Evaluating The Landscape-scale Benefits Of Sustainable Urban Drainage Systems For Freshwater Biodiversity

世界上一半以上的人口现在生活在城市地区，城市地区的持续快速扩张为保护生物多样性提供了挑战和机遇。城市化通常与稀有或对污染敏感的物种的丧失、群落的整体变化以及入侵动植物的传播和优势有关。城市绿色基础设施(GI)的发展有可能为这些问题提供平衡。城市地理标志涵盖了广泛的生态系统特征，包括林地、草原和草地，以及淡水特征。有效的GI的发展有可能提供增强的生态系统服务、生物多样性的增加和娱乐等社会效益。可持续的城市排水系统(SUDS)是GI的一个常见的“蓝色”组成部分。这些人工水体的主要设计目的是截留城市集水区的地表排水，通过沉淀物的沉降和污染物的吸收/分解来改善水质。这类肥皂水主要由小池塘和其他人工湿地组成，也为增强城市淡水生物多样性提供了机会；四个“肥皂水支柱”强调了它们在水质、数量、生物多样性和舒适性方面的作用。通过一些研究评估了肥皂水与当地生物多样性的作用。已经有证据表明，肥皂水可能是稀有物种的重要栖息地，对保护物种也很重要。尚未得到很好证实的是，它们在物种丰富度、种群连通性和种群内和种群间的遗传多样性方面对景观或集水区规模的多样性产生了更广泛的影响。许多淡水类群高度分散，肥皂土可能成为其他天然池塘和包括河流在内的其他类型淡水生态系统的重要垫脚石栖息地。由于这种潜在的连通性，肥皂土可能允许原本孤立的种群在包括自然和城市栖息地的生态系统网络中作为稳定的集合种群持续存在。在自然淡水往往稀缺的广大城市地区，肥皂土可能在自然特征和其他地点(如花园池塘)之间提供联系，从而增加种群迁移和基因流动方面的景观渗透性。众所周知，与城市化相关的生境碎片化会影响基因流动，遗传多样性的减少可能会影响适应不断变化的环境的能力。鉴于许多物种范围随着气候变化而显著北移，这种渗透性可能也是让物种绕过城市屏障的关键。然而，提高渗透性也有不利的一面；肥皂对增强生物多样性的价值必须与庇护和鼓励病媒和有害生物传播的价值进行权衡，在规划肥皂时考虑到这一风险-回报比率。苏格兰规划政策将退伍军人事务部确定为我们长期环境绩效和气候适应能力的重要组成部分。通过绿色基础设施战略干预(GISI)等举措，苏格兰的GI目前正在进行大量投资。GISI是目前欧洲区域发展基金在苏格兰的方案的一部分，为苏格兰城市贫困地区的多功能GI提供资金。除了为当地的人类和自然创造利益外，这些地点还将作为示范地点，展示地理信息系统的价值以及它如何带来多重好处。通过这项持续的投资，评估结果并确定如何实施此类开发，以最大限度地惠及当地生物多样性，同时履行其他功能，如城市水资源管理，是至关重要的。

More than half of the world's population now lives in urban areas and the ongoing rapid expansion of urban areas provides challenges and opportunities for the conservation of biodiversity. Urbanisation is commonly associated with loss of rare or pollution sensitive species, overall change in communities and the spread and dominance of invasive plants and animals. The development of urban green infrastructure (GI) has the potential to provide a counter-balance to such issues. Urban GI encompasses a wide range of ecosystem features including woodland, grasslands and meadows, and freshwater features. The development of effective GI has the potential to provide enhanced ecosystem services, biodiversity gain and societal benefits such as recreation.Sustainable Urban Drainage Systems (SUDS) are a common 'blue' component of GI. These are artificial waterbodies principally designed to intercept surface drainage in urban catchments, improving water quality by allowing settlement of sediment and absorption/breakdown of pollutants. Such SUDS, mostly consisting of small ponds and other artificial wetlands, also present an opportunity for enhancing urban freshwater biodiversity; the four 'SUDS pillars' emphasise their role in relation to water quality, quantity, biodiversity and amenity.The role of SUDS in relation to local biodiversity has been assessed through a number of studies. There's already evidence that SUDS can be important habitats for rare and important to conservation species. What has not been well established is their broader influence on diversity at the landscape or catchment scale, in terms of species richness, population connectivity and genetic diversity within and between populations. Many freshwater taxa are highly dispersive and SUDS can potentially act as important stepping-stone habitats both from other natural ponds and other types of freshwater ecosystems including rivers.Due to this potential connectivity, SUDS might allow otherwise isolated populations to persist as stable metapopulations within an ecosystem network that includes both natural and urban habitats.In extensive urban areas, where natural freshwaters are often scarce, SUDS may provide links between natural features and other sites such as garden ponds and therefore increase landscape permeability both in terms of population movement and gene flow. Habitat fragmentation associated with urbanisation is known to influence gene flow, with reduction in genetic diversity potentially impacting on the ability to adapt to changing environments. Given significant northwards shifts of many species ranges with changes in climate, such permeability may also be critical in allowing species to bypass urban barriers. Enhanced permeability can have a downside however; the value of SUDS for enhancing biodiversity must be weighed against the value for harbouring and encouraging spread of disease vector and pest organisms, with the planning of SUDS undertaken with consideration of this risk-reward ratio.Scottish Planning Policy identifies GI as an essential part of our long-term environmental performance and climate resilience. Significant investment is currently taking place in GI in Scotland through initiatives such as the Green Infrastructure Strategic Intervention (GISI). The GISI is part of the current European Regional Development Fund programme in Scotland and funds multifunctional GI in deprived areas of urban Scotland. As well as creating benefits for people and nature in the local areas, the sites will act as demonstrator sites, showing the value of GI and how it can deliver multiple benefits.With this ongoing investment it is vital to evaluate the outcomes and determine how such developments can be implemented to maximise benefits for native biodiversity whilst performing other functions such as urban water management.