Earth to Ocean Research Group, Simon Fraser University, Burnaby, BC, Canada.
School of Aquatic and Fishery Sciences, University of Washington, Seattle, WA, USA.
Glob Chang Biol. 2017 May;23(5):1871-1880. doi: 10.1111/gcb.13536. Epub 2016 Dec 18.
Integrating knowledge of environmental degradation, biodiversity change, and ecosystem processes across large spatial scales remains a key challenge to illuminating the resilience of earth's systems. There is now a growing realization that the manner in which communities will respond to anthropogenic impacts will ultimately control the ecosystem consequences. Here, we examine the response of freshwater fishes and their nutrient excretion - a key ecosystem process that can control aquatic productivity - to human land development across the contiguous United States. By linking a continental-scale dataset of 533 fish species from 8100 stream locations with species functional traits, nutrient excretion, and land remote sensing, we present four key findings. First, we provide the first geographic footprint of nutrient excretion by freshwater fishes across the United States and reveal distinct local- and continental-scale heterogeneity in community excretion rates. Second, fish species exhibited substantial response diversity in their sensitivity to land development; for native species, the more tolerant species were also the species contributing greater ecosystem function in terms of nutrient excretion. Third, by modeling increased land-use change and resultant shifts in fish community composition, land development is estimated to decrease fish nutrient excretion in the majority (63%) of ecoregions. Fourth, the loss of nutrient excretion would be 28% greater if biodiversity loss was random or 84% greater if there were no nonnative species. Thus, ecosystem processes are sensitive to increased anthropogenic degradation but biotic communities provide multiple pathways for resistance and this resistance varies across space.
将环境退化、生物多样性变化和生态系统过程的知识整合到较大的空间尺度仍然是阐明地球系统弹性的关键挑战。现在越来越认识到，社区对人为影响的反应方式最终将控制生态系统的后果。在这里，我们研究了淡水鱼类及其营养排泄（一种可以控制水生生产力的关键生态系统过程）对美国大陆各地人类土地开发的反应。通过将来自 8100 个溪流位置的 533 种鱼类的大陆尺度数据集与物种功能特征、营养排泄和土地遥感相关联，我们提出了四个关键发现。首先，我们提供了美国淡水鱼类营养排泄的第一个地理足迹，并揭示了社区排泄率在局部和大陆尺度上的明显异质性。其次，鱼类物种在对土地开发的敏感性方面表现出显著的响应多样性；对于本地物种，更具耐受性的物种也是在营养排泄方面对生态系统功能贡献更大的物种。第三，通过模拟土地利用变化的增加和由此导致的鱼类群落组成的变化，估计土地开发将使大多数（63%）生态区的鱼类营养排泄减少。第四，如果生物多样性的丧失是随机的，那么营养排泄的损失将增加 28%；如果没有外来物种，那么营养排泄的损失将增加 84%。因此，生态系统过程对人为退化很敏感，但生物群落提供了多种抵抗途径，这种抵抗途径在空间上有所不同。
