Evaluating the air quality in the city by observing the trees near your home, this is what the Tela Botanica network offers in Montpellier. A participatory environmental program called Lichens Go!
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They are our green lung in the city. Plane trees, chestnut trees, oaks, maple trees … Trees absorb CO2, regulate heat and are sentinels of the environment. They are of great interest to the botanical observatory created in Montpellier, Botanical Canvas, which brings together researchers and citizens.
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We want to create a community around the tree. Because they are reservoirs of biodiversity in urban areas
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Trees in the city are sentinels of our environment
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© Acer pseudoplatanus Françoise Peyrissat via Tela Botanica
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Lichen, a very special organism that reacts to pollution
As part of the “Near my tree” project, the network is calling on residents. Objective, observe and list the lichens on the trees close to home in town.
Lichen is a mixture of algae and fungus that clings to the trunk and branches.
There is a great diversity of lichens and they are sensitive to pollution
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© Lichen foliacé Lydie Dufeu via TelaBotanica
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The family of different lichens is very large. And they are reactive to pollution. By observing them, valuable information on air quality can be gathered.
Become an urban forest detective
How to proceed ? It’s simple, no need to be an expert in botany. A magnifying glass and a piece of wire mesh are enough! It is necessary to choose 3 trees in line, to apply on the trunk the mesh to delimit the zones and inventory the different lichens present.
Here’s how to survey lichens near you
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© via Tela Botanica
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The Tela Botanica website offers a guide to recognize them, called determination key. It then remains to fill in the data.
“It is a very interesting project for the inhabitants. Between Montpellier and Nîmes, are there notable differences in the level of pollution and its evolution? The survey will help us understand it. The ideal is to participate in the long term, ”says Elodie Masseguin, project coordinator in Montpellier.
The richer the air is in nitrogen dioxide, the less lichens
The first data, analyzed by a group of students from the polytechnic school, show that the diversity in lichens is directly related to the average level of nitrogen dioxide measured in the air.
Nitrogen dioxide, NO2, is produced in particular by vehicle engines. It has toxic effects on our health and causes respiratory problems.
The more NO2, the less our little “alien” fungus grows.
Montpellier is one of the very poor students in terms of action against car pollution, according to a Greenpeace report in December 2019.
So, no doubt: the trees in the city also have a lot to tell us about the air we breathe!
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