A warming climate is increasingly threatening the existence of trees in cities, according to a major international study that attempts to assess the risk to various urban tree species in the context of increasingly hotter and drier years. And pollution affects urban green oases.

Under current conditions of more intense heat waves and too little precipitation, somewhere between 56 and 65% of urban trees are at risk, and by 2050, when warming trends continue, this proportion could rise to 68-76%. The heat stress experienced by trees will be experienced by more and more species.

The researchers arrived at these results by examining data on more than 3,000 species of trees and shrubs from 78 countries and calculating the climate resilience of each species to current conditions, as well as to those projected in 2050, when things will be worse.

Species valued include oaks, poplars, maples, and chestnuts.

Many cities plant trees that may not cope well with a warming climate, but wealthier cities can afford irrigation systems that partially compensate for reduced rainfall.

Researchers from several universities, such as Western Sydney University (Australia) and Jules Verne University of Picardy (France), worked on this study.

The study is published in Nature Climate Change

Sources: phys.org, BBC