Towards a general theory of ecological impacts of multiple, simultaneous stressors.

预测自然和人为压力因素对生态群落的影响是生态学研究的重要课题之一。气候变化和栖息地的破碎化被认为是对全球环境的两大威胁。预计它们将影响支撑生态系统服务的群落的多样性、组成和动态。污染和（过度）开采自然资源使这些影响变得相当复杂。可以肯定的是，社区正在同时经历多重挑战。人们似乎也很容易认为，综合起来的威胁可能会产生影响。压力源越多，影响就越大、越严重。然而，可能是由于生物学的工作方式，一些压力源相互抵消，或者结合起来的影响比预期的要小。当然，相反的情况也是可能的（而且是可怕的）：压力源可能会相互加剧，导致的影响比仅仅把它们的影响加在一起要糟糕得多。不幸的是，我们真的不知道压力是否以加性或非加性的方式结合。我们对在多重压力下，种群动态、群落结构和生态系统功能之间的反馈是如何运作的，有非常初步的了解。我们认为，事实上，这些累加效应或互动效应的分布可以告诉我们，压力源的影响有多可预测，又有多普遍。我们建议通过建立一个模型来探索由多种压力源引起的附加和交互效应的分布，该模型允许生物学来确定压力是否加在一起，然后将其与实际数据中的模式进行比较。我们的独特贡献来自于认识到某些压力，比如温度，会对生理产生作用，并改变新陈代谢、生长和繁殖等事情发生的速度。相比之下，一些压力源只是通过收获或污染等直接影响来杀死事物。我们将建立第一个能够容纳这些差异的模型，使我们有最好的机会了解压力源如何结合起来影响人口、社区结构和我们所依赖的生态系统功能。

Predicting the impact that combined natural and anthropogenic stressors have on ecological communities ranks as one of the most important research agendas in ecology. Climate change and the fragmentation of habitat are considered the two largest threats to the global environment. They are expected to impact on the diversity, composition and dynamics of the communities that underpin ecosystem services. Pollution and (over)harvesting of natural resources considerably complicate these impacts. It is safe to assume that communities are experiencing multiple, simultaneous challenges.It also seems easy to assume that combined threats might simply add up to generate impact. The more stressors, the more and worse the impact. However, it may be that, because of the way biology works, some stressors cancel each other out, or combine to be less impactful than expected. And, of course, the opposite is possible (and scary): stressors may exacerbate each other, leading to effects that are worse than expected compared to just adding their effects together.Unfortunately, we really have no idea about whether stress combines in an additive or non-additive fashion. And we have very rudimentary understanding of how feedbacks among population dynamics, community structure and ecosystem function operate under multiple stressors. We suggest, in fact, that the distribution of these additive or interactive effects can tell us something about how predictable and how generalizable are the effects of stressors.We propose to explore the distribution of additive and interactive effects caused by multiple stressors by building a model that allows biology to determine if stress adds up or not, and then comparing this to patterns in real data. Our unique contribution comes from recognising that some kinds of stress, like temperature, act on physiology and change the rates at which things like metabolism growth and reproduction happen. In contrast, some stressors simply kill things, either by harvesting or by direct impacts from things like pollution. We will build the first model that allows these distinctions to be accommodated, giving us the best chance of understanding how stressors combine to affect populations, the structure of communities and the ecosystem functions we rely upon.