Quantifying Costs of Urbanisation: Wetland Loss and Impacts in a Rapidly Developing Global City

Abstract As cities grow, natural ecosystems decline through conversion to urban environments. Cities are often viewed as biodiversity wastelands, but they can be hotspots of global biodiversity. Urban biodiversity emphasises two fundamentals. First, people living in cities enjoy wildlife and second, there is virtually no planning for species that co-inhabit our cities. If urban biodiversity was a significant part of planning, then we would be far better at integrating green infrastructure into expanding urban environments. Wetlands are among the most important and productive ecosystems in the world. They are the main suppliers of fresh water for human use and provide habitat to critical fauna and flora. In urban areas they are a vital link to nature and social cohesion. Currently, there is an absence of wetland inventory quantifying loss and changes overtime. Hence the broad impacts of urbanisation on wetland loss are difficult to assess. We explored wetland loss and created a wetland inventory for Western Sydney, Australia, one of the world’s fastest growing urban regions. We used satellite imagery to determine wetland number and type, and calculated changes in wetland surface area from 2010-2017. Broad changes to land use were also quantified. We developed species distribution models of a common urban wetland turtle ( Chelodina longicollis ) that people interact with regularly or have as pets. Chelodina longicollis utilises both aquatic and terrestrial environments, and we determined if changes in distribution were associated with changes in the wetland inventory and urbanisation. Most local government areas (LGA) experienced a decrease in wetland surface area from 2010-2017, ranging from -1% (Cumberland) to -21% (Blacktown). Majority of LGAs experienced a decrease in wetland density, with wetland densities declining by 25% (Blacktown). All LGAs experienced an increase in urban land use, ranging from 3-12%, which was associated with high rates of wetland loss. Changes in turtle distribution over the decade reflects a southern distribution shift away from where wetland losses were concentrated. We estimated that ∼40,000 individual turtles were displaced or killed due to wetland loss and urbanisation. Urbanisation was the leading cause of wetland loss and degradation in Western Sydney between 2010 and 2017. Wetlands provide critical green infrastructure and significant green space for social cohesion in urban areas. Integration of current wetlands, or the creation of functional wetlands, is key for sustainable development of urban landscapes. Urban wetlands (natural and constructed) may provide “biodiversity arks” for endangered species and facilitate community led conservation programs.