ALBERT

Description: Abstract Aim Alexander von Humboldt observed that plant communities on different continents but under similar climatic conditions shared few common species but often contained representatives of the same genera or higher taxonomic groups. To test if this observation can be extended to substrate type, we explored whether a phylogenetic signature could be seen among floras growing on ultramafic substrates that present challenging edaphic conditions for plant growth and are well‐known for their distinctive vegetation. Location Cuba, Madagascar, New Caledonia. Taxon Angiosperms. Methods We compared the floras of Cuba, Madagascar and New Caledonia to test whether the same plant families were under‐ or over‐represented on the ultramafic substrates of the three islands. Results Pairwise comparisons showed that plant orders and families tended to have the same behaviour on the three islands, i.e. ultramafic substrates filtered (in favour of or against) the same plant groups in the three biogeographical distinct areas. The COM clade (comprising Celastrales, Oxalidales and Malpighiales) appears to be over‐represented on ultramafic substrates in all three islands and contains over half of the world's known nickel hyperaccumulators. Main conclusions Our analyses provide support for Humboldt's observation by showing that ecological sorting can favour the same plant lineages in similar environments in different biogeographical regions.

Description: The projected impact of 1.5 and 2.0°C warming above the pre‐industrial period on wheat production varies spatially; a larger increase is projected for temperate high rainfall regions than for moderate hot low rainfall and irrigated regions. Grain yields in warmer regions are more likely to be reduced than in cooler regions. Despite mostly positive impacts on global average grain yields, the frequency of extremely low yields and yield inter‐annual variability will increase under both warming scenarios for some of the hot growing locations, including locations from the second largest global wheat producer—India, which supplies more than 14% of global wheat. The projected global impacts of warming of 〈2°C on wheat production is therefore not evenly distributed and will affect regional food security across the globe as well as food prices and trade. Abstract Efforts to limit global warming to below 2°C in relation to the pre‐industrial level are under way, in accordance with the 2015 Paris Agreement. However, most impact research on agriculture to date has focused on impacts of warming 〉2°C on mean crop yields, and many previous studies did not focus sufficiently on extreme events and yield interannual variability. Here, with the latest climate scenarios from the Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) project, we evaluated the impacts of the 2015 Paris Agreement range of global warming (1.5 and 2.0°C warming above the pre‐industrial period) on global wheat production and local yield variability. A multi‐crop and multi‐climate model ensemble over a global network of sites developed by the Agricultural Model Intercomparison and Improvement Project (AgMIP) for Wheat was used to represent major rainfed and irrigated wheat cropping systems. Results show that projected global wheat production will change by −2.3% to 7.0% under the 1.5°C scenario and −2.4% to 10.5% under the 2.0°C scenario, compared to a baseline of 1980–2010, when considering changes in local temperature, rainfall, and global atmospheric CO2 concentration, but no changes in management or wheat cultivars. The projected impact on wheat production varies spatially; a larger increase is projected for temperate high rainfall regions than for moderate hot low rainfall and irrigated regions. Grain yields in warmer regions are more likely to be reduced than in cooler regions. Despite mostly positive impacts on global average grain yields, the frequency of extremely low yields (bottom 5 percentile of baseline distribution) and yield inter‐annual variability will increase under both warming scenarios for some of the hot growing locations, including locations from the second largest global wheat producer—India, which supplies more than 14% of global wheat. The projected global impact of warming 〈2°C on wheat production is therefore not evenly distributed and will affect regional food security across the globe as well as food prices and trade.

Description: Abstract Stable oxygen isotopes (δ18O) in the Bona‐Churchill (B‐C) ice core from southeast Alaska provide a valuable, high‐resolution history of climate variability and sea ice cover in the western Arctic over the last 800 years. Multiple ice cores have been collected from the Wrangell‐St. Elias Mountain Range; however, their δ18O records exhibit little consistency as each core offers a unique view on local, regional, and/or global climate variability. To explore the primary mechanisms influencing the isotopic signature at the B‐C site, we utilize isotope‐enabled model data, reanalysis data, and observations, which all indicate a strong connection between isotopes at the B‐C site and western Arctic climate, likely established by the location of the storm track in this region. Enriched B‐C δ18O reflects increased southerly flow and warmer waters in the Bering Sea, which modulates the heat flux through the Bering Strait and into the Arctic, thereby affecting sea ice cover in the western Arctic. The B‐C δ18O paleorecord shares some remarkable similarities (r = −0.80, p 〈 .001) with the duration of western arctic sea ice cover reconstructed from a Chukchi Sea sediment core. Interestingly, during the Little Ice Age, enriched δ18O and reduced western Arctic sea ice are observed and may be indicative of prolonged periods of the warm Arctic/cold continents pattern and a northwestward shift of the North Pacific storm track.

Description: Organismal and community-wide responses of reef-building corals are documented before and after a severe cold-water thermal anomaly that occurred in 2010 in the Florida Keys, USA. In January 2010 seawater temperatures dropped far below the normal minima (to 〈11°C), resulting in the largest documented coral mass mortality event ever recorded in the Florida Keys. Physiological measurements demonstrated species-specific thermal sensitivities to this environmental perturbation. Four common corals with narrow thermal tolerance, Acropora cervicornis , Orbicella annularis, O. faveolata, and Porites astreoides, sustained high mortality (〉80%) on inshore reefs. In contrast, another common coral with a wide thermal tolerance, Siderastrea siderea, was not affected by this cold anomaly. We measured biomass, symbiotic algal densities (genus: Symbiodinium ), chlorophyll a content, and maximum quantum efficiency of photosystem II for reef-building corals on a seasonal basis before and after the 2010 cold anomaly. Our data document a clear correspondence between physiological response, biomass levels, and survivorship among these five scleractinian coral species. These physiological findings are mirrored by in-shore benthic community monitoring data, which show the dramatic loss of the three cold-sensitive species and continued survival of the cold-tolerant species. Finally, we document recruitment and survival rates of newly settled reef-building corals on four inshore reefs, which experienced high coral mortality during the 2010 cold-kill. Interestingly, both a cold-tolerant species, S. siderea, and a cold-intolerant species, P. astreoides, were the most abundant species recruiting to these postdisturbance reefs.

Description: How climate constrains species’ distributions through time and space is an important question in the context of conservation planning for climate change. Despite increasing awareness of the need to incorporate mechanism into species distribution models (SDMs), mechanistic modelling of endotherm distributions remains limited in the current literature. Using the American pika ( Ochotona princeps ) as an example, we present a framework whereby mechanism can be incorporated into endotherm SDMs. Pika distribution has repeatedly been found to be constrained by warm temperatures, so we used Niche Mapper, a mechanistic heat-balance model, to convert macroclimate data to pika-specific surface-activity time in summer across the western United States. We then explored the difference between using a macroclimate predictor (summer temperature) and using a mechanistic predictor (predicted surface-activity time) in SDMs. Both approaches accurately predicted pika presences in current and past climate regimes. However, the activity models predicted 8-19% less habitat loss in response to annual temperature increases of ~3-5°C predicted in the region by 2070, suggesting that pikas may be able to buffer some climate-change effects through behavioral thermoregulation that can be captured by mechanistic modeling. Incorporating mechanism added value to the modeling by providing increased confidence in areas where different modeling approaches agreed and providing a range of outcomes in areas of disagreement. It also provided a more proximate variable relating animal distribution to climate, allowing investigations into how unique habitat characteristics and intraspecific phenotypic variation may allow pikas to exist in areas outside those predicted by generic SDMs. Only a small number of easily obtainable data are required to parameterize this mechanistic model for any endotherm, and its use can improve SDM predictions by explicitly modeling a widely applicable direct physiological effect: climate-imposed restrictions on activity. This more complete understanding is necessary to inform climate-adaptation actions, management strategies, and conservation plans. This article is protected by copyright. All rights reserved.

Description: Agriculture satisfies the basic need of society to produce food but must do so without undermining the world's capacity to sustain future food production and ecosystem services (Foley et al ., 2011; Rockström et al ., 2009; Foley et al ., 2005). Operating on a planet with finite resources and boundaries, agriculture must operate within three limits (Beddington et al ., 2012); 1) the quantity of food supply that can be produced under a given climate, 2) the quantity of food demanded by a growing and economically changing population, and 3) the impact of food production on the environment. Currently, agriculture and land-use change (LUC) are responsible for ~1/4 of total greenhouse gas (GHG) emissions from human activities (Smith et al ., 2014). As the human population grows, and is projected to move toward a more animal-based diet, it is projected that crop- and livestock production need to increase by 48% and 80% by 2050, respectively (FAO, 2006). It has been suggested that this could elevate agricultural non-CO 2 emissions 76% by 2050 relative to 1995 (Popp et al ., 2010). Yet agriculture has large potentials for mitigating climate change, even at relatively low cost (Smith et al ., 2014; Smith et al ., 2008; Nabuurs et al ., 2007; Schneider & Smith, 2009). This article is protected by copyright. All rights reserved.

Description: In order to better understand the tectonic evolution of the North American continent, we utilize data from the EarthScope Transportable Array network to calculate a 3-dimensional shear-velocity model for the continental United States. This model was produced through the inversion of Rayleigh wave phase velocities calculated using ambient noise tomography and wave gradiometry, which allows for sensitivity to a broad depth range. Shear velocities within this model highlight the influence of orogenic and post-orogenic events on the evolution of the lithosphere. Most notable is the contrast in crustal and upper mantle structure between the relatively slow western and relatively fast eastern North America. These differences are unlikely to stem solely from thermal variations within the lithosphere and highlight both the complexities in lithospheric structure across the continental US and the varying impacts that orogeny can have on the crust and upper mantle.

Description: Forecasting the consequences of climate change is contingent upon our understanding of the relationship between biodiversity patterns and climatic variability. While the impacts of climate change on individual species have been well-documented, there is a paucity of studies on climate-mediated changes in community dynamics. Our objectives were to investigate the relationship between temporal turnover in avian biodiversity and changes in climatic conditions and to assess the role of landscape fragmentation in affecting this relationship. We hypothesized that community turnover would be highest in regions experiencing the most pronounced changes in climate, and that these patterns would be reduced in human-dominated landscapes. To test this hypothesis, we quantified temporal turnover in avian communities over a 20-year period using data from the New York State Breeding Atlases collected during 1980-85 and 2000-05. We applied Bayesian spatially-varying intercept models to evaluate the relationship between temporal turnover and temporal trends in climatic conditions and landscape fragmentation. We found that models including interaction terms between climate change and landscape fragmentation were superior to models without the interaction terms; suggesting that the relationship between avian community turnover and changes in climatic conditions was affected by the level of landscape fragmentation. Specifically, we found weaker associations between temporal turnover and climatic change in regions with prevalent habitat fragmentation. We suggest that avian communities in fragmented landscapes are more robust to climate change than communities found in contiguous habitats because they are comprised of species with wider thermal niches and thus are less susceptible to shifts in climatic variability. We conclude that highly fragmented regions are likely to undergo less pronounced changes in composition and structure of faunal communities as a result of climate change, whereas those changes are likely to be greater in contiguous and unfragmented habitats. This article is protected by copyright. All rights reserved.

Description: Few estimates of migration rates or descriptions of behaviour or survival exist for wild populations of outmigrating Pacific salmon smolts from natal freshwater rearing areas to the ocean. Using acoustic transmitters and fixed receiver arrays across four years (2010-2013), we tracked the migration of 〉1,850 wild sockeye salmon ( Oncorhynchus nerka ) smolts from Chilko Lake, British Columbia to the coastal Pacific Ocean (〉1,000 km distance). Cumulative survival to the ocean ranged 3-10% among years, although this may be slightly underestimated due to technical limitations at the final receiver array. Distinct spatial patterns in both behaviour and survival were observed through all years. In small, clear, upper-river reaches, downstream migration largely occurred at night at speeds up to 50 km d −1 and coincided with poor survival. Among years, only 57-78% of smolts survived the first 80 km. Parallel laboratory experiments revealed excellent short-term survival and unhindered swimming performance of dummy-tagged smolts, suggesting that predators rather than tagging effects were responsible for the initial high mortality of acoustic-tagged smolts. Migration speeds increased in the Fraser River mainstem (~220 km d −1 in some years), diel movement patterns ceased, and smolt survival generally exceeded 90% in this segment. Marine movement rates and survival were variable across years, with among-year segment-specific survival being the most variable and lowest (19-61%) during the final (and longest – 240 km) marine migration segment. Osmoregulatory preparedness was not expected to influence marine survival, as smolts could maintain normal levels of plasma chloride when experimentally exposed to saltwater (30 ppt) immediately upon commencing their migration from Chilko Lake. Transportation of smolts downstream generally increased survival to the farthest marine array. The act of tagging may have affected smolts in the marine environment in some years as dummy-tagged fish had poorer survival than control fish in saltwater laboratory-based experiments. Current fisheries models for forecasting the number of adult sockeye returning to spawn have been inaccurate in recent years and generally do not incorporate juvenile or smolt survival information. Our results highlight significant potential for early migration conditions to influence adult recruitment. This article is protected by copyright. All rights reserved.

Description: When possible, many species will shift in elevation or latitude in response to rising temperatures. However, before such shifts occur, individuals will first tolerate environmental change and then modify their behavior to maintain heat balance. Behavioral thermoregulation allows animals a range of climatic tolerances and makes predicting geographic responses under future warming scenarios challenging. Because behavioral modification may reduce an individual's fecundity by, for example, limiting foraging time and thus caloric intake, we must consider the range of behavioral options available for thermoregulation to accurately predict climate change impacts on individual species. To date, few studies have identified mechanistic links between an organism's daily activities and the need to thermoregulate. We used a biophysical model, Niche Mapper, to mechanistically model microclimate conditions and thermoregulatory behavior for a temperature-sensitive mammal, the American pika ( Ochotona princeps ). Niche Mapper accurately simulated microclimate conditions, as well as empirical metabolic chamber data for a range of fur properties, animal sizes, and environmental parameters. Niche Mapper predicted pikas would be behaviorally constrained because of the need to thermoregulate during the hottest times of the day. We also showed that pikas at low elevations could receive energetic benefits by being smaller in size and maintaining summer pelage during longer stretches of the active season under a future warming scenario. We observed pika behavior for 288 h in Glacier National Park, Montana, and thermally characterized their rocky, montane environment. We found that pikas were most active when temperatures were cooler, and at sites characterized by high elevations and north-facing slopes. Pikas became significantly less active across a suite of behaviors in the field when temperatures surpassed 20°C, which supported a metabolic threshold predicted by Niche Mapper. In general, mechanistic predictions and empirical observations were congruent. This research is unique in providing both an empirical and mechanistic description of the effects of temperature on a mammalian sentinel of climate change, the American pika. Our results suggest that previously underinvestigated characteristics, specifically fur properties and body size, may play critical roles in pika populations' response to climate change. We also demonstrate the potential importance of considering behavioral thermoregulation and microclimate variability when predicting animal responses to climate change. We built a mechanistic model, focusing on thermoregulation, for a climate change sentinel, the American pika, and tested it against 288 h of field observations. We observed and the model predicted heat stress when ambient temperatures at animal height were above 20°C. We predict that future climate warming may place enhanced selective pressure on factors important for pika thermoregulation, specifically body size and molt-timing.