Publication Date:
2016-10-13
Description:
Increases in woody plant cover in savanna-grassland environments have been reported on globally for over 50 years and are generally perceived as a threat to rangeland productivity and biodiversity. Despite this few attempts have been made to estimate the extent of woodland increase at a national scale, principally due to technical constraints such as availability of appropriate remote sensing products. In this study we aim to measure the extent to which woodlands have replaced grasslands in South Africa's grassy biomes. We use multi-season Landsat data in conjunction with satellite L-band radar backscatter data to estimate the extent of woodlands and grasslands in 1990 and 2013. The method employed allows for a unique, nation-wide measurement of transitions between grassland and woodland classes in recent decades. We estimate that during the 23 year study period woodlands have replaced grasslands over ~57 000 km 2 and conversely that grassland have replaced woodlands over ~30 000 km 2 ; a net increase in the extent of woodland of ~27 000 km 2 and an annual increase of 0.22%. The changes varied markedly across the country; areas receiving over 500 mm mean annual precipitation showed higher rates of woodland expansion than regions receiving less than 500 mm (0.31% y -1 & 0.11% y -1 respectively). Protected areas with elephants showed clear loss of woodlands (-0.43% y -1 ) while commercial rangelands and traditional rangelands showed increases in woodland extent (〉0.19% y -1 ). The woodland change map presented here provides a unique opportunity to test the numerous models of woody plant encroachment at a national / regional scale. This article is protected by copyright. All rights reserved.
Print ISSN:
1354-1013
Electronic ISSN:
1365-2486
Topics:
Biology
,
Energy, Environment Protection, Nuclear Power Engineering
,
Geography
Permalink
