Climate change threatens the health and survival of urban trees, with more than half of species already feeling the heat, according to a new study. City-dwelling oaks, maples, poplars, elms, pines and chestnuts are among more than 1,000 tree species flagged at risk due to climate change. Scientists want better protection of existing trees and for drought-resistant varieties to be planted. Trees have cooling effects and provide shade, making cities more liveable. Many trees in urban areas are already stressed because of climate change, and as it gets warmer and drier, the number of species at potential risk will increase, said Manuel Esperon-Rodriguez of Western Sydney University in Penrith, Australia. …Of the 164 cities analysed, more than half of tree species are already at risk in some cities due to rising temperatures and changes in rainfall. And by 2050, this proportion is predicted to rise to more than two-thirds.