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Biodiversity of urban riparian systems: application of ecological data to the design of environmental planning instruments
thesisposted on 2022-03-28, 21:16 authored by Christopher David Ives
Protecting minimum riparian corridor widths is a common approach by government authorities seeking to mitigate impacts of urban development on riparian and aquatic ecosystems. However, little data exists to verify the efficacy of these policies for biodiversity conservation. This thesis presents research to this end thereby contributing to urban environmental planning practice. -- To promote ecological sustainability, scientific concepts of biodiversity and urban river function need to be connected closely with environmental policy. Following discussion of these themes, the relationship between biodiversity and corridor width was assessed by comparing ant and plant communities from 18 riparian corridors in the Ku-ring-gai Local Government Area, Sydney. Corridor width was not related to ant and plant species diversity but was related to the assemblage composition of both groups. However, substantial data variability remained unexplained. -- This variability was investigated through exploring relationships between biological and environmental data. Reserve perimeter:area ratio and the gradient of the hillslope were identified as significant predictors of ant and plant richness. Corridor width was the best predictor of plant composition overall due to increased habitat heterogeneity in wider corridors, while soil pH was the best predictor of streamside plant communities. Changes in plant composition were driven primarily by exotic plants. Ant composition was influenced by the proportion of adjacent road cover, vegetation type, and reserve connectivity. -- In response to these results the affect of land use on riparian ant communities was assessed through comparing urban and rural catchments in north-west Sydney. Surprisingly, no significant differences in ant diversity or composition were found, but ants responded the dominance of weeds within the riparian zone. -- This work highlights the complexity of biodiversity patterns in urban riparian systems and suggests that in addition to setting minimum corridor widths, managers should consider local and catchment-wide activities and promote active management of the riparian zone.