A recently published study in Ecological applications details how trees in New York City and Boston are more affected by heat waves and drought than trees of the same species in nearby rural forests. The discovery, made by researchers at the Advanced Science Research Center at the CUNY Graduate Center (CUNY ASRC), highlights the challenges facing urban trees in the context of climate change and underscores the importance of tailored urban forestry as a tool to protect tree species and reduce urban heat islands.

The research is timely, given the record-breaking rise in global average temperatures and the current hottest summer on record. As cities continue to grapple with the impacts of climate change, this study provides important insights into how the health of urban trees and the ecosystem services they provide could be at risk.

Key findings:

• Urban trees in New York and Boston are more affected by heat waves and drought than rural trees.
• In extreme weather conditions, the growth and carbon storage capacity of urban trees decrease significantly.
• The authors suggest that the harsh urban environment, characterized by hotter, drier conditions and higher levels of pollution, increases the vulnerability of urban trees to climate stress.

For their study, the researchers used tree cores from urban and rural forests to reconstruct historical growth rates and then compare them with climate data. The goal was to find out whether urban trees are more affected by climate stress than their rural counterparts. The study found that urban trees suffer more during heatwaves and droughts, raising doubts about their long-term health and ability to provide important ecosystem services.

“Trees are an essential component of urban sustainability and climate resilience strategies, providing benefits such as temperature reduction, stormwater management, recreational spaces, biodiversity support, and improved human health,” said study lead researcher Andrew Reinmann, professor in the Environmental Science Initiative at CUNY ASRC and the Department of Geography and Environmental Science at Hunter College. “Understanding why urban trees are more sensitive to climate stress is the next step in enabling urban planners, forest managers, community groups, and policymakers to develop effective urban forestry plans.”

Such plans could include developing new management protocols to maximize the size of planting pits and select tree species better adapted to urban conditions.