Urban greenery facing climate risks

A study using GBIF-mediated data published this week in Nature Climate Change shows that more than half of trees and shrubs in cities worldwide are currently facing temperatures and precipitation exceeding their tolerance levels. Originally shared as a preprint in May, the study estimates that by 2050 more than 70 per cent of species will be at risk.

Using the Global Urban Tree Inventory researchers identified relevant species found in in 164 cities across 78 countries worldwide. Based on a list of 3,000+ species they obtained GBIF-mediated species occurrences and vegetation plot data from sPlotOpen. Combined, this dataset was used to extract climate variables to characterize baseline climate niches for all species. The authors estimated climate risks by examining changes to five climatic variables as projected under Representative Concentration Pathway (RCP) 6.0 by the year 2050.

While 100 per cent of species in certain cities have already exceeded their tolerance levels—such as Barcelona, Niamey and Singapore, all cities investigated are predicted to undergo significant increases in temperature variables. The highest increases are predicted to occur in Helsinki, Winnipeg and Minneapolis, however, climate risks were higher in cities with low readiness score (i.e. vulnerability to climate change and capacity to strengthen resilience), such as Pretoria and New Delhi.

Ironically, the study suggests that in addition to recreational value, urban species planted to help mitigate effects of greenhouse gas emissions by sequestering carbon through photosynthesis face severe climate risks, undermining their roles in climate adaptation and other ecosystem services they provide, such as cooling by providing shade and dissapating urban heat through evapotranspiration.