Biodiversity on International Borders Requires Solid Inventories

Over 2500 scientists recently proposed that building a wall on the United States–Mexico border may threaten biodiversity (Peters et al. 2018). Indeed, the construction of walls, fences, and barriers along borders poses an increasing threat to the local biodiversity (Linnell et al. 2016, Fowler et al. 2018), including rapid population decline of Kashmir markhor along the India–Pakistan border (Ellison 2014) and grey wolf along the Slovenia–Croatia border (Linnell et al. 2016). However, these studies typically focus on the policy implications for large transboundary flagship species (Ellison 2014; Ogden 2017), while we know little on a great many other ­species living along the border. Given that the borders between countries often coincide with important landscape features such as mountains ridges and rivers, they are located on strong ecological gradients that support high biodiversity. For example, 8 out of the 19 hotspots for endemic plant species in China are located along its borders (Huang et al. 2016). In some cases, borders additionally experience lower human activities, for instance, due to a restricted accessibility in military control areas or military legacies such as unexploded bombs, which has made the border between South and North Korea sanctuary to nearly 3000 species (Kim 1997).