Trees are essential parts of our landscape. We cherish them for the beauty they give to our gardens and cities and the way they filter and clean the air we breathe and bring the temperature down a few degrees in the heat of the summer. Just seeing them has been shown to make people feel better and relax, lowering heart rates and reducing stress.
And trees are long-term investments. Some can live 1,000 years or more … but very few do.
City trees, which have to battle pollution, poor soil, poor drainage, insufficient soil volume, salt buildup, branches ripped off by tall trucks, slamming car doors and vandalism, to mention just a few inhibiting factors, have an average lifespan of only about 15 years according to one study, although another allows them 25 years.
The outlook for trees grown in home gardens and parks is much better: more or less 100 years for maples and beeches and 75 years for most oaks and spruces. Even naturally short-lived species, like paper birch and mountain ash, ought to be good for about 25 to 30 years.
However, no tree lives forever. Many begin to decline as they reach the limits of their average lifespan: major branches die back and aren’t replaced, wounds no longer heal well, the trunk becomes hollow, etc. Desperate homeowners can sink a fortune into trying to keep a dying tree alive: insecticide or fungicide treatments, careful pruning, props, fertilizations, watering, etc. and yet they often continue to decline.
And trees sometimes die or decline well before they should. Just like some people die young, so do some trees. That’s just life! They could be infected by a disease, have been hit by lightning, suffer root damage due to vehicles parked on their root system, etc., but most often, there is no clear explanation.
Essentially, when you plant a tree, your hope and expectation is that it will live and thrive as long as you inhabit your home, but sometimes it simply doesn’t. And when you buy an older home with older trees, the chances of gradually losing some of them increase.
Now That It’s Dying
When a tree is dead or in serious decline, the first reaction of most homeowners is to have it removed. That’s a wise and legitimate decision if there is any danger the tree could hurt people or cause damage to property when it falls. Also when it carries a disease or insect that could spread to and kill surrounding trees (Dutch elm disease, emerald ash borer, etc.).
But what about an older tree gradually declining in the far corner of your yard, well back from the house or parked cars, or in a forested area?
Declining, dying or dead trees (snags) are a vital part of any thriving ecosystem. One third of all woodland birds nest in holes or cavities in dead trees, including woodpeckers, owls, and wood ducks. Bats (already severely threatened in many areas), flying squirrels, raccoons and many other mammals also depend on them. Birds of prey use them as lookouts and food handling points.
A host of insects and mushrooms feed on dead wood, sight unseen … and they in turn feed birds and mammals.
Even when a dead tree falls, it contributes to the environment. As it crashes down, tearing limbs off neighboring trees, crushing smaller ones, it opens a light gap in the forest, allowing understory trees to grow and thus the the forest can renew itself. The trunk, if left to lie where it falls, slowly decomposes, feeding and hosting a wide range of animals and fungus of all sorts when it does. Plants and mosses grow on the fallen tree and some trees species even sprout there before going on to become forest giants in their turn.
Wherever possible, the ecological thing to do is leave dying and dead trees standing. And even when they fall, do move the trunk off a path or road, of course, but try to leave it nearby to gradually rot away and enrich the soil.
Where possible (again, I repeat that there are places where you can’t legitimately leave a dead tree standing), just leave the tree to die gracefully … but do think of planting a replacement!
Trees are always wanted, dead or alive!