extremes in a warming climate, with evidenced scientific gaps in the understanding of these responsive changes being reported. Reviewing post-AR5 literature, this article synthesizes recent advances regarding these previous gaps with respect to detection, attribution, and projection of extremes. We focus on constraints for the assessment confidence, overlooked types and characteristics of extremes, and changes in their thermodynamic-dynamic drivers. We also stress potential misinterpretations of existing results, propose an update of earlier key findings, and identify burgeoning topics.

Description: Human actions are transforming ecosystems across the globe. Six frameworks aid in understanding the forces that drive human stress on the environment and human responses to this stress. Two of them, the stochastic impacts by regression on population, affluence and technology (STIRPAT) model and decomposition analysis, are approaches to analyzing data. Four describe the interrelated system of human actions and environmental responses: driving forces, pressures, states, impacts, responses (DPSIR); the Millennium Ecosystem Assessment (MA) framework; coupled human and natural systems (CHANS) and telecoupling; and social-ecological systems (SES). In applying these frameworks, attention must be given to the scale of analysis and to the effects of context. In addition to the frameworks there are four substantial research literatures providing theory and empirical analysis of how drivers place stress on the environment: a macrocomparative tradition, work on household energy consumption, land change science, and research on commons. Although these traditions remain somewhat separate, they are largely complementary.

Description: Illegal wildlife trade (IWT) has increased in profile in recent years as a global policy issue, largely because of its association with declines in prominent internationally trafficked species. In this review, we explore the scale of IWT, associated threats to biodiversity, and appropriate responses to these threats. We discuss the historical development of IWT research and highlight the uncertainties that plague the evidence base, emphasizing the need for more systematic approaches to addressing evidence gaps in a way that minimizes the risk of unethical or counterproductive outcomes for wildlife and people. We highlight the need for evaluating interventions in order to learn, and the importance of sharing datasets and lessons learned. A more collaborative approach to linking IWT research, practice, and policy would better align public policy discourse and action with research evidence. This in turn would enable more effective policy making that contributes to reducing the threat to biodiversity that IWT represents.

Description: The assessment literature on climate change solutions to date has emphasized technologies and options based on cost-effectiveness analysis. However, many solutions to climate change mitigation misalign with such analytical frameworks. Here, we examine demand-side solutions, a crucial class of mitigation options that go beyond technological specification and cost-benefit analysis. To do so, we synthesize demand-side mitigation options in the urban, building, transport, and agricultural sectors. We also highlight the specific nature of demand-side solutions in the context of development. We then discuss key analytical considerations to integrate demand-side options into overarching assessments on mitigation. Such a framework would include infrastructure solutions that interact with endogenous preference formation. Both hard infrastructures, such as the built environment, and soft infrastructures, such as habits and norms, shape behavior and as a consequence offer significant potential for reducing overall energy demand and greenhouse gas emissions. We conclude that systemic infrastructural and behavioral change will likely be a necessary component of a transition to a low-carbon society.

Description: Environmental movements are networks of informal interactions that may include individuals, groups, and organizations engaged in collective action motivated by shared identity or concern about environmental issues. This article reviews literature on environmental movements (including antinuclear energy movements) according to four main aspects: the social bases and values underlying the movements' mobilization, the resources supporting their mobilization, the political opportunities channeling their mobilization, and the cultural framing processes through which environmental issues are defined as social and political problems to be addressed through mobilization. In addition, we consider the historical antecedents and roots of environmental movements. Finally, we discuss the interplay between the local and the global levels and the movements' impacts, a long neglected issue in the social movement literature. Our review highlights three main features of environmental movements: they are heterogeneous; they have profoundly transformed themselves; and they have generally become more institutionalized.

Description: Peatlands are wetland ecosystems that accumulate dead organic matter (i.e., peat) when plant litter production outpaces peat decay, usually under conditions of frequent or continuous waterlogging. Collectively, global peatlands store vast amounts of carbon (C), equaling if not exceeding the amount of C in the Earth's vegetation; they also encompass a remarkable diversity of forms, from the frozen palsa mires of the northern subarctic to the lush swamp forests of the tropics, each with their own characteristic range of fauna and flora. In this review we explain what peatlands are, how they form, and the contribution that peatland science can make to our understanding of global change. We explore the variety in formation, shape, vegetation type, and chemistry of peatlands across the globe and stress the fundamental features that are common to all peat-forming ecosystems. We consider the impacts that past, present, and future environmental changes, including anthropogenic disturbances, have had and will have on peatland systems, particularly in terms of their important roles in C storage and the provision of ecosystem services. The most widespread uses of peatlands today are for forestry and agriculture, both of which require drainage that results in globally significant emissions of carbon dioxide (CO2), a greenhouse gas (GHG). Climatic drying and drainage also increase the risk of peat fires, which are a further source of GHG emissions [CO2 and methane (CH4)] to the atmosphere, as well as causing negative human health and socioeconomic impacts. We conclude our review by explaining the roles that paleoecological, experimental, and modeling studies can play in allowing us to build a more secure understanding of how peatlands function, how they will respond to future climate- and land-management-related disturbances, and how best we can improve their resilience in a changing world.