Climate change threatens the health and survival of urban trees and the various benefits they deliver to urban inhabitants. Here, we show that 56% and 65% of species in 164 cities across 78 countries are currently exceeding temperature and precipitation conditions experienced in their geographic range, respectively. We assessed 3,129 tree and shrub species, using three metrics related to climate vulnerability: exposure, safety margin and risk. By 2050 under Representative Concentration Pathway 6.0, 2,387 (76%) and 2,220 (70%) species will be at risk from projected changes in mean annual temperature and annual precipitation, respectively. Risk is predicted to be greatest in cities at low latitudes—such as New Delhi and Singapore—where all urban tree species are vulnerable to climate change. These findings aid the evaluation of the impacts of climate change to secure long-term benefits provided by urban forests.
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The data generated and analysed for this study have been deposited on Figshare: https://figshare.com/projects/Climate_change_increases_global_risk_to_urban_forests/144039
All data were edited and analysed in R v.4.0.5 (ref. 52) and Microsoft Excel v.16.17.27 (201012). The complete codes used to generate and visualize the results reported in this study have been deposited on Figshare: https://figshare.com/projects/Climate_change_increases_global_risk_to_urban_forests/144039
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We gratefully acknowledge L. Staas for her support of the project and S. Allen for programming assistance. M.E.R., L.J.B., S.A.P., P.D.R., M.G.T. and R.V.G. received funding from the Hort Frontiers Green Cities Fund, part of the Hort Frontiers strategic partnership initiative developed by Hort Innovation, with co-investment from Macquarie University, Western Sydney University and the NSW Department of Planning, Industry and Environment and contributions from the Australian Government. We thank P. B. Reich for his feedback.
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Changes (i.e. exposure) in maximum temperature of the warmest month (A), minimum temperature of the coldest month (B), annual precipitation (C), and precipitation of the driest quarter (D) predicted to occur by 2050. Data for Representative Concentration Pathway 6.0.
Proportion of tree and shrub species presently exceeding their current safety margin for maximum temperature of the warmest month (MTWM; A), minimum temperature of the coldest month (MTCM; C), and precipitation of the driest quarter (PDQ; E) in 164 cities where they are planted. Frequency distribution of mean values of MTWM (B), MTCM (D) and PDQ (F) safety margin of each species (n = 3,129). Red and blue lines indicate the median and 5th/95th percentiles, respectively. A positive safety margin (S > 0) indicates that the species has a climatic tolerance limit that exceeds climatic conditions; whereas a negative value (S < 0) indicates that the species is subject to ‘unsafe’ climatic conditions outside its climatic tolerance limits.
Extended Data Fig. 3 Tree and shrub species at risk of future climate change impacts across the world’s cities.
Proportion of plant species predicted to be at risk of changes in maximum temperature of the warmest month (A), minimum temperature of the coldest month (B), and precipitation of the driest quarter (C) in 164 cities where they are planted. Data for 2050 and Representative Concentration Pathway 6.0.
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Esperon-Rodriguez, M., Tjoelker, M.G., Lenoir, J. et al. Climate change increases global risk to urban forests. Nat. Clim. Chang. 12, 950–955 (2022). https://doi.org/10.1038/s41558-022-01465-8
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