Recent decades have witnessed substantial changes in freshwater biodiversity worldwide. Although research has shown that freshwater biodiversity can be shaped by changes in habitat diversity and human‐induced pressure, the potentials for interaction between these drivers and freshwater biodiversity at large spatial extents remain unclear. To address these issues, we employed a spatially extensive multitrophic fish and insect database from 3323 stream sites across the United States, to investigate the ability of habitat diversity to modulate the effect of human pressure on the richness and abundance of fish and insects. We found evidence that high levels of habitat diversity were associated with increased richness and abundance of fish and insects (including whole‐assemblage and individual trophic guilds). We also show that the effects of human pressure on the richness and abundance of fish and insects tend to become positive at high levels of habitat diversity. Where habitat diversity is low, human pressure strongly reduces insect richness and abundance, whereas these reductions are attenuated at high levels of habitat diversity. Structural equation modeling revealed that human pressure reduced habitat diversity, indirectly negatively affecting the richness and abundance of fish and insects. These findings illustrate that, in addition to promoting greater fish and insect biodiversity, habitat diversity may mitigate the deleterious effects of human pressures on these two stream assemblages. Overall, our study suggests that maintaining high levels of habitat diversity is a useful way to protect freshwater biodiversity from ongoing increases in human pressure. However, if human pressures continue to increase, this will reduce habitat diversity, further threatening stream assemblages.

中文翻译：

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栖息地多样性减轻了人类压力对河流生物多样性的影响


近几十年来，全球淡水生物多样性发生了重大变化。尽管研究表明，淡水生物多样性可以受到栖息地多样性变化和人为压力的影响，但这些驱动因素与淡水生物多样性在大空间范围内相互作用的可能性仍不清楚。为了解决这些问题，我们采用了来自美国 3323 个溪流地点的空间广泛的多营养鱼类和昆虫数据库，以研究栖息地多样性调节人类压力对鱼类和昆虫的丰富性和丰度的影响的能力。我们发现证据表明，高水平的栖息地多样性与鱼类和昆虫（包括整个组合和单个营养公会）的丰富度和丰度增加有关。我们还表明，在高水平的栖息地多样性下，人类压力对鱼类和昆虫的丰富度和丰度的影响往往会变得积极。在栖息地多样性较低的地方，人类压力会大大降低昆虫的丰富度和丰度，而这些减少会在栖息地多样性水平较高时减弱。结构方程模型显示，人类压力降低了栖息地的多样性，间接对鱼类和昆虫的丰富性和丰度产生了负面影响。这些发现表明，除了促进更大的鱼类和昆虫生物多样性外，栖息地多样性还可以减轻人类压力对这两个溪流组合的有害影响。总体而言，我们的研究表明，保持高水平的栖息地多样性是保护淡水生物多样性免受持续增加的人类压力的有用方法。 然而，如果人类压力继续增加，这将减少栖息地多样性，进一步威胁溪流组合。