Role of protected areas in mitigating range loss and local extinctions of terrestrial mammals.

Protected areas (PAs) are a major tool in biodiversity conservation, but the extent to which they mitigate species declines is often unclear. We evaluated the effectiveness of PAs in mitigating range contraction and local extinction for 483 terrestrial mammal species. We used expert-based species range maps from the 1970s and compared them with current distributions to estimate changes in range area and PA coverage over the last 5 decades. We used generalized boosted models and propensity score matching to assess the effectiveness of PAs in mitigating species declines in landscape units sharing environmental features but differing in protection status. On average, mammal species were extirpated across one third of their ranges from 1970 to 2015, and 86% of this range contraction occurred outside PAs. In areas protected continuously since the 1970s, extirpation rates were half that in matched landscape units that were never protected. Areas protected since the 1970s also had lower extirpation rates compared with matched areas that became protected later. Lower species extirpation and range contraction rates were also correlated with greater area encompassed by PAs. Although the proportion of species ranges encompassed by PAs seemingly increased by 12% from 1970 to 2015, this increase may be largely attributed to the loss of species range area outside PAs rather than the strategic expansion of PAs. Our results showed that PAs can mitigate range loss and local extinctions for mammals and highlighted that PAs need to be maintained continuously over long time frames to have positive effects on biodiversity. Our findings suggest that downgrading, downsizing, and degazettement of PAs can lead to biodiversity declines, whereas the strategic achievement of targets, such as protecting 30% of land area by 2030, could facilitate species persistence.