Coupling the population dynamics and ecosystem function of grazing fishes

社会在道德上和法律上都有责任对生物多样性进行可持续管理。大多数保护战略要么把重点放在一个特别重要的物种上，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留出一些栖息地来保护许多物种。后一种方法假设许多物种可以在被保护的区域完成它们的生命周期。另一种范式是，管理者专注于推动生态系统的关键过程，尽管这种范式很难实现。如果生态系统过程保持完好，那么生物多样性的许多组成部分应该是可持续的。到目前为止，这种方法很少有示范，尽管它明确体现为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”。只有在满足两个条件的情况下，基于过程的保护方法才会奏效。首先，生物多样性受到有限数量的进程的深刻影响，其次，这些进程受到管理干预。西大西洋的珊瑚礁为这一做法提供了一个特别令人信服的案例。珊瑚从干扰中恢复的能力高度依赖于它们的竞争对手海藻的丰富程度。反过来，海藻的可获得性取决于吃鹦鹉鱼。不充分的放牧水平使海藻大量繁殖，并阻止珊瑚建造许多生物多样性所依赖的复杂的珊瑚礁栖息地。这个项目建立在早期NERC赠款的成功基础上，使我们能够明确地管理一个关键的生态系统过程(鹦鹉放牧)。我们最近对放牧在珊瑚礁动力学中的重要性进行了建模。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。研究发现，鹦鹉放牧对珊瑚的动态产生了压倒性的积极影响。然而，尽管我们现在意识到保持放牧的重要性，但我们缺乏实现这一目标的科学。该项目通过模拟鹦鹉鱼的种群动态和开发对其群落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说。其次，我们将把鹦鹉鱼种群动态模型与我们现有的鹦鹉鱼放牧模型以及放牧对珊瑚礁动态的影响相结合。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样一个问题，‘鹦鹉鱼群落应该如何可持续地管理，以便采掘活动不会减少超过生态系统所要求的水平的放牧？’这个项目的成果将引起广泛的兴趣，因为我们将大力发展“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(位于生物学和数学的交叉点)的分析提供新的见解。

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).