Dynamics of Murray-Darling floodplain forests under multiple stressors: The past, present, and future of an Australian icon (original) (raw)
Related papers
Forest Ecology and Management, 2012
ABSTRACT Most floodplains have been drastically altered by vegetation clearance and river regulation for human needs. In the mid-latitudes, these degraded ecosystems now face the formidable challenge of rapid warming and drying of climates. If the plant diversity of floodplain forests is to be maintained under future climates, their management must be informed by an understanding of how anthropogenic stressors and environmental gradients shape these ecosystems. We used a field survey to examine the potential drivers (forest structure, flooding and anthropogenic disturbance e.g. grazing and logging) of species richness and composition of Eucalyptus camaldulensis floodplain forests in southeastern Australia. Ninety–three stands were surveyed over 15,500 ha of forest, covering a representative range of forest structures and landscape positions, on a mesic and a semi-arid floodplain. Forest structure was an important predictor of the richness and composition of the understorey of river red gum forests on both floodplains. In particular, richness of native species was associated negatively with increasing canopy cover. On the semi-arid floodplain, where there was recent flooding and grazing, these disturbances were also associated with changes in understorey composition. Recent flooding was associated positively with native species richness, with flooded stands having twice the number of native species found in unflooded stands. Recent grazing was associated with an increase in species richness, which may reflect the concentration of herbivores around flooded areas. Targeted thinning to increase structural diversity among stands may temporarily enhance habitat heterogeneity and plant diversity of floodplain forests. If a diverse, native floodplain forest community is to be sustained in these landscapes, management must include regular flooding that approximates the diversity of historical flooding regimes.
A trickle, not a flood: environmental watering in the Murray–Darling Basin, Australia
Marine and Freshwater Research
Environmental flows are an integral component for the conservation and management of rivers, flood plains and other wetlands in the Murray–Darling Basin. Under the Basin Plan, environmental water is managed by the Commonwealth Environmental Water Office (CEWO) and the states. We assessed CEWO environmental flows (2014–15 to 2018–19), compared our findings with expected outcomes for vegetation in the Basin-wide Environmental Watering Strategy (EWS) and interviewed water managers about the efficacy of environmental watering. Some 21% of CEWO water was delivered as flood events, to 9 of 19 river valleys, inundating 7% of wetland area in those valleys annually and 0.8% of major Basin wetlands. A consistent pattern was the watering of many small wetlands on the South Australian Murray with small volumes (median area 43ha, volume 125ML). Just 12% of the area of river red gum subject to EWS expected outcomes was flooded, and half these events were likely suboptimal to achieve ecological be...
Journal of Environmental Management, 2002
Widespread afforestation has been proposed as one means of addressing the increasing dryland and stream salinity problem in Australia. However, modelling results presented here suggest that large-scale tree planting will substantially reduce river flows and impose costs on downstream water users if planted in areas of high runoff yield. Streamflow reductions in the Macquarie River, NSW, Australia are estimated for a number of tree planting scenarios and global warming forecasts. The modelling framework includes the Sacramento rainfall-runoff model and IQQM, a streamflow routing tool, as well as various global climate model outputs from which daily rainfall and potential evaporation data files have been generated in OzClim, a climate scenario generator. For a 10% increase in tree cover in the headwaters of the Macquarie, we estimate a 17% reduction in inflows to Burrendong Dam. The drying trend for a mid-range scenario of regional rainfall and potential evaporation caused by a global warming of 0.5 degree C may cause an additional 5% reduction in 2030. These flow reductions will decrease the frequency of bird-breeding events in Macquarie Marshes (a RAMSAR protected wetland) and reduce the security of supply to irrigation areas downstream. Inter-decadal climate variability is predicted to have a very significant influence on catchment hydrologic behaviour. A further 20% reduction in flows from the long-term historical mean is possible, should we move into an extended period of below average rainfall years, such as occurred in eastern Australia between 1890 and 1948. Because current consumptive water use is largely adapted to the wetter conditions of post 1949, a return to prolonged dry periods would cause significant environmental stress given the agricultural and domestic water developments that have been instituted.