The value of Australia’s tropical river 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 ecosystem services of Australia’s tropical river systems, their contribution to human well-being, and the drivers that impact on them. The study assesses 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 There were some similarities across river systems for the different types of models:
(a) Respondents for all three rivers value the highest level condition of waterholes important to Aboriginal people the most.
(b) Respondents for all three rivers living in a city are willing to pay more for the highest levels of area of floodplain in good environmental condition, quality of the river for recreational fishing and condition of waterholes important to Aboriginal people than the medium levels, and more for the medium level of income from irrigated agriculture than the highest level. This indicates that people generally want to see the maintenance of tropical river systems in excellent condition for environmental, recreational and cultural values and uses, and they value medium rather than large scale expansion of irrigated agriculture.

Resilience analysis: analysing key changes in the past for insight into the future.

The second approach to assessing the impacts of potential development on tropical river ecosystem services uses resilience theory to guide the exploration of complex interactions between the social and ecological variables and processes of the tropical rivers region.

Our survey of the history of the tropical rivers region enables the observation of several cycles of change, called ‘adaptive cycles’ in resilience theory, and insight into what might happen next given current trajectories. One example of the next phase of development in the tropical rivers region could be borne of a significant development of water resources. As existing research for the tropical rivers region seems to indicate, and as experience in the Murray-Darling basin of southern Australia dictates, any significant modification of stream flows and the flow regime may see the social-ecological system of the tropical rivers region move through the current phase of conservation and into a collapse similar to that seen in the Murray-Darling system. Alternatively, the system could shift to a new state organised around significantly different land-uses that do not require large input of water.

Resilience theory also brings attention to the important role that thresholds play in managing the capacity of complex adaptive social-ecological systems to continue to provide the ecosystem services that are valued and critical for human well-being. Based on the estimates of willingness to pay for each of the ecosystem services reported above, we suggest that shifting over these thresholds will also significantly impact the value associated with each ecosystem service in terms of an associated economic impact on community welfare.