Ecosystem engineers are organisms that affect ecosystem state by modifying the physical habitats in which biological interactions occur. Such engineering effect depends on both the engineers for environmental transformation and the persistency of engineered structures, but the distinction has rarely been considered. Here, we examined their relative effect on ecosystem in terms of ecological resilience. We used a mathematical model of a coral reef that incorporates reciprocal facilitation between corals and herbivores. Coral skeletons create physical habitats and promote habitat complexity, allowing more herbivore grazing on macroalgae, which opens further space for coral colonization. By quantifying resilience in form of its basin of attraction, we found that resilience declined much rapidly with the loss of habitat complexity (engineered structures) than from the loss of either corals (engineers) or herbivores, under the substantial pressures of fishing and eutrophication. This model outcome is in accordance with observed empirical patterns. It arises due to two characteristics of habitat complexity: slow temporal changes and habitat provisioning. Habitat complexity can persist even when corals are lost, facilitating the recovery of herbivores and, in turn, of corals. Our model suggests that, as the persistency of engineered structures increases, their influence on ecosystem dynamics increases and becomes independent from that of ecosystem engineer. Identifying such a distinction and its context are vital to preserving ecosystem resilience and to better avoid catastrophic shifts.

中文翻译：

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生态系统工程结构促进生态恢复：珊瑚礁模型

生态系统工程师是通过修改发生生物相互作用的物理栖息地来影响生态系统状态的生物。这种工程效果取决于工程师进行环境改造和工程结构的持久性，但是很少考虑到这种区别。在这里，我们从生态弹性的角度考察了它们对生态系统的相对影响。我们使用了珊瑚礁的数学模型，该模型结合了珊瑚和食草动物之间的相互促进作用。珊瑚骨骼创造了物理栖息地，并加剧了栖息地的复杂性，使大型草食动物得以放牧，从而为珊瑚定殖提供了更多空间。通过以吸引盆的形式量化弹性，我们发现，在捕鱼和富营养化的巨大压力下，栖息地复杂性（工程结构）的丧失所带来的抵御能力下降比珊瑚（工程人员）或草食动物的丧失所造成的抵抗力下降要快得多。该模型结果与观察到的经验模式一致。它的产生是由于栖息地复杂性的两个特征：缓慢的时间变化和栖息地供应。即使失去了珊瑚，栖息地的复杂性也可能持续存在，从而促进了草食动物和珊瑚的恢复。我们的模型表明，随着工程结构的持久性增加，它们对生态系统动力学的影响也增加，并且变得独立于生态系统工程师。确定这种区别及其背景对于保持生态系统的弹性并更好地避免灾难性变化至关重要。