| الوصف: |
Global biodiversity is declining faster than at any time in human history. This loss is largely attributed to human activities, in particular urban, industrial and agricultural development. Biodiversity offsetting seeks to balance the environmental impacts from development through the generation of measurable gains in biodiversity that compensate for loss. To achieve No Net Loss or a Net Gain in biodiversity, the biodiversity gains from offsetting must be at least equivalent or greater to the biodiversity losses from development. But while losses from development are typically immediate, gains from offsetting are generated over longer timeframes, often after the impact has occurred. Determining equivalence between an impact and an offset thereby requires projecting the gains that will be generated over an offset management period. As biodiversity is in decline, gains may be generated from averting further loss in biodiversity, as well as from improving the biodiversity at an offset site. To determine the gains attributable to an offset, assumptions must be made about changes in biodiversity with and without the offset. These assumptions have serious implications on achieving a No Net Loss outcome from offsetting, however they may not always be drawn from empirical data. In this thesis, I review the assumptions used to calculate gains from offsets in two loss-gain exchange case studies under Victorian offsetting policy. These gains were used to offset losses in native vegetation from permitted development impacts, and reflect the gains from projected averted loss and improvement in native vegetation over the 10-year offset management periods. The assumptions of gain vary between the case studies according to the native vegetation condition, foregone land use entitlements and proposed management activities, but the assumptions are not entirely explicit nor supported by empirical data. When compared to available data on native vegetation change without an offset, I reveal that the assumptions of gain from averted ... |
