Abstract We examined differences in species richness between reference and impacted sites to illustrate the extent to which estimated impacts of land-use change on biodiversity can be affected by the degree of baseline suitability (intactness of reference sites) and the species assemblage under consideration. We mist-netted birds at five continuous Amazonian forest sites and 33 land-bridge forest islands (0.63–1699 ha) within a large hydroelectric reservoir. We then produced a gradient of baseline suitability based on forest area of five sets of reference sites, namely continuous forest, 1000 ha, 500 ha, 250 ha and 100 ha, and contrasted these with all smaller islands combined considering two types of species assemblages. The first comprised only species captured at reference sites (baseline species assemblage), whereas the second comprised all species captured at all sites (overall species assemblage). We also examined biodiversity complementarity to define the minimum set of forest islands retaining the most number of species occurring both at continuous forest sites and across all sites. A focus on the baseline species assemblage from the most suitable baseline (continuous forest) resulted in an estimated decrease of 67% in species richness at impacted sites. In contrast, a focus on the overall species assemblage along with the use of the least suitable baseline (100 ha) as a reference condition reversed this trend, resulting in an estimated increase of 43% in species richness at impacted sites. We therefore underline the imperative of considering the intactness of reference sites to accurately assess the impacts of land-use change on biodiversity and establish conservation strategies.

中文翻译：

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基线适宜性在评估土地利用变化对生物多样性的影响中的作用

摘要 我们检查了参考地点和受影响地点之间物种丰富度的差异，以说明土地利用变化对生物多样性的估计影响在多大程度上受基线适宜性程度（参考地点的完整性）和所考虑的物种组合的影响。我们在一个大型水力发电库内的五个连续的亚马逊森林地点和 33 个陆桥森林岛屿（0.63-1699 公顷）用雾网捕鸟。然后，我们根据五组参考地点的森林面积，即连续森林、1000 公顷、500 公顷、250 公顷和 100 公顷，产生了基线适宜性梯度，并将这些与考虑两种物种组合的所有较小岛屿进行对比。第一个仅包括在参考地点捕获的物种（基线物种组合），而第二个包括在所有地点捕获的所有物种（整体物种组合）。我们还研究了生物多样性的互补性，以定义保留在连续森林地点和所有地点发生的最多物种的最小森林岛屿集。关注最合适基线（连续森林）的基线物种组合导致受影响地点的物种丰富度估计下降了 67%。相比之下，关注整体物种组合以及使用最不合适的基线（100 公顷）作为参考条件扭转了这一趋势，导致受影响地点的物种丰富度估计增加了 43%。