Impacts and constraints on the existence values of the elements of natural capital stock reviewed above are potentially similar to impacts on the natural, ecological and cultural resources reviewed in previous sections of this report. However, the impact of physical depletion of natural resources will not necessarily be proportional to the impact on the existence values of these resources due to the different values accorded to different resources. Nevertheless, recent media coverage regarding issues such as poor air quality in Hong Kong and the pollution and reclamation of Victoria Harbour, suggests that existence values of important natural resources in Hong Kong would reduce along with resource degradation, and declining assimilative capacity (see Section 5). It is possible, however, that as natural resource or other capital stock becomes scarcer (eg the decline in mangroves, dolphins or well known habitats such as natural wetlands), the existence value of the remaining stock will increase as the possibility of extinction becomes known.

The existence values of the natural capital stock in Hong Kong are very difficult to define. Whilst their role in the assessment of the value (in its widest sense) of the resource has been acknowledged in this report, existence value largely overlaps with other elements of the quality of the resource. For example, declining environmental quality and assimilative capacity or depletion of ecological and natural resources may similarly result in lower existence values, though the relationship is far from being well understood (and as noted in Section 7.3.2, as familiar resources such as flagship species become endangered, existence values may actually increase). Methods of determining non-use values are particularly fraught with uncertainty largely because survey respondents may value resources highly whilst at the same time being unwilling to pay a similar value for their protection. In Hong Kong, where public perception of environmental issues is relatively low, and the priority that these issues should be afforded (eg against economic considerations) is even lower, existence values are not likely to be high and their significance for sustainability is limited.