Bodin Orjan, Tengö Maria, Norman Anna, Lundberg Jakob, Elmqvist Thomas
Department of Systems Ecology, Stockholm University, 106 91 Stockholm, Sweden.
Ecol Appl. 2006 Apr;16(2):440-51. doi: 10.1890/1051-0761(2006)016[0440:tvossl]2.0.co;2.
Many services generated by forest ecosystems provide essential support for human well-being. However, the vulnerability of these services to environmental change such as forest fragmentation are still poorly understood. We present spatial modeling of the generation of ecosystem services in a human-dominated landscape where forest habitat patches, protected by local taboos, are located in a matrix of cultivated land in southern Madagascar. Two ecosystem services dependent on the forest habitats were addressed: (1) crop pollination services by wild and semidomesticated bees (Apoidea), essential for local crop production of, for example, beans, and (2) seed dispersal services based on the presence of ring-tailed lemurs (Lemur catta). We studied the vulnerability of these ecosystem services to a plausible scenario of successive destruction of the smallest habitat patches. Our results indicate that, in spite of the fragmented nature of the landscape, the fraction of the landscape presently covered by both crop pollination and seed dispersal services is surprisingly high. It seems that the taboo system, though indirectly and unintentionally, contributes to upholding the generation of these services by protecting the forest patches. Both services are, however, predicted to be very vulnerable to the successive removal of small patches. For crop pollination, the rate of decrease in cover was significant even when only the smallest habitat patches were removed. The capacity for seed dispersal across the landscape displayed several thresholds with habitat patch removal. Our results suggest that, in order to maintain capacity for seed dispersal across the landscape and crop pollination cover in southern Androy, the geographical location of the remaining forest patches is more crucial than their size. We argue that in heavily fragmented production landscapes, small forest patches should increasingly be viewed as essential for maintaining ecosystem services, such as agricultural production, and also should be considered in the ongoing process of tripling the area of protected habitats in Madagascar.
森林生态系统产生的许多服务为人类福祉提供了至关重要的支持。然而，这些服务对诸如森林碎片化等环境变化的脆弱性仍未得到充分理解。我们展示了在马达加斯加南部以人类为主导的景观中生态系统服务产生的空间模型，在该景观中，受当地禁忌保护的森林栖息地斑块位于耕地矩阵中。研究了依赖森林栖息地的两种生态系统服务：（1）野生和半驯化蜜蜂（膜翅目）提供的作物授粉服务，这对当地豆类等作物的生产至关重要；（2）基于环尾狐猴（狐猴属）存在的种子传播服务。我们研究了这些生态系统服务在最小栖息地斑块连续遭到破坏这一合理情景下的脆弱性。我们的结果表明，尽管景观具有碎片化的性质，但目前由作物授粉和种子传播服务覆盖的景观比例出奇地高。似乎禁忌系统虽然间接且无意，但通过保护森林斑块有助于维持这些服务的产生。然而，预计这两种服务对小斑块的连续移除都非常脆弱。对于作物授粉，即使仅移除最小的栖息地斑块，覆盖面积的减少率也很显著。景观中种子传播能力随着栖息地斑块的移除呈现出几个阈值。我们的结果表明，为了维持安杜伊南部景观的种子传播能力和作物授粉覆盖面积，剩余森林斑块的地理位置比其大小更为关键。我们认为，在高度碎片化的生产景观中，小森林斑块应越来越被视为维持生态系统服务（如农业生产）的关键要素，并且在马达加斯加将受保护栖息地面积扩大两倍的现行进程中也应予以考虑。
