Quantifying the cumulative impact of winter habitat loss on a critically endangered migratory parrot

Habitat loss is a major driver of biodiversity decline, often occurring in a slow-paced, piecemeal way. The cumulative impacts of such loss can be substantial for threatened species but are challenging to quantify and thus factor into planning decisions—particularly for mobile species with large ranges and irregular settlement patterns. We combined remote sensing and population viability analysis to estimate the cumulative impact of various winter habitat loss scenarios on the critically endangered, migratory swift parrot Lathamus discolor in south-eastern Australia. Swift parrots suffer from predation during nesting and logging of their Tasmanian breeding habitat, but the Hunter-Central Coast (HCC) of New South Wales is an important wintering area for the species and also amogst the most rapidly developing. If threats from predation and logging in Tasmania are addressed but habitat loss occurs throughout the species' wintering range at the rate observed in the HCC, the swift parrot population is expected to decline by 16% over 50 years. If observed rates of habitat loss in the HCC continue, halve, or double, the additional impact from that region alone on the swift parrot population could lead to a decline of 32% over 100 years. Our study emphasizes the need to avoid cumulative impacts across the full range of mobile species to help prevent their extinction.