National parks in the United States represent a treasure trove of natural, historical, and recreational landscapes, but their health is at risk. A comprehensive new study on the climate-change vulnerability of national parks, published in Conservation Letters, has found that 77% of America's national park sites are highly vulnerable to climate change. According to the study, most of these parks are at risk of at least one potentially transformational impact, such as fire, drought, pests or diseases or sea-level rise.