Relative to the short period we inhabit this mortal coil, our habitat and the creatures that share it with each other have evolved together over tens of thousands of years. We may have separated from main land Europe since the last ice age but once the ice had gone and temperatures stabilised we have lived in fairly settled times in terms of climate in the UK.
Over this settled period, plants and animals began to develop a new reliance, or symbiosis, with each other. This in turn signifies and determines what we would then call our eco-system.
So, what’s the issue with non-native trees and plants?
Let’s start with the trees. Native trees will grow where they grow thanks to the soil type and constitution, the orientation, if it’s flat or on a slope, wind cover or the altitude, to name just a few of the variants that determine if a tree will succeed or not. What grows where has been sorted out by mother nature over thousands of years and we now have established colonies of species forming very different woodlands throughout the UK.
This brings us onto the creatures that inhabit these woodlands. As these woodlands have evolved, so have the creatures that live in them. Most of them have adapted to specialise in living off certain types of trees, there is an eco-system that exists around each tree. Whether this be bugs that lay their eggs/larva’s in certain wood or to the birds that then eat them, there is an entire food chain (other than the obvious nuts and seeds produced) that depends on having certain native trees for it to go about its business.
It’s not just food that trees provide to woodland inhabitants, they also provide shelter, homes and nesting sites. Birds are especially choosy about where they nest and with the absence of certain tree species we also see the absence of many bird species.
The final thing that has its equilibrium shifted once non-native trees dominate an area, is the woodland floor. Many of the forest floor plants and animals are in cynic with the annual cycle of our native deciduous trees, the disruption of this can have catastrophic effects on the woodland floor. It is not just the small mammals and the creatures that predate on them that are effected, there are other micro systems effected such as the loss of the early spring flowering bulbs that the pollinators so depend on.
I’m about to contradict and confuse everything I’ve just said by stating, not all non-native species should be on a kill list. Some actually benefit certain areas as a result of how long they have been here and they now play a part in a healthy woodland environment, IF managed. This said, careful thought, research and planning should be undertaken before planting up any areas with new trees to ensure that the maximum is achieved for every aspect behind the planting of any new woodland.
If you are going to do it, you may as well do it right!