Kremen Claire, Williams Neal M, Thorp Robbin W
Department of Ecology and Evolutionary Biology, Guyot Hall, Princeton University, Princeton, NJ 08544, USA.
Proc Natl Acad Sci U S A. 2002 Dec 24;99(26):16812-6. doi: 10.1073/pnas.262413599. Epub 2002 Dec 16.
Ecosystem services are critical to human survival; in selected cases, maintaining these services provides a powerful argument for conserving biodiversity. Yet, the ecological and economic underpinnings of most services are poorly understood, impeding their conservation and management. For centuries, farmers have imported colonies of European honey bees (Apis mellifera) to fields and orchards for pollination services. These colonies are becoming increasingly scarce, however, because of diseases, pesticides, and other impacts. Native bee communities also provide pollination services, but the amount they provide and how this varies with land management practices are unknown. Here, we document the individual species and aggregate community contributions of native bees to crop pollination, on farms that varied both in their proximity to natural habitat and management type (organic versus conventional). On organic farms near natural habitat, we found that native bee communities could provide full pollination services even for a crop with heavy pollination requirements (e.g., watermelon, Citrullus lanatus), without the intervention of managed honey bees. All other farms, however, experienced greatly reduced diversity and abundance of native bees, resulting in insufficient pollination services from native bees alone. We found that diversity was essential for sustaining the service, because of year-to-year variation in community composition. Continued degradation of the agro-natural landscape will destroy this "free" service, but conservation and restoration of bee habitat are potentially viable economic alternatives for reducing dependence on managed honey bees.
生态系统服务对人类生存至关重要；在某些特定情况下，维持这些服务为保护生物多样性提供了有力论据。然而，大多数服务的生态和经济基础却鲜为人知，这阻碍了对它们的保护和管理。几个世纪以来，农民们将欧洲蜜蜂（西方蜜蜂）群落引入田间和果园以提供授粉服务。然而，由于疾病、杀虫剂及其他影响，这些蜂群正变得越来越稀少。本地蜜蜂群落也提供授粉服务，但其提供的授粉量以及这如何随土地管理方式而变化尚不清楚。在此，我们记录了在距离自然栖息地远近及管理类型（有机与传统）各异的农场中，本地蜜蜂对作物授粉的单个物种及总体群落贡献。在靠近自然栖息地的有机农场，我们发现本地蜜蜂群落即使在没有人工饲养蜜蜂干预的情况下，也能为授粉需求大的作物（如西瓜）提供充分的授粉服务。然而，所有其他农场的本地蜜蜂多样性和数量都大幅减少，仅靠本地蜜蜂无法提供足够的授粉服务。我们发现，由于群落组成的逐年变化，多样性对于维持授粉服务至关重要。农业 - 自然景观的持续退化将破坏这种“免费”服务，但保护和恢复蜜蜂栖息地可能是减少对人工饲养蜜蜂依赖的可行经济替代方案。
