The tropical rivers and groundwater systems of northern Australia contain approximately 70% of Australia’s freshwater resources (Hamilton and Gehrke 2005). These tropical river systems provide ecosystem services that underpin the survival and well-being of people; multiple industries, such as pastoralism and horticulture; activities, such as cultural resource management and recreational fishing; and the continued health and functioning of the ecosystems of the region.
An ongoing drought in southern Australia and increasing awareness of the value of water worldwide is drawing attention to the potential for development in northern Australia. Any development in the tropical rivers region will have impacts on the ecosystems and ecosystem services of tropical river systems. These impacts will also likely affect the uses and benefits underpinned by these ecosystem services.
This project provides assessments of the potential impacts of future development scenarios on the ecosystem services of Australia’s tropical rivers. In doing so, this work builds on existing knowledge of the values and assets of Australia’s tropical rivers by identifying the ecosystemservices of Australia’s tropical river systems, their contribution to human well-being, and the drivers that impact on them. The study assess the impacts of potential development scenarios through: (1) estimating the economic value of four particular ecosystem services; and (2) analysing key changes in the past for insight into the future. It does this through three case studies: the Fitzroy River in Western Australia (WA), the Daly River in the Northern Territory (NT) and the Mitchell River in Queensland (Qld).
Economic valuation
The economic valuation was undertaken using the choice modelling method, selected for its ability to enable the measurement of people’s willingness to pay for the non-use values associated with tropical river ecosystem services, and to elicit preferences for a number of environmental attributes at the one time. A questionnaire about the future of each case study river system was presented to people living in each river catchment, the capital city of the state/territory each catchment is in, and capital cities in southern Australia. Respondents were asked about their preferences for: (1) provision of floodplain habitat in good environmental condition; (2) provision of river conditions for quality recreational fishing; (3) provision of species and habitat important to Aboriginal customary activity at waterholes; and (4) production from irrigated agriculture.
Different levels for each of the four ecosystem services were identified: low, medium and high. The lowest levels are: (1) the smallest area of floodplain in good environmental condition, (2) the worst quality of the river for recreational fishing, (3) waterholes important to Aboriginal people are in poor condition, and (4) the lowest level of income from irrigated agriculture. The medium and highest levels represent improvements on each of these.
The results of the economic valuation include estimates of willingness to pay (implicit prices), aggregate willingness to pay, and compensating surplus from a series of different models. Respondents from each targeted population express a value for improvements in all four ecosystem services whether they have visited or intend to visit the region or not. In estimating value, we calculated a few different types of models that make different assumptions about how people make choices, so we present a range of estimates.
