Fragments, functions and flows - the scaling of biodiversity and ecosystem services in urban ecosystems

城市地区只占地球陆地面积的2.8%，但超过50%的人口生活在城市地区，而且这一比例还在迅速增长。如此高度的人口集中产生了各种各样的重要后果。这些与环境的关系最近引起了媒体、压力团体、政策制定者、研究人员以及地方和国家政府的极大关注。特别令人关切的是，如何才能最有效地改善城市地区所经历的环境条件，改善城市居民与自然环境之间的互动程度，以及城市地区对更大范围提供生态系统服务的贡献。这就提出了一个关键问题：城市地区生物多样性和生态系统服务之间的关系的形式，城市地区的结构(不同种类和程度的不透水和渗透表面的空间结构；城市形态)如何影响这些关系，从而如何最好地管理现有结构，以及如何规划未来结构以达到最佳效果。尽管近年来人们对城市地区生物多样性和生态系统服务的水平和分布的了解有了很大的改善，但城市地区对生物多样性和生态系统服务之间的关系的研究非常少(主要的实证研究整理中基本上没有)。事实上，这些环境构成了重大和不同寻常的挑战：--城市景观高度分散，很大一部分区域被建筑物和路面封闭；--绿地镶嵌在复杂的建筑物和道路中，对整个城市景观中的生物多样性和生态系统服务的提供施加了重大限制和方向性；--人类对这些环境的管理强度，可能会产生生态系统服务所依赖的能量、物质和生物多样性流动的空间模式和规模，而这种模式和规模是不会自然发生的；而且，--城市地区的人口聚集通常需要较少的常规方法在城市地区进行生态研究，包括更多地与公众接触，减少对大型设备的使用的依赖，这对一般人来说是“不受限制的”。为了确定这些生物多样性-生态系统服务关系，加深理解并测试这种理解，我们对这个项目的总体方法包括五个主要步骤。我们将：-表征城市地区的空间生态结构；-确定生物多样性-生态系统服务关系以及连通性对它们的影响；-在选定的情况下确定生物多样性的流动和服务提供；-试验性地扰乱这些流动以确定对生态系统服务提供的影响；以空间清晰模型的形式整合这些发现，这将构成地理信息系统模型的“生态系统服务”层的基础。这将使我们能够加深理解，并为利益相关者(如规划者、当地人和非政府组织)提供说明，说明如何测试不同发展建议的“情景”，为基于健全的科学和利益相关者参与的决策提供支持。

Urban areas cover just 2.8% of the Earth's land area, but over 50% of the human population lives in them, and these proportions are growing rapidly. Such heavy concentration of people has a wide variety of important consequences. Those for their relations with the environment have attracted much recent attention from the media, pressure groups, policy makers, researchers, and local and national government. Of particular concern have been how improvements can most effectively be made to the environmental conditions experienced in urban areas, to the levels of interaction between urban dwellers and the natural environment, and to the contribution of urban areas to the broader scale provision of ecosystem services. This raises the key issue of the form of relationships between biodiversity and ecosystem services in urban areas, how the structure of urban areas (the spatial structure of the different kinds and extents of impermeable and permeable surfaces; urban form) influences these relationships, and thus how the existing structure can best be managed and how future structure can be planned to best effect.Although understanding of the levels and distributions both of biodiversity and of ecosystem services in urban areas has improved dramatically in recent years the relationships between biodiversity and ecosystem services have been extremely poorly studied in urban areas (and are largely absent from major collations of empirical studies). Indeed, these environments pose significant and unusual challenges:- the urban landscape is highly fragmented, with large portions sealed by buildings and paving;- greenspaces are embedded in a complex mosaic of buildings and roads that imposes major constraints and directionality on the flows of biodiversity and ecosystem service delivery across the urban landscape;- the intensity of human management of these environments can give rise to spatial patterns and scales of flows of energy, materials and biodiversity on which ecosystem services depend that would not naturally occur; and,- the very aggregations of people that give rise to urban areas typically necessitate less conventional approaches to conducting ecological research therein, involving greater engagement with the general public, and less dependence on the use of large pieces of equipment, which is "out of bounds" to the general population.In order to determine these biodiversity-ecosystem service relationships, develop deeper understanding and to test this understanding our overall approach to this project involves five main steps. We shall:- characterise the spatial ecological structure of urban areas;- determine biodiversity-ecosystem service relationships and the influence of connectivity on them;- determine the flows of biodiversity, and service delivery in selected cases;- experimentally perturb those flows to determine the impact on ecosystem service delivery; and- integrate these findings in the form of spatially explicit models which will form the basis of an "ecosystem service" layer for GIS models.This will enable us to deepen understanding, and to provide illustrations for stakeholders (such as planners, local people and NGOs) as to how "scenarios" of different development proposals might be tested, to provide support for decisions based on sound science and stakeholder engagement.