Trees in Ottawa– and around the world generally– are facing many threats. Threats include climate change (drought, flooding, increasingly more violent storms, warmer temperatures in some locations and cooler temperatures in others), invasive species such as the Emerald Ash Borer, and tree loss to urban expansion. Pollution is also a concern, including air pollution and acid rain.
Climate change is transforming life on earth, and is a major threat to biodiversity, the environment, and humans. Climate change is a threat to trees for a number of reasons:
- Climate change is causing normally rare, extreme weather events to occur more often, and with greater ferocity. Extreme weather events include hurricanes and storms, which can uproot and topple trees because of their high winds.
- Due to climate change, droughts are becoming more intense, and are occurring for longer periods of time. Droughts cause trees to lose leaves through scorching and wilting. Roots begin to die, and when rain finally does return, the tree cannot take in water. Droughts also make trees more susceptible to disease and pests.
- Climate change is altering the distribution of species, changing where they are able to live. This allows invasive species to invade new areas more quickly, and more often.
Invasive Species and Pests
Invasive species are one of the main threats to biological diversity (biodiversity) on this plant. Invasive species have changed–and are changing–the urban forest in significant ways. Invasive species considered a threat in Ottawa today include the Dog-strangling Vine, and the Emerald Ash Borer (EAB). Dog-strangling Vine is an invasive vine that grows in dense patches, suppressing the growth of native seedlings and saplings.
Dutch Elm Disease was an invasive fungus that, decades ago, decimated the elm tree population across North America and other parts of the world. In Ottawa, Ash trees were planted to replace the elm trees lost. Now, our urban forest is facing significant threat from the Emerald Ash Borer, a green beetle that is decimating ash trees. The EAB kills ash trees (but not mountain ash, which is not actually a type of ash) efficiently, and a tree is likely to die within 2-3 years of an infestation. It estimated that 25% of all trees in Ottawa are some species of ash, and all of these trees will be lost within the next 10 years.
We’re learning lessons from our past: clearly we need to plant a diversity of native trees–and many of them– in order to counteract this loss.
To learn more about the affect of Emerald ash borer on our ash trees: Emerald Ash Borer
Forests and trees are often referred to as the lungs of our planet. Trees take in carbon dioxide–a greenhouse gas that is causing climate change– and convert it to oxygen. Trees also filter air and remove fine particulate matter that is harmful to our health; for example one study estimates that asthma rates in young people dropped by 25% for every 343 trees found in a square kilometer. Despite the good work trees do cleaning and filtering polluted air, air pollution is also a threat to trees. Heavy pollution can cause particulate matter to accumulate on leaves, which can impair photosynthesis and negatively affect tree growth.
The major sources of air pollution is emissions from power generation and transportation, and these emissions also create acidifying particles, which cause acid rain. Acid rain weakens trees and makes them more prone to disease and pests. Acid rain can also leach nutrients from the soil, and release toxic metals that are harmful to tree growth.
Pollution from urban runoff is also a problem for urban trees. Urban runoff is the rainwater that collects on and washes off of the surface of urban landscapes, such as pavement (roads, parking lots, sidewalks), urban green areas (lawns, golf courses, parks), and buildings. This runoff water often contains contaminants and pollutants that are harmful to trees, such as motor oil, gas, heavy metals, pesticides and fertilizer from green spaces.
Learn more about how Ecology Ottawa is doing their part to help keep our rivers clean: Ottawa River Acton Plan
Urbanization is a significant cause of tree loss. As cities expand, trees are often among the first casualties. Trees are cleared to build roads or to widen existing roads and highways, to create parking lots and new buildings, and for golf courses, stadiums, and other types of development.
As we clear trees for urban development, we also lose the diversity of birds, mammals, invertebrates (insects, worms, and other creepy-crawlies), plants, fungi, and lichens that are associated with these trees. This diversity of life–biodiversity–is essential for maintaining ecosystem health. Ecosystems that are healthy and functioning provide us with many ecological goods and services, such as clean air, fresh water, pollination of crops in our gardens and of trees that bear fruit, etc. Healthy ecosystems also provide us with places–such as parks and walking trails–that give us joy and pleasure to spend time in, alleviating stresses that arise from day to day life.
Greening our cities, by planting native trees, is necessary for our mental and physical well-being, and for increasing biodiversity. So let’s get out there and plant some trees!
To learn more about how Ecology Ottawa’s Complete Streets campaign: Complete Streets
Doing Your Part
There are many steps we can take to help minimize how our actions contribute to these threats.
Climate change and air pollution: in many ways, these two go hand in hand. The major sources of air pollution is emissions from power generation and transportation, which are also some of the main sources of green house gas emissions. By making simple changes, we can reduce the amount of green house gas and air polluting emissions that we produce.
- walk, take public transit, or cycle instead of driving your car
- turn off electronics and lights when not in use
- use energy-efficient appliances and devices
- don’t use pesticides or fertlizers on your lawn (as they contribute to water pollution)
- consider using an alternative to salt (eg: sand) to increase traction along your walkways and driveways in the winter, or use only the minimum amount of salt needed to get the job done (also a contribuer to water pollution)
Emerald Ash Borer: it is prohibited by law to move ash tree material and any kind of firewood from one location to another in many areas of Ontario and Quebec. This regulation is in place to slow the spread of the Emerald Ash Borer. If you are camping, and you do not use up all of your firewood, leave it behind. Do not pack it up to take home, or to your next camp-site. Violation of this regulation will result in fines and/or prosecution.