Changing Patterns of Tree Cover in a Tropical Highland Region and Implications for Food, Energy, and Water Resources
Changing Patterns of Tree Cover in a Tropical Highland Region and Implications for Food, Energy, and Water Resources
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热带高地地区树木覆盖模式的变化及其对粮食、能源和水资源的影响
DOI：
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发表时间：
2019
影响因子：
4.6
通讯作者：
A. Ambelu
中科院分区：
文献类型：
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作者：
T. Alemneh;B. Zaitchik;B. Simane;A. Ambelu
摘要埃塞俄比亚的青尼罗河高地是一个人口稠密的农村地区，主要是小农农作物-牲畜混合农业系统。人口增长加上生产力低下，长期以来一直对该区域的自然森林生态系统构成威胁，因为树木被砍伐用作燃料木材，并为放牧或作物生产清理土地。然而，近年来出现了用桉树种植园取代农田的趋势。这种变化对该地区的水文、土壤和农业经济产生了重大影响。本研究考察了青尼罗河高地中心高地地区树木覆盖的变化。1986-2017年的陆地卫星图像被用来描述随时间和空间变化的树木覆盖模式。我们发现，在过去的30年里，这个高原地区的树木总覆盖率发生了巨大的变化。1987年至1999年期间，树木覆盖率急剧下降，特别是在高海拔和低海拔的自然植被地区。这一时期恰逢德尔格政府倒台和向现行政治制度过渡。自1999年以来，树木覆盖率有所增加，近年来增长迅速。这种增长有两种不同的形式：在以前的森林地区重新生长，部分原因是积极的保护措施，以及在中海拔地区建立桉树种植园。这两种类型的树木覆盖的生态和经济影响保护林与林地种植园是相当不同的，与人工林提供生物质能源的粮食生产和水资源的成本。有效监测这些变化对该区域持续制定和执行有效的土地利用政策十分重要。
Abstract The Blue Nile Highlands of Ethiopia are a densely populated, predominantly rural region dominated by smallholder crop-livestock mixed farming systems. Population growth, coupled with low productivity, have long posed a threat to natural forest ecosystems in the region, as trees have been removed for fuel wood and to clear area for grazing or crop production. In recent years, however, there has been a trend to replace cropland with eucalyptus plantations. This change has major implications for the hydrology, soils, and agricultural economy of the region. This study examines changes in tree cover for a highland area at the center of the Blue Nile Highlands. Landsat imagery from 1986-2017 is applied to characterize changing tree cover patterns over space and time. We find that total tree cover in this highland region has shifted dramatically over the past 30 years. Between 1987 and 1999 there was dramatic loss of tree cover, particularly in areas of natural vegetation at high and low elevation. This period coincided with the fall of the Derg government and the transition to the current political system. In the period since 1999 there has been an increase in tree cover, with rapid gains in recent years. This increase has taken two distinct forms: regrowth in previously forested areas, due in part to active conservation measures, and the establishment of eucalyptus plantations in mid-elevation zones. The ecological and economic implications of these two types of tree cover—protected forest vs. woodlot plantations—are quite distinct, with plantation forestry providing biomass energy at a cost to food production and water resources. Effective monitoring of these changes is important for the ongoing development and implementation of effective land use policy in the region.