Why we need urban forests


Words by: James Godfrey-Faussett
— Lead Forest Maker at SUGi

It’s remarkable to think how trees and urban trees in particular have evolved to deal with pollution and even look for the potential locked away within the makeup of the pollutants.

Trees orientate the leaves of their canopy to maximize the potential for this and the more Co2 in the atmosphere the busier they are.

Carbon dioxide, that we think of as a toxic gas, is the building block trees seek out. Splitting the carbon and oxygen atoms via photosynthesis and then using the carbon to build their bodies and feed the below ground biology they work in unisom with.

It is remarkable to think a carbon atom from a car exhaust can that same day be processed by a tree as fuel to feed microscopic organisms living with the tree’s roots.

Trees also comb pollution out of the air using the millions of tiny hairs found on their leaves. The tiny tree ‘leaf combs’ capture the minute particles of pollution. As the leaves tend to be waxy, when it rains the pollution is easily washed off in solution. It then makes its way down the trunk to the soil where the chemical and physical structure of the soil separates the pollution and the rainwater.

This is where the real magic starts - underground in the metropolis of fungi and bacteria that work in harmony with the fine tree roots.

The microscopic biology of the soil works like busy bees with their array of enzymes to split apart and rejoin the structure of the pollutants coming their way. They literally take the pollutants, break the chemical bonds and release the atoms - for example deadly No2 can become nitrogen and oxygen atoms.

The soil mycorrhizal fungi as well as bacteria need sugars produced by the tree and the tree needs the recycled minerals from the pollution reworked by the microbes. The mycorrhiza use the sugars as energy to retool the enzymes for minerals and metals needed by the trees. This allows the trees to grow a better canopy and root systems, which helps the mycorrhiza to multiply and everyone benefits.

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