Tennenbaum Marine Observatories Network, Smithsonian Institution, Washington, District of Columbia, 20013, USA.
Smithsonian Environmental Research Center, Edgewater, Maryland, 21037, USA.
Ecology. 2019 Apr;100(4):e02617. doi: 10.1002/ecy.2617.
Marine protected areas (MPAs) have grown exponentially, emerging as a widespread tool to conserve biodiversity and enhance fisheries production. Although numerous empirical studies and global syntheses have evaluated the effects of MPAs on community structure (e.g., biodiversity), no broad assessment concerning their capacity to influence ecological processes (e.g., species interactions) exists. Here, we present meta-analyses that compare rates of predation and herbivory on a combined 32 species across 30 MPAs spanning 85° of latitude. Our analyses synthesize the fate of 15,225 field experiment assays, and demonstrate that MPAs greatly increased predation intensity on animals but not herbivory on macroalgae or seagrass. Predation risk, quantified as the odds of prey being eaten, was largely determined by predator abundance and biomass within reserves. At MPAs with the greatest predator accumulation, the odds of predation increased to nearly 49:1, as opposed to 1:1 at MPAs where predators actually declined. Surprisingly, we also found evidence that predation risk declined with increased sea-surface temperature. Greater predation risk within MPAs was consistent with predator and prey population abundance estimates, where predators increased 4.4-fold within MPAs, whereas prey decreased 2.2-fold. For herbivory, the lack of change may have been driven by functional redundancy and the inability of reserves to increase herbivore abundance relative to fished zones in our sample. Overall, this work highlights the capacity of MPAs to restore a critical ecosystem function such as predation, which mediates energy flows and community assembly within natural systems. However, our review of the literature also uncovers relatively few studies that have quantified the effects of MPAs on ecosystem function, highlighting a key gap in our understanding of how protected areas may alter ecological processes and deliver ecosystem services. From a historical perspective, these findings suggest that modern levels of predation in the coastal oceans may currently only be a fraction of the baseline prior to human exploitation.
海洋保护区（MPAs）的数量呈指数级增长，已成为保护生物多样性和提高渔业产量的广泛工具。尽管许多实证研究和全球综合评估已经评估了 MPAs 对群落结构（如生物多样性）的影响，但对于它们影响生态过程（如物种相互作用）的能力，尚无广泛的评估。在这里，我们进行了荟萃分析，比较了横跨 85 个纬度的 30 个 MPAs 中 32 个物种的捕食和食草率。我们的分析综合了 15225 个野外实验测定的结果，结果表明，MPAs 大大增加了动物的捕食强度，但对大型藻类或海草的食草作用没有影响。捕食风险（以猎物被吃掉的可能性来衡量）主要取决于保护区内的捕食者数量和生物量。在捕食者积累最多的 MPAs 中，捕食的可能性增加到近 49:1，而在捕食者实际上减少的 MPAs 中，捕食的可能性为 1:1。令人惊讶的是，我们还发现捕食风险随着海水表面温度的升高而降低的证据。在 MPAs 中，捕食风险增加的原因可能是捕食者和猎物种群数量的增加，在 MPAs 中，捕食者的数量增加了 4.4 倍，而猎物的数量减少了 2.2 倍。对于食草作用，缺乏变化可能是由于功能冗余以及保护区相对于我们样本中的捕鱼区无法增加食草动物的数量所致。总体而言，这项工作强调了 MPAs 恢复捕食等关键生态系统功能的能力，捕食作用调节着自然系统中的能量流动和群落组装。然而，我们对文献的回顾也发现，只有相对较少的研究量化了 MPAs 对生态系统功能的影响，这突显了我们对保护区如何改变生态过程和提供生态系统服务的理解存在一个关键的差距。从历史上看，这些发现表明，目前沿海海洋中的捕食水平可能只是人类开发之前的基线的一小部分。
