The importance of protected areas for species undergoing distribution changes

The value of Protected Areas for wildlife will diminish if the species for which they were originally designated are pushed out of their boundaries by changing temperatures, or if they are infiltrated by invasive species that are harmful to native species. Here, I assess the performance of Protected Areas against this background of distributional change. I found that Protected Areas have facilitated the range expansions of the six wetland bird species that have recently colonised the UK, both as sites at which breeding first occurs and as locations where substantial populations can establish before spreading to unprotected land. In contrast, non-native species did not initially ‘invade’ Protected Areas, but subsequently colonised them as their populations grew. I complemented this analysis with a field research project in a Mexican Biosphere Reserve. Here, Strictly Protected Areas were resistant to non-native species (as in the UK), and important for species undergoing global population declines. However, partially-protected locations with habitat modification provided opportunities for both non-natives and native generalists. Consequently, modified areas were characterised by higher local-alpha diversity than relatively natural areas, although they contained relatively similar suites of species across different biogeographical zones. Thus, evaluating the impact of Protected Areas depended on the metric of biodiversity change considered, and on the level of protection. Similar patterns were revealed on a global scale (considering 118 countries). Range expansions (colonisations and introductions) have outpaced countrywide extirpations over the last two centuries, resulting in a c.4% average net increase in national breeding bird avifaunas, even though gamma- and beta-diversity have decreased. Protected Areas may have promoted ‘beneficial’ change in this context; there were more colonisations and fewer extirpations in countries with more protected land. Protected Areas will remain crucial as a part of future conservation strategies to protect biodiversity in an era of increasing distributional dynamism.