The Blue Mountains upland peat swamps (Temperate Highland Peat Swamps on Sandstone) are a unique geomorphic system, situated on the sandstone escarpment west of Sydney, NSW Australia and north and south along the eastern seaboard. The swamps are a common feature in that region, but are of such natural value that they are listed under State and Federal legislation as an endangered ecological community (Commonwealth Environment Protection and Biodiversity Conservation Act 1999; NSW Threatened Species Conservation Act 2005).
Urban development across the Blue Mountains region, particularly in the escarpment and plateau areas above the swamps, has altered catchment permeability and consequently, hydrology of the swamps (1). Alteration of hydrology and introduction of extraneous sediments has been linked with a loss of structural integrity, change to the sedimentary profile of the swamps and lower water content retention (1).
In this paper, we used a combination of abiotic, biotic and functional indicators to try to understand how urban development affects swamp ecology. We sampled piezometers from within twelve upland swamps with varying urban impact: from pristine to those highly connected to their urban landscape. We measured hydraulic conductivity, water quality, groundwater invertebrates and cotton strip decomposition over 12 months.
We found that water from urbanized catchments retained nutrients and other pollutants through the swamp. In turn, as pollutants, including EC, alkalinity, temperature and nutrients associated with stormwater infrastructure increased, stygofaunal communities responded by increasing biodiversity and populations. More importantly though, decomposition rates increased with catchment urbanization. Higher decomposition rates, in concert with expected further water temperature intensification due to climate change, may result in organic matter losses and decreased organic matter accumulation. In turn, as the ratio of sands to organic matter rise with increasing urbanization, water flow intensity and variability may surge, reducing residence time, enhancing erosive capacity and affecting water quality downstream.
Results suggest that natural functioning of upland peat swamps in the Blue Mountains is already being compromised by urbanization, evidenced by altering hydrology, water quality, increasing productivity and alterations to stygofauna assemblages. The importance of peat swamps, both locally and globally in carbon storage and the current lack of knowledge of their aquatic and terrestrial invertebrate fauna, requires a greater emphasis in understanding functional processes in order to more fully understand the impact of multiple stressors on these fragile ecosystems.