Anthropogenic habitat destruction leads to habitat loss and fragmentation, both of which interact to determine how biodiversity changes at the landscape level. While the detrimental effects of habitat loss are clear, there is a long-standing debate about the role of habitat fragmentation per se. We identify the influence of the total habitat amount lost as a modulator of the relationship between habitat fragmentation and biodiversity. Using a simple metacommunity model characterized by colonization–competition (C–C) trade-offs, we show that the magnitude of habitat loss can induce a unimodal response of biodiversity to habitat fragmentation. When habitat loss is low, habitat fragmentation promotes coexistence by suppressing competitively dominant species, while habitat fragmentation at high levels of habitat loss can shape many smaller isolated patches that drive extinctions of superior competitors. While the C–C trade-off is not the only mechanism for biodiversity maintenance, the modulation of habitat fragmentation effects by habitat loss is probably common. Reanalysis of a globally distributed dataset of fragmented animal and plant metacommunities shows an overall pattern that supports this hypothesis, suggesting a resolution to the debate regarding the relative importance of positive versus negative fragmentation effects.

人为栖息地破坏导致栖息地丧失和破碎，两者相互作用，决定了景观层面生物多样性的变化。虽然栖息地丧失的不利影响是显而易见的，但关于栖息地破碎化本身的作用存在长期争论。我们确定了栖息地总损失量作为栖息地破碎化与生物多样性之间关系的调节因素的影响。使用以殖民-竞争（C-C）权衡为特征的简单元群落模型，我们表明栖息地丧失的程度可以引起生物多样性对栖息地破碎化的单峰反应。当栖息地丧失程度较低时，栖息地破碎化会通过抑制竞争优势物种来促进共存，而栖息地破碎化程度较高时，会形成许多较小的孤立斑块，从而导致优势竞争者的灭绝。虽然 C-C 权衡并不是生物多样性维持的唯一机制，但栖息地丧失对栖息地破碎化效应的调节可能很常见。对全球分布的动植物元群落碎片数据集的重新分析显示了支持这一假设的总体模式，这为关于正碎片化效应与负碎片化效应的相对重要性的争论提供了解决方案。