The Importance of Trees

Last Wednesday, July 4th, environmentalist David Fletcher came to the library to give a talk called The Enchantment of Trees: From Roots to Canopy. Mr. Fletcher started by pointing out the importance of trees to the environment and to the island of Montreal in particular, explaining that in areas which have a healthy forest canopy, more oxygen is produced, more energy is stored, and temperatures are lowered. Take a look at this temperature map of Cote Saint-Luc and the surrounding neighbourhoods – those white areas are white because they’re cool. And they’re cool because there are lots of trees around:

Heat Map of CSL and Environs

Of course, once we realize how important trees are, what can we do to ensure that our beneficial native species don’t become overrun by invasive transplants? Recognizing threats is the first step.

The Emerald Ash Borer

Emerald Ash Borer

This is an insect which has, in some places, severely reduced the native ash population. This is relevant to us because roughly 25% of the trees on the island of Montreal are ash trees or one kind or another.

This bug, as you’d probably guess from its name, bores into the wood of ash trees and eventually kills the tree from the inside. It is not native to Canada, having come from Asia. According to the Canadian Food Inspection Agency, this insect is responsible for the deaths of millions of trees in Ontario and Michigan.

What you can do: First, don’t move ash wood or branches from one location to another (and, in fact, it is currently prohibited to move ash off the island). If you see one of these beetles, contact Cote Saint-Luc’s Public Works department at 514-485-6868. For more info, see the Canadian Food Inspection Agency’s website here.

Common Buckthorn

Common BuckthornThis species of small tree is native to Europe and was brought to North America as a decorative garden shrub at some point in the 19th century. Its bark and fruit used to be used as a purgative or expectorant, though this is no longer the case due to its violent action and possibly dangerous side effects. It has become an invasive species in parts of North America because it leafs earlier than native species, giving it a competitive advantage. In areas where it is abundant, its dense leaf cover keeps native seedlings from growing. It also possibly gives off a substance that slows the growth of other species.

What you can do: This may sound drastic, but… pull it up! If you notice this shrub in your back yard or garden, it’s very easy to remove it from the ground when the plants are young. You may have to do this for a few years in a row, as the seeds have a high germination rate and can germinate up to three years after they’re dropped.

For more information, check out Tree Canada.

Norway Maple

Norway MapleThis is a species of maple that is native to eastern and central Europe and southwest Asia. It produces a large number of viable seeds and also emits a chemical that inhibits the growth of other species around it. It discourages competitors by throwing lots of shade in areas where it dominates (as well as the thick, suffocating layer of leaves that cover the ground around it in the autumn), and it is eaten less often by herbivores than other species are – yet another advantage. It is very tolerant of shade even as a sapling and has shallow roots, which compete with other species at the ground level. For these reasons, it is considered an invasive species in parts of North America, though it’s still often used in urban plantings and can be found everywhere. It is, however, banned in Massachusetts and New Hampshire and is no longer sold by any nurseries owned by Meijer, Inc. (an American chain based in Michigan).

What you can do: Choose an alternative tree for planting, such as sugar, red, or silver maple (which are all native to this area). Remove any Norway maples in your yard, if possible – they are easy to remove as seedlings or young plants. See Tree Canada for more info.

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