Department of Ecology and Evolutionary Biology, Princeton University, Guyot Hall, Princeton, NJ, 08544, U.S.A.
Facultad de Biología, Universidad Nacional de la Amazonía Peruana, Iquitos, Perú.
Conserv Biol. 2019 Dec;33(6):1338-1349. doi: 10.1111/cobi.13344. Epub 2019 Aug 1.
Smallholder agriculture is the main driver of deforestation in the western Amazon, where terrestrial biodiversity reaches its global maximum. Understanding the biodiversity value of the resulting mosaics of cultivated and secondary forest is therefore crucial for conservation planning. However, Amazonian communities are organized across multiple forest types that support distinct species assemblages, and little is known about smallholder impacts across the range of forest types that are essential for sustaining biodiversity. We addressed this issue with a large-scale field inventory of birds (point counts) and trees (transects) in primary forest and smallholder agriculture in northern Peru across 3 forest types that are key for Amazonian biodiversity. For birds smallholder agriculture supported species richness comparable to primary forest within each forest type, but biotic homogenization across forest types resulted in substantial losses of biodiversity overall. These overall losses are invisible to studies that focus solely on upland (terra firma) forest. For trees biodiversity losses in upland forests dominated the signal across all habitats combined and homogenization across habitats did not exacerbate biodiversity loss. Proximity to forest strongly predicted the persistence of forest-associated bird and tree species in the smallholder mosaic, and because intact forest is ubiquitous in our study area, our results probably represent a best-case scenario for biodiversity in Amazonian agriculture. Land-use planning inside and outside protected areas should recognize that tropical smallholder agriculture has pervasive biodiversity impacts that are not apparent in typical studies that cover a single forest type. The full range of forest types must be surveyed to accurately assess biodiversity losses, and primary forests must be protected to prevent landscape-scale biodiversity loss.
小农农业是亚马逊西部地区森林砍伐的主要驱动力，那里的陆地生物多样性达到全球最高水平。因此，了解由此产生的耕地和次生林镶嵌体的生物多样性价值对于保护规划至关重要。然而，亚马逊社区分布在多种支持不同物种组合的森林类型中，对于维持生物多样性至关重要的各种森林类型中小农的影响知之甚少。我们通过在秘鲁北部跨越 3 种关键的森林类型对鸟类（点计数）和树木（样带）进行了大规模实地调查来解决这个问题，这些森林类型包括原始森林和小农农业。对于鸟类来说，小农农业在每种森林类型内支持的物种丰富度与原始森林相当，但森林类型之间的生物同质化导致整体生物多样性大量丧失。这些整体损失对于仅关注高地（terra firma）森林的研究是看不见的。对于树木来说，高地森林中的生物多样性损失主导了所有栖息地组合的信号，而栖息地之间的同质化并没有加剧生物多样性的丧失。与森林的接近程度强烈预测了森林相关鸟类和树种在小农镶嵌体中的持续存在，而且由于完整的森林在我们的研究区域中普遍存在，我们的结果可能代表了亚马逊农业中生物多样性的最佳情况。保护区内外的土地利用规划应该认识到，热带小农农业对生物多样性有着普遍的影响，而典型的单一森林类型研究并不能明显体现这些影响。必须对各种森林类型进行全面调查，以准确评估生物多样性的丧失，并且必须保护原始森林，以防止景观尺度的生物多样性丧失。
