Author: David Salcines
In a world increasingly affected by climate change, cities are seeking strategies to protect the health of their inhabitants and reduce environmental risks. Among the most effective solutions are green infrastructures, with urban trees being an important part of these initiatives. Trees not only provide shade, which helps mitigate the effects of heat waves they also promote rainwater infiltration reducing the risk of flooding during intense storms and they improve air quality by absorbing pollutants and in this way contributing to a healthier urban environment.
Despite the many benefits that trees bring to cities, there is a serious problem that often goes unnoticed: climate change is severely affecting the health and safety of these same trees. A recent study, which analysed more than 3.000 tree species in 164 cities around the world, reveals that many of the species that currently are used in our cities are already living in climatic conditions that are outside the range of conditions to which they are naturally adapted. Globally, more than half of the species studied are being subjected to temperatures or precipitation levels that do not correspond to those of their original natural habitat and this situation is expected to worsen by 2050, with up to two out of three urban tree species projected to be at risk due to warming and changes in precipitation.
The problem is exacerbated because many of the species currently planted have a very narrow climate safety margin meaning that with a small increase in temperature or a slight reduction in rainfall, they quickly reach the limit of what they can physiologically tolerate. This chronic climate stress not only weakens the overall health of trees making them more prone to disease and pests, it also makes them more vulnerable to other hazards, such strong winds. A healthy tree that is well adapted to its environment is usually more resistant to inclement weather, but a tree weakened by heat or lack of water is more likely to suffer damage, such as large branches falling or the trunk toppling over completely, posing a serious danger to people, vehicles and infrastructure.
Traditional risk management in urban green spaces has been based on preventing these incidents through preventive pruning or replacement of trees before they become dangerous. But this task is becoming more complicated as the frequency and intensity of extreme weather events such as strong winds are increasing as a direct consequence of climate change. In Europe, for example, regions like Mediterranean coast and the Italian peninsula are particularly prone to these events, experiencing between 40 and 60 days of storms per year on average.
This reveals a critical gap in urban planning, it is not enough to plant more trees, we also must plant the right trees and manage them more intelligently, this involves:
- Selecting species for the future climate: urban planners and foresters must begin to take climate projections into account to choose trees that can thrive in the changing conditions that will prevail in the coming decades.
- Diversifying selected species: relying on a handful of preferred species limits the adaptability of urban green spaces. By having a variety of species limits the impact of pests and diseases ensuring that the urban ecosystem continues to function healthily.
- Tree health monitoring: tree health assessment systems are needed to diagnose the vitality of existing trees, quickly identifying those that begin to show signs of stress from heat, drought or disease. This monitoring is the basis for establishing a truly effective early warning system that allows managers to act in time.
It is in this context that the TREESURE project seeks to provide a response to address these challenges by developing a decision support system that combines nature based solutions with satellite data and IoT sensors installed on trees to continuously assess and manage the risk of tree failure or fall in real time.
The initiative aims to implement a collaborative approach designed to improve coordination and communication between all actors involved in disaster management. In addition, the project highlights the importance of clear communication with the public, especially when it comes to potentially unpopular decisions, such as preventive felling. Building trust and explaining the reasons behind actions is essential to avoid social rejection and ensure the long-term success of tree risk management strategies, ensuring that our urban forests remain safe and resilient allies in the fight against climate change.
Sources:
Climate change increases global risk to urban forests | Nature Climate Change
Urban adaptation in Europe | Publications | European Environment Agency (EEA)