UFMP Information Bulletin #2: How are Urban Forests threatened?

What are threats that impact urban trees?

Urban trees are trees that are located in settlement areas. There are many different and similar challenges these trees face in comparison to those in natural forests. There are two overarching threats to urban trees:

• Environmental Threats, including the effects of climate change; and,

• Man-Made Threats.

How do the urban environmental conditions impact urban trees?

The environment in natural settings is much different than that of urban ones. The threats posed to trees in settlement areas are heightened, including:

• Invasive species, such as the Emerald Ash Borer, can weaken and/or kill urban trees en masse;

• Urban environments are hotter and fluctuate more than in rural forests. Those fluctuations, urban heat waves, and droughts result in less conducive growing conditions;

• Urban soils may be poor due to chemical contamination, such as road salt, too much fertilizer, and herbicides; and,

• The effect of climate change, including the effects of extreme weather events, are most acutely experienced in urban environments.

What man-made threats exist for urban trees?

Urban trees that grow with us are affected by the everyday actions we take and the things we build. These threats include:

• Development can cause urban forests to become fragmented which diminishes their rate of growth, biodiversity, and ecological function potential;

• Materials used in infrastructure can cause an increased soil pH and affect soil quality;

• Underground pipes, buildings, and roads all cause urban trees diminish the amount of potential growing space underground for roots;

• Intensive urbanization can cause accelerated erosion of valleys, streams, and forest soils due to increased runoff; and,

• Damaged trees as a result of people harmfully using urban forests. Uses like campfires, motorized vehicles, and walking in protected areas alters the forests and transports new invasive species.

These factors result in stunted growth and fewer trees reaching maturity.

What can residents do to mitigate these threats on their property?

• Plant trees in open areas with enough space between the tree and any structures;

• Wait at least 24 months between pruning trees;

• Never remove more than 10%-20% of the trees crown when pruning;

• To limit negative salt, fertilizer, and spray impacts, consider how much product is absolutely necessary.

• Avoid chemical methods of removing trees; and,

• Attempt to disturb the natural environment around urban trees as little as possible when enjoying the Town’s parks and forests.