In general, rare plants are plants that have very limited ranges or that exist in low numbers. Some are naturally rare, such as those adapted to geographically specific soils, microclimates or pollinators. Such plants are particularly vulnerable to the effects of climate change, various human land uses, and exotic plant invasions. Other native plants may have become rare more recently as a result of these factors. National parks keep track of the rare species occurring within their boundaries, focusing on those species that have declined to the point of requiring Endangered Species Act protection. Data collected about declines in rare plant populations helps park managers determine how those declines can best be mitigated.