Cropland expansion outweighs the monetary effect of declining natural vegetation on ecosystem services in sub-Saharan Africa
Cropland expansion outweighs the monetary effect of declining natural vegetation on ecosystem services in sub-Saharan Africa
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DOI：
10.1016/j.ecoser.2020.101154
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发表时间：
2020-10-01
影响因子：
7.6
通讯作者：
Sun, Jian
中科院分区：
文献类型：
--
作者：
Fenta, Ayele Almaw;Tsunekawa, Atsushi;Sun, Jian
土地覆被和土地退化的变化改变了自然生态系统，从而影响到这些生态系统提供的服务。然而，很少有人试图在大的空间尺度上和在人类活动的强烈影响下估计土地覆被变化和土地退化对生态系统服务的影响。在这里，我们使用欧洲航天局气候变化倡议土地覆盖图（1992-2015）和价值转移估值方法来估计生态系统服务价值（ESV）的变化，以应对撒哈拉以南非洲（SSA）的土地覆盖变化。此外，我们估计由于土地退化的ESV的损失，通过使用长期（1992-2015年）的趋势，在年度归一化差异植被指数作为长期生物量生产力下降的代理。我们的研究结果显示，在1992年至2015年期间，耕地增加了约2000万公顷，主要是以森林和灌木丛为代价。据估计，撒哈拉以南非洲的总ESV约为9万亿美元/年（-1），其中55%来自农田和落叶林，贡献相当。土地覆被变化导致总ESV净增加1250亿美元（-1）（1992-2015年），尽管由于万年青林和灌木林的转换，ESV损失了600亿美元。总的来说，耕地扩张占总ESV（1250亿美元）增长的60%左右，从而超过了由于自然植被减少而导致的ESV下降。土地退化热点覆盖了约5%的撒哈拉以南非洲地区，导致ESV总损失约560亿美元（-1），其中近65%是由于森林和农田的退化。环境承载力的变化因次区域、气候带和国家而异，取决于主要的土地覆被变化和土地退化的程度。我们的研究结果为生态系统的可持续利用和管理提供了有用的见解。
Changes in land cover and land degradation alter natural ecosystems, thereby affecting the services these ecosystems provide. However, there have been few attempts to estimate the effects of land cover change and land degradation on ecosystem services at large spatial scales and under the strong influence of human activities. Here, we used the European Space Agency Climate Change Initiative land cover maps (1992-2015) and the value transfer valuation method to estimate the changes in ecosystem services value (ESV) in response to land cover change in sub-Saharan Africa (SSA). Moreover, we estimated the loss of ESV due to land degradation by using the long-term (1992-2015) trend in the annual normalized difference vegetation index as a proxy for longterm biomass productivity decline. Our results revealed that, between 1992 and 2015, cropland increased by about 20 million ha, largely at the expense of forest and shrubland. The total estimated ESV of SSA was about US $9 trillion year(-1), of which 55% was derived from cropland and deciduous forest, with comparable contributions. Land cover change resulted in a net increase in the total ESV by US$125 billion year(-1) (1992-2015), albeit with an ESV loss of US$60 billion year -1 from the conversion of evergreen forest and shrubland. Overall, cropland expansion accounted for about 60% of the increase in the total ESV (US$125 billion year(-1)), thereby outweighing the decrease in ESV due to the decline in natural vegetation. Land degradation hotspots covered about 5% of SSA, resulting in a total ESV loss of about US$56 billion year(-1), of which nearly 65% was due to the degradation of forests and croplands. Changes in ESV varied across sub-regions, climate zones, and countries, depending on the dominant land cover change and the extent of land degradation. Our results provide useful insights for making informed decisions towards sustainable use and management of ecosystems.