Cities around the world are increasingly relying on trees as a tool for cooling and adapting to climate change. Tree canopy cover is a common metric used in planning and investing in green spaces. New study however, it shows that It is not only the presence of trees that is important, but also their health and functionality..

Researchers from the University of Minnesota focused on the Minneapolis-St. Paul (MSP) metropolitan area and used data from the ECOSTRESS satellite and machine learning methods to examine how the health and function of urban trees vary depending on the environment in which they grow.

They found that The temperature of treetops varies depending on locationCooler crowns, indicating better health and function, were found in less urbanized areas and near bodies of water and parks. Conversely, in densely built-up areas with high population density and heavy traffic, trees had higher crown temperatures, indicating poorer health.

The study also introduced a new index, Combined Urban Tree Index (CUTI), which takes into account not only canopy cover but also canopy temperature. CUTI helps identify areas where trees provide the greatest benefit and enables more efficient planning of planting and maintenance of greenery.

The findings suggest that The benefits of urban trees are not evenly distributedAreas with higher canopy cover tend to be cooler, wealthier, and more white. This inequality reflects historical policies and practices that have led to segregation and uneven distribution of green space in cities.

A new study highlights that When planning the planting and care of urban trees, it is necessary to take into account not only their number, but also their health and functionality.Focusing on the quality and location of green spaces can lead to a more equitable distribution of benefits and increase the resilience of the urban environment to climate change.

Research results can help cities invest more effectively in greenery and focus on areas where trees can bring the greatest benefitFurthermore, considering the health and function of trees can lead to the selection of more suitable species and better care for them, ultimately contributing to a healthier and more sustainable urban environment. Spring

Article published in AGU Advances

Jean V. Wilkening, Xue Feng

Glossary

• Urban Heat Island (UHI): A phenomenon in which urban areas experience significantly higher air temperatures than their surrounding rural areas.
• Transpiration: The process by which a plant releases water into the atmosphere from its leaves.
• Canopy Temperature: Upper leaf temperature in tree crowns, used in this study as a proxy for tree health and function.
• ECO STRESS: A NASA mission focused on measuring evapotranspiration from the International Space Station, providing data with high spatial and temporal resolution.
• LST (Land Surface Temperature): Earth's surface temperature, measured using remote sensing.
• Random Forest (RF): A machine learning algorithm used for classification and regression. In this study, it is used to model the relationship between crown temperature and built environment characteristics.
• SHAP (SHapley Additive Explanations): A method for explaining machine learning model predictions that assigns each feature a SHAP value that measures its contribution to the prediction.
• Impervious Fraction: The proportion of the Earth's surface that is not penetrated by water, such as roads, buildings, and sidewalks.
• Topographic Wetness Index (TWI): An index that quantifies the influence of topography on water accumulation in a given location.
• Combined Urban Tree Index (CUTI): A new index developed by the study authors that combines tree cover and canopy temperature to estimate the benefits of trees in urban environments.
• ΔFEELING: The change in the CUTI index that occurs after an increase in tree cover.