Prioritising wetlands subject to secondary salinisation for ongoing management using aquatic invertebrate assemblages: a case study from the Wheatbelt Region of Western Australia

Abstract

Secondary salinisation is recognised worldwide as a threat to aquatic biodiversity. Wetlands in the Wheatbelt Region of Western Australia are particularly affected as a result of clearing of deeprooted native vegetation for agriculture. Between 1996 and 2001, the Western Australian government nominated six natural diversity recovery catchments (NDRCs), being catchments with high value and diverse wetlands in need of protection. One, the BuntineMarchagee NDRC, supports approximately 1000 wetlands in varying states of salinisation. The challenge is to prioritise these wetlands for ongoing management. In this paper we propose an approach to prioritise representative wetlands using aquatic invertebrates. On the basis of hydrology, salinity and remnant vegetation, 20 wetlands covering a range of salinities were selected for sampling of water quality and aquatic invertebrates. Of the 202 taxa recorded, most endemic taxa occurred in fresh/brackish wetlands, while hypersaline wetlands supported predominantly cosmopolitan species. Taxa richness was greater in fresh/brackish than saline and hypersaline wetlands, with conductivity explaining 83 % of between-wetland variation in taxa richness. Classification using invertebrate assemblages separated fresh/brackish, saline and hypersaline wetlands, with greatest between-year variability within saline and hypersaline sites. Wetlands were ranked using taxa diversity, presence of conservation-significant taxa and temporal similarity. Mean rank across indices provided the final overall order of priority. Hypersaline wetlands were ordered separately to the fresher water wetlands (fresh/brackish and saline) so that priority for future management was detailed for both types of wetlands. The analysis indicated that although fresh/brackish sites support the highest biodiversity, naturally saline sites also supported wetland assemblages worthy of ongoing protection.

Coastal Wetlands: Ecosystems Affected by Urbanization?

“…In summer, freshwater varied between 8 • C and 14 • C, and was higher mainly in shallow areas, in contrast to winter, when the temperature was greater at stations close to the mouth due to the stabilizing effect of the sea. In addition, the increase in surface water temperature regulates energy flows and evaporation rate increases, thereby affecting the water level [20,34,56], as well as influencing the generation of secondary salinization processes, mainly in urban wetlands, as recently described in wetlands of western Australia [57], South Africa [58] and North America [59]. The increase in salinity due to evaporation can become a serious threat to ecological structure and functioning.…”

Adaptive management for soil ecosystem services

“…In arid regions, rapid evaporation of impure irrigation water leaves behind salt residues on the soil surface, and waterlogging of soil with natural salt deposits may mobilize salt upwards (Sumner, 1995). Loss of ecosystem services associated with salinization due to agricultural intensification is not a new problem e it was a significant contributor to the dissolution of the Sumerian nation-state in~1800 BCE (Jacobsen and Adams, 1958), and losses of riverine and wetland ecosystem services from saline runoff underscores the potential of salinization for long-term, watershed-scale impacts (Hart et al, 1991;Delaney et al, 2015). Indeed, the agricultural and ecological effects of soil salinization are widespread (e.g., Rietz and Haynes, 2003;Houk et al, 2006) with approxiamately 50% of global agricultural soils experiencing some degree of salinization, resulting in agricultural costs of roughly US $12 billion annually (Smedema and Shiati, 2002;Pitman and L€ auchli, 2002).…”