Every time you exhale, you emit carbon dioxide - a gas that is partly responsible for climate change. However, humans and animals need oxygen to breathe in. And that is produced by plants. An old, healthy tree about 20 metres high provides around 10,000 litres of oxygen a day - enough air for up to ten people to breathe.

The "green lung": CO₂ storage tree

Wondering how a tree makes oxygen? Trees carry out photosynthesis in order to grow. To do this, they absorb carbon dioxide from the air. The process works as follows: With the help of sunlight, they break down the gas into its components and transform it into materials they need to form wood. For one cubic metre of wood, a tree absorbs an average of one tonne of CO₂. The by-product of photosynthesis is oxygen. Besides factors such as size and age, the type of tree is also relevant: A beech or chestnut absorbs about twice as much CO₂ as a spruce.

Via leaves or needles, trees can also filter dust and particles that are in the air. Annually, the mass per tree amounts to up to 100 kilograms. If it rains, the dust runs off along the trunk and directly into the ground. 

Summers are getting warmer and warmer - trees act like air conditioners

It is early summer and the first heat wave is rolling in: The heat doesn't spread, but increasingly clogs up the streets of the inner cities. This is the moment when you like to sit under the broad canopy of trees? That's probably because even in overheated cities they not only provide excellent shade, but cool air: A single tree evaporates up to 500 litres of water a day. As a result, a microclimate is created directly beneath it and the temperature difference of several degrees can be clearly felt here. The evaporation extracts so much heat from the surroundings that one could compare the cooling capacity with that of about ten air conditioners. The temperature near the green giants can then feel up to 15 degrees colder. This could help in the future, because experts expect dry summers with extreme heat and periods of drought to become normal in the future.

Reforestation: Trees in the fight against climate change

No one can say across the board which tree absorbs the most CO₂. The CO₂ absorption rate depends on factors such as location, soil quality, water supply, prevailing climate as well as the age, height, diameter and wood density of the tree. And a single tree alone is not enough to regulate the problem of heat and CO₂ emissions. So to fight the climate crisis, we need to plant even more forests. By the way, a mixed forest can store more carbon than a forest that consists only of a monoculture. In addition, they offer more resistance to environmental influences such as storms or pests.

Despite the great power of trees and forests, they alone cannot completely remove the amount of CO₂ from our atmosphere. Rather, they shift the tipping points in our climate system into the future. In order to reduce the consequences of climate change even more radically, measures such as reducing emissions, for example by abandoning fossil fuels, are definitely necessary.