The survey then asked respondents to choose between various policy options that had different environmental impacts and different costs. Specifically, total willingness to pay (in present value terms) to increase the frequency of waterbird breeding from every 10 years to 4 years, to increase native fish populations from 30% to 50% of original levels, to increase the area of healthy native vegetation from 50 to 70%, and to improve wateibird breeding habitat quality in the Coorong was AUD 13 billion (USD 14 billion). The authors stress that, due to the uniqueness of the Coorong, this value cannot be used to estimate the value of other watercourses in Australia, and further surveys are required.