Oral Presentation 9th Australian Stream Management Conference 2018

Is geochemical contamination from urban development contributing to weed invasions in high conservation value wetlands (#95)

Rani Carroll 1 , Ian A Wright 1 , Jason K Reynolds 1
  1. Western Sydney University, Penrith

Blue Mountains Upland Swamps are unique ecosystems that are restricted to 3200ha within the Blue Mountains and are listed as an endangered ecological community under the Environment Protection and Biodiversity Conservation Act 1999 (Cwlth) and Threatened Species Conservation Act 1995 (NSW). Geochemistry of water, sediment and foliage samples was assessed within two urbanised and two naturally vegetated swamp catchments. Urban swamps were observed to exhibit elevated pH by 1.45 pH units and electrical conductivity was 4.5 times higher than naturally vegetated swamps. Concentrations of calcium, bicarbonate and potassium differed between catchment types within water, sediment and foliage tissue. Concrete is suspected to contribute much of the geochemical contamination within urban catchments due to its gradual dissolution and mobilisation of ions such as calcium, potassium and bicarbonate. Urban development is also recognised to contribute to erosion, channelisation and water pollution within Blue Mountains Upland Swamps. Urbanisation is associated with Key Threatening Processes in the swamps including altered natural hydrology, exotic weed invasions and altered fire frequency. However, the ecological implications of urban water chemistry on these sensitive swamp communities is not well-known. We suspect that urban swamp geochemistry may favour exotic plant species. Improving our understanding of how urban development may affect these unique ecosystems is essential to guide management practices, for example exploration of alternative materials to concrete for use in sensitive, poorly buffered environments, and promote conservation.

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