Trees play an essential role in the well-being of all of us who live in cities (also our mental health); they give us shade, cool the atmosphere, purify the air and water, provide a habitat for native animals, absorb carbon dioxide and produce the oxygen we breathe, but how long can this continue in the face of the increasingly palpable impacts of climate change on our planet?
Now, an international research team, including a CNRS researcher from the Ecology and Dynamics of Anthropogenic Systems Laboratory at the Jules Verne University of Picardy ( Laboratoire Ecologie et dynamique des systèmes anthropisés, CNRS/Université of Picardy Jules Verne) , have published the first global risk assessment for tree species planted in cities taking into account increased temperatures and decreased annual rainfall due to climate change.
Your data is not at all flattering
The researchers found that 56 to 65 percent of tree species planted in cities are threatened by rising temperatures and decreased rainfall. And this figure could increase by 2050. By mid-century, the number of urban trees threatened by climate change will reach between 68 and 76 percent.
“Climate change threatens the health and survival of urban trees and the many benefits they provide to urban dwellers. Here, we show that 56% and 65% of species in 164 cities in 78 countries currently exceed temperature and precipitation conditions experienced in their geographic range, respectively,” the researchers wrote in their study published in the journal Nature . Climate Change. “ We evaluated 3,129 species of trees and shrubs, using three metrics related to climate vulnerability: exposure, safety margin and risk”.
They conducted impact analyzes using current and projected temperatures and rainfall to make predictions for the years 2050 and 2070. They identified a ‘climate safety margin’ for each species, which establishes its ability to tolerate changes in mean annual temperature (MAT). and the annual precipitation (AP) in your city. Although exceeding that margin does not mean that the tree will disappear, it will affect its health and its performance as a crucial part of the urban ecosystem (both its ability to store carbon, as well as to produce fruits, reduce air pollution or resist droughts). y).
“The risk is projected to be higher in low-latitude cities, such as New Delhi and Singapore, where all urban tree species are vulnerable to climate change. These findings help assess the effects of climate change to ensure the long-term benefits provided by urban forests.”
The study highlights the need for strategies to help urban trees cope with climate change, especially as trees will become increasingly important as natural air conditioners during heat waves. Many trees have already exceeded their climate safety margins.
The authors state that their predictions are likely to be conservative, as they do not take into account the potential effects of population growth, urbanization, and the prevalence of diseases and pests. However, they hope the study results can help prioritize efforts to protect urban plants and secure their associated ecosystem services to make cities livable. This includes selecting and planting more weather-resistant species , as well as those that provide a great deal of cover.
Referencia: Manuel Esperon-Rodriguez, Climate change increases global risk to urban forests, Nature Climate Change (2022). DOI: 10.1038/s41558-022-01465-8. www.nature.com/articles/s41558-022-01465-8