Maintaining our urban forests

Written by Peterborough Green-Up staff

While we usually think of forests and cities as two very different places, trees have a huge effect on how well cities function, and on the health and well-being of the people who live there. In fact, the trees in our cities are an “urban forest,” whose true worth we’re just beginning to understand and value.

Consider an aerial view of your city or town in the summer. When you look down from a bird’s eye view, the tree canopy covers much of what you see. The canopy is made up of islands of green leaves and branches that cover the streets, buildings and parkland.

With greater understanding of the benefits of urban trees, many cities are setting targets of 40 per cent for their total tree canopy coverage, as recommended by American Forests.

As our cities expand, we are losing more and more of our surrounding natural forests, and replanting is not keeping up with annual losses. We are losing urban forest cover at a time when we need the benefits it provides more than ever. It’s time to think of trees as essential to our health and welfare, not just optional landscaping.

Protecting and enhancing our urban forest is a community affair, requiring plenty of team work and advance planning. The first step is understanding the many benefits of trees in the city, and what it takes for individual trees to thrive in the urban landscape.

It’s Tough to be a Tree in the City

Although trees provide so many benefits for city-dwellers, including cleaning the air,creating oxygen, reducing storm water runoff, and helping to conserve energy, urban stresses make it difficult for trees to survive and thrive.

Lack of water, compacted and nutrient poor soil, pests and disease, road salt and air pollution, restricted root zones, and mechanical injury are a few of the challenges facing trees in the city.
 
With all the stresses of city life, the average life expectancy of a newly planted urban tree is only 10 to15 years. With a little attention and careful planning, we can help our trees live long, productive lives.
 
Maintain the Old

Larger mature trees provide more overall benefits than small trees. This means our first priority is taking good care of existing trees to help them thrive. A few tips for good maintenance include: top-dressing the root zone with leaf compost every year (1 to 2 cm, 1/2” depth), watering deeply during periods of drought, mulching fallen leaves with a mower in autumn, properly pruning damaged branches and protecting the trunk and root zone from damage. Keep mulches and compost away from the trunk.

Encourage and Diversify the Young

Have a look around your yard and neighbourhood. Are there many kinds of trees, or are they mostly the same species? Look for good plantable spaces in your area, and work with your neighbours to boost the diversity of your urban forest. Young trees need extra attention – make sure they’re thoroughly watered once a week during dry periods. Did you know that young trees can grow twice as quickly if their root zones are mulched with woodchips instead of letting grass grow around the trunk? Remove all stakes and guy wires around young trees after one year, and protect tender tree bark from damage by installing and maintaining tree guards.

Become a Volunteer Urban Forester

There are many ways to help create a healthy urban forest. Caring for the trees on your own property is one way to begin, but there are many other opportunities to consider. Helping with neighbourhood tree inventories, planting and maintenance programs, training workshops or public education events are some of the ways you can get involved.


This article was written by staff of Peterborough Green-Up's Urban Forestry program, in Peterborough, Ontario. This program sees volunteers taking inventories of Peterborough's trees, assessing their health, and encouraging greater community participation in maintaining this "urban forest." You can learn more about Green-Up’s program by visiting http://www.urbanforest.greenup.on.ca.