Department of Systems Ecology, Stockholm University, Stockholm, Sweden.
PLoS One. 2007 May 2;2(5):e402. doi: 10.1371/journal.pone.0000402.
Loss of tropical forests and changes in land-use/land-cover are of growing concern worldwide. Although knowledge exists about the institutional context in which tropical forest loss is embedded, little is known about the role of social institutions in influencing regeneration of tropical forests. In the present study we used Landsat images from southern Madagascar from three different years (1984, 1993 and 2000) and covering 5500 km(2), and made a time-series analysis of three distinct large-scale patterns: 1) loss of forest cover, 2) increased forest cover, and 3) stable forest cover. Institutional characteristics underlying these three patterns were analyzed, testing the hypothesis that forest cover change is a function of strength and enforcement of local social institutions. The results showed a minor decrease of 7% total forest cover in the study area during the whole period 1984-2000, but an overall net increase of 4% during the period 1993-2000. The highest loss of forest cover occurred in a low human population density area with long distances to markets, while a stable forest cover occurred in the area with highest population density and good market access. Analyses of institutions revealed that loss of forest cover occurred mainly in areas characterized by insecure property rights, while areas with well-defined property rights showed either regenerating or stable forest cover. The results thus corroborate our hypothesis. The large-scale spontaneous regeneration dominated by native endemic species appears to be a result of a combination of changes in precipitation, migration and decreased human population and livestock grazing pressure, but under conditions of maintained and well-defined property rights. Our study emphasizes the large capacity of a semi-arid system to spontaneously regenerate, triggered by decreased pressures, but where existing social institutions mitigate other drivers of deforestation and alternative land-use.
热带森林的丧失和土地利用/土地覆盖的变化是全世界日益关注的问题。尽管人们对热带森林丧失所嵌入的制度背景有所了解，但对于社会制度在影响热带森林再生方面的作用却知之甚少。在本研究中，我们使用了来自马达加斯加南部的三个不同年份（1984 年、1993 年和 2000 年）的 Landsat 图像，覆盖面积为 5500 平方公里，并对三个不同的大规模模式进行了时间序列分析：1）森林覆盖的丧失，2）森林覆盖的增加，3）森林覆盖的稳定。分析了这些模式背后的制度特征，检验了森林覆盖变化是地方社会制度的强度和执行情况的函数的假设。结果表明，在整个 1984-2000 年期间，研究区域的总森林覆盖面积减少了 7%，但在 1993-2000 年期间，总森林覆盖面积总体上增加了 4%。森林覆盖损失最大的发生在人口密度低、距离市场较远的地区，而人口密度最高、市场准入条件好的地区则保持了稳定的森林覆盖。制度分析表明，森林覆盖的丧失主要发生在产权不安全的地区，而产权明确的地区则表现出再生或稳定的森林覆盖。结果证实了我们的假设。以本地特有物种为主导的大规模自然再生，似乎是降水变化、移民以及人口和牲畜放牧压力减少的结果，但前提是维持和明确的产权条件。我们的研究强调了半干旱系统在压力减轻的情况下具有很大的自然再生能力，但现有的社会制度减轻了其他森林砍伐驱动因素和替代土地利用的影响。
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