New neighbours move in and immediately cut down a magnificent silver birch and create a drive with non-porous material. I am mad! I love trees, writes Fran Hamilton.
What’s all the fuss about?
Let’s start at the bottom, below the surface of the soil. Maybe you have noticed white threads on old rotting wood. These are called mycorrhizal fungi and absorb nutrients and minerals in the soil and transport them from one plant or tree to another, often over huge areas. In this way they extend the roots of any plant. Nearly all plants (including vegetables) are dependent on mycorrhizal fungi for their thriving and survival. You can read about the astonishing abilities of underground fungal networks in Merlin Sheldrake’s book ‘Entangled Life’.
Still at ground level, trees absorb water and hold it, thus regulating the flow that any heavy rain brings. Once a tree has been removed, soil erosion can result from the removal of the many roots that anchored it in the soil.
Above the ground, the water the trees have absorbed is drawn up and eventually expelled via the branches and leaves. This cools the air, which brings increasing benefits as extreme weather becomes the norm due to climate change. One large oak tree is capable of transpiring 40,000 gallons of water into the atmosphere each year. Strategically planted deciduous trees can cool a building in the hotter months, and then allow the warming sun into our homes during the winter months. Trees can also protect buildings from the wind.
Another key benefit of trees is the reduction in pollutants as a result of the leaves absorbing particles. Researchers from the US Forest Service have calculated that trees in the US remove over 17 million tonnes of air pollution each year, saving at least 850 lives that would otherwise be lost through acute respiratory illness. No doubt the UK will also have a high figure.
Trees are also a vital habitat for wildlife. Tree cavities provide nest and roost sites for birds and bats. In Europe, an estimated 30% of forest-dwelling birds use tree cavities, and it is well known that the availability of cavities – in number and type – is a limiting factor of bird-population size. We quietly acknowledge the lack of tree cavities in our landscape every time we put up a nest or bat-box. The research, however, is starting to suggest that these boxes are not adequate replacements for natural hollows and cavities. Trees have more stable microclimates than boxes, buffering against temperature fluctuations.
Even a dead tree is valuable for wildlife. Springtails, mites, beetles, flies and parasitoid wasps are particularly likely to use dead trees, but it isn’t unusual to find the humble earthworm living metres-high in a tree cavity.
So besides not cutting down a perfectly healthy tree what can we do? Tree cover in Devon is only 11.8% – slightly less than the national average. Surprisingly, Camden and Croydon feature among the top 20 places in England and Wales with the most tree cover, while largely rural areas like the Lake District and the Yorkshire Dales have the least.
But before rushing out to plant a tree it’s worth doing some research on which tree to plant. You need the right tree in the right place. Getting it wrong can do more harm than good. The Woodland Trust has lots of information on its website, including an A-Z of British trees and a tree ID app, plus tips on how to choose a tree and where to plant it.
Planting trees is often promoted as a way of offsetting our carbon emissions, but such schemes can be little more than greenwash. In many cases the trees would have been planted anyway. Reducing emissions in the first place is always the better option.
So be alert to the sound of the chainsaw; trees are really precious and need all the help we can give them for all our sakes.