Coupling the population dynamics and ecosystem function of grazing fishes

社会在道德和法律上都有责任对生物多样性进行可持续管理。大多数保护策略要么集中于一个特别重要的物种，并假设保护措施也保护生态系统的其他组成部分，要么试图通过在保护区中留出一些栖息地来保护许多物种。后一种方法假定许多物种可以在受保护的地区完成它们的生命周期。另一种范式，尽管很难实现，是管理者关注驱动生态系统的关键过程。如果生态系统过程保持完整，那么生物多样性的许多组成部分应该是可持续的。迄今为止，尽管大多数政府现在在法律上有义务采取的“基于生态系统的管理方法”明确体现了这种方法，但这种方法的示范很少。基于过程的保护方法只有在满足两个条件时才有效。首先，生物多样性受到数量有限的过程的深刻影响，其次，这些过程受到管理干预。西大西洋的珊瑚礁为这种方法提供了一个非常令人信服的案例。珊瑚从干扰中恢复的能力高度依赖于其竞争对手海藻的丰富程度。反过来，海藻的可用性取决于吃草的鹦嘴鱼。不充分的放牧会导致海藻大量繁殖，并阻止珊瑚建立生物多样性所依赖的复杂珊瑚礁栖息地。这个项目建立在早期NERC拨款的成功基础上，使我们能够明确地管理一个关键的生态系统过程（鹦嘴鱼放牧）。我们最近模拟了放牧在珊瑚礁动态中的重要性。该模型允许珊瑚与海藻竞争，生态系统受到包括飓风在内的严重外部影响。人们发现，鹦嘴鱼的放牧对珊瑚的动态产生了压倒性的积极影响。然而，虽然我们现在认识到维持放牧的重要性，但我们缺乏实现这一目标的科学。该项目通过模拟鹦嘴鱼的种群动态和开发对其社区的影响来填补这一空白。这些模型有两种用途。首先，它们将允许我们测试关于被剥削社区的新的生态假设。其次，我们将把鹦嘴鱼种群动态模型与现有的鹦嘴鱼放牧模型和放牧对珊瑚礁动态的影响模型耦合起来。因此，我们的耦合模型使我们能够发展基于生态系统的管理理论，因为我们可以回答这个问题，“如何可持续地管理鹦嘴鱼群落，使采掘活动不会减少放牧超过生态系统所需的水平？”该项目的成果将引起广泛的兴趣，因为我们将显著发展“基于生态系统的管理”背后的科学，并通过耦合复杂的生态模型，为复杂系统的分析提供新的见解（这位于生物学和数学的交叉点）。

Societies are ethically and legally charged with the sustainable management of biodiversity. Most conservation strategies either focus on a particularly important species and assume that the conservation measures also protect other components of the ecosystem or attempt to protect many species by setting aside some of their habitat in reserves. The latter approach assumes that many species can complete their life cycle in the area preserved. An alternative paradigm, albeit one that has been difficult to realize, is that managers focus on the key processes driving the ecosystem. If the ecosystem processes remain intact, then many components of biodiversity should be sustainable. To date, there have been few demonstrations of this approach even though it is explicitly embodied by an 'Ecosystem-based approach to management' to which most governments are now legally obliged to undertake. A process-based approach to conservation will only work if two conditions are met. Firstly, that biodiversity is profoundly influenced by a limited number of processes and secondly that these processes are subject to management intervention. Coral reefs of the Western Atlantic provide an exceptionally compelling case for this approach. The ability of corals to recover from disturbance is highly dependent on the abundance of their seaweed competitor. In turn, the availability of seaweed is determined by grazing parrotfish. Inadequate levels of grazing allow seaweed to bloom and prevents corals from building the complex reef habitat on which much biodiversity depends. This project builds on the success of an earlier NERC grant and enables us to manage a key ecosystem process (parrotfish grazing) explicitly. We recently modelled the importance of grazing in coral reef dynamics. The model allowed corals to compete with seaweeds and the ecosystem was subjected to severe external impacts including hurricanes. Parrotfish grazing was found to exert an overwhelming positive impact on the dynamics of corals. However, whilst we now appreciate the importance of maintaining grazing, we lack the science to achieve it. This project fills this gap by modelling the population dynamics of parrotfish and the impact of exploitation on their communities. The models have two uses. Firstly, they will allow us to test novel ecological hypotheses about exploited communities. Secondly, we will couple the model of parrotfish population dynamics with our existing models of parrotfish grazing and the impact of grazing on coral reef dynamics. Thus, our coupled models allow us to develop the theory of ecosystem-based management because we can answer the question, 'How should parrotfish communities be managed sustainably so that extractive activities do not reduce grazing beyond the level required by the ecosystem?'. Outcomes of this project will have wide interest because we will significantly develop the science behind 'ecosystem-based management' and, by coupling complex ecological models, provide fresh insight into the analysis of complex systems (which lies at the intersection of biology and mathematics).