Biodiversity on farms: a complex systems approach

背景：在过去的50年里，耕地农业的集约化与生物多样性的大量损失有关，人们非常担心集约化农业与生物多样性的保护是不相容的。此外，令人不安的是，研究农田鸟类等指标群体并不能提供促进生物多样性所需的信息。我们的目标是为一个有机农场构建一个大型生态网络，展示物种是如何相互联系的，然后使用复杂的系统方法来预测物种损失和物种恢复的影响。为什么要研究这个学科领域？如果生态学家、土地管理者和政策制定者要可持续地管理农田生物多样性，那么他们需要了解物种相互联系的方式。复杂系统理论预测，仅仅几个高度相关物种的灭绝就可能导致一连串的二次灭绝，这可能导致网络的彻底崩溃。简单地说，像农场食物网这样的复杂系统在相当小的灾难面前可能非常脆弱。建议：我们将构建一个农场规模的网络，包括植物、昆虫、鸟类和哺乳动物，以及害虫种类和农民。一旦我们构建了网络，我们预计将在一个网络中连接大约1000个物种，我们将模拟物种灭绝的影响。为此，我们将使用计算机模拟网络中主要物种的损失（通过一个接一个地从网络中移除物种），并根据随后的二次灭绝的数量和范围来衡量网络的稳健性。非常少量的初级灭绝可以引起营养级联。例如，在154个物种网络中，模拟10%的物种损失足以引发一系列导致网络崩溃的二次灭绝。让农民加入我们的网络将使我们能够了解她是如何影响网络结构和弹性的。最后，计算机生成的退化网将被用于DEFRA的新农业环境计划——环境管理，来模拟农场的恢复。我们将能够找到最好的方法来恢复构成农场生物多样性的物种之间的相互作用网络。虽然它们的目的是增加农田生物多样性，但很少对农业环境计划的环境影响进行测试。考虑到欧盟每年在这类计划上花费27亿英镑，评估农业环境计划效力的工具是迫切需要的。为什么这门学科令人兴奋、有趣和重要？食物网等生态网络尚未在可持续农业领域得到广泛应用。考虑到网络建设（例如，生态信息学）、理论进步（例如，复杂系统方法）和生物多样性丧失的持续威胁以及雄心勃勃的农业环境计划，现在是一个非常激动人心的时刻，开始使用生态网络作为管理77%被农田占用的土地上生物多样性的实用工具。对社会的更广泛的好处是什么？了解管理景观的生态是实现更可持续农业和保护农田生物多样性的基础。自然和管理栖息地的健康运作为人类提供了必不可少的免费“生态系统服务”。这些包括授粉、害虫控制和水过滤。这些生态系统服务的提供依赖于生物多样性，因此，生物多样性的进一步减少可能会威胁到这些服务，很可能还会威胁到人类。

BACKGROUND: The intensification of arable agriculture over the last 50 yrs has been associated with substantial losses of biodiversity and there is considerable concern that intensive agriculture is incompatible with the conservation of biodiversity. Moreover, there is disquiet that studying indicator groups such as farmland birds is not providing the information needed to foster biodiversity. Our aim is to construct a large ecological network for an organic farm showing how species are linked to each other and then to use a complex systems approach to predict the impact of species loss and species restoration. WHY STUDY THIS SUBJECT AREA? If ecologists, land managers and policy makers are to manage farmland biodiversity sustainably, then they need to understand the ways in which species are linked to each other. Complex systems theory predicts that that the extinction of just a few highly-linked species could lead to a cascade of secondary extinctions, which could cause a complete collapse of the web. Put simply, complex systems such as a farm food web can be very vulnerable to rather small disasters. THE PROPOSAL: We will construct a farm-scale network, which contains plants, insects, birds and mammals as well as insect pest species and the farmer. Once we have constructed the web, which we expect will link about 1000 species to each other in a single network, we will model the impact of species extinction. We will do this by using a computer to simulate primary species loss in the web (by removing species one by one from the network) and measuring the network's robustness in terms of the number and extent of secondary extinctions that follow. A remarkably small number of primary extinctions can cause a trophic cascade. For example, the simulation of a 10% species loss in a 154 species network was sufficient to elicit a cascade of secondary extinctions which led to network collapse. Having the farmer in our network will allow us to ask how she affects network structure and resilience. Finally, the degraded webs generated by the computer will be used to model the farm's restoration using DEFRA's new agri-environment scheme, Environmental Stewardship. We will be able to discover the best way to reinstate the network of interactions between the species that make up the farm's biodiversity. Although they are designed to increase farmland biodiversity, very little testing of the environmental impact of agri-environment schemes takes place. Given that £2.7 billion is spent annually on such schemes in the European Union, tools for assessing the efficacy of agri-environment schemes are badly need. WHY IS THIS SUBJECT EXCITING, INTERESTING AND IMPORTANT? Food webs and other ecological networks have not yet been widely applied to the field of sustainable agriculture. Given the practical advances being made in network construction (for example, in eco-informatics), the theoretical advances (for example, complex systems approaches) and the ongoing threat of biodiversity loss combined with ambitious agri-environment schemes, now is a very exciting time to begin to use ecological networks as a practical tool for managing biodiversity on the 77% of our land occupied by farmland. WHAT ARE THE WIDER BENEFITS TO SOCIETY? Understanding the ecology of managed landscapes is fundamental for achieving more sustainable agriculture and for the conservation of biodiversity on farmland. The healthy functioning of natural and managed habitats provides free 'ecosystem services' essential to mankind. These include, for example, pollination, pest control and water filtration. The delivery of these ecosystem services is dependent on biodiversity, and consequently the services, and very probably mankind, could be threatened by further reductions in biodiversity.