Fire and insects
Glacier National Park
Fire and insects play an essential role in forest health. These natural disturbances can open up the forest canopy by thinning out older, less healthy trees. This encourages new growth and results in greater biodiversity. Disturbance by fire and insects also improves forest resilience by creating a patchwork forest of varying ages. This patchwork creates natural barriers to large, severe wildfires or insect outbreaks. In a national park, these processes are expected; however, if they pose a risk to public safety, Parks Canada will take action.
Many Indigenous cultures understood the importance of fire as a natural process. This view was not shared by European and other settlers founding permanent communities in the west. For over 100 years, the priority in Mount Revelstoke and Glacier national parks and surrounding areas was to put out wildfires.
To restore natural fire cycles, fire management specialists need to understand the historic fire regime of the area. The fire regime describes fire patterns, like frequency and size, over long periods of time. For the area including Mount Revelstoke and Glacier national parks, the fire regime is described as having infrequent stand replacing fires, or fires where all the overstory trees are killed, and random small wildfires, almost all caused by lightning strikes. Being in the Interior Wet Belt, characterized by significant precipitation, both as rain and snow, it is not surprising that large fires were infrequent. Fire suppression has still had an effect on these forests, leaving them more vulnerable to disease, insect outbreaks and severe wildfires.
Outbreaks of naturally occurring forest insects are the main source of disturbance in the interior rainforest. Insects will typically infect older, larger diameter trees. This helps open up the canopy, allow sun to reach the forest floor and encourage new growth. While insects play a natural role in the forest ecosystems, factors like wildfire suppression and climate change can result in more damaging outbreaks. Parks Canada monitors forest insect activity on an annual basis. Parks Canada may intervene in a number of ways if an outbreak poses concerns for visitor safety, is resulting in increased wildfire risks, or has the potential to impact neighbouring lands. Some examples of intervention used by Parks Canada include hazard tree removal and prescribed fire. To protect healthy whitebark pine trees, a species at risk, from pine beetle, Parks Canada has also used anti-aggregation pheromones. In the form of patches attached to trees, the pheromones mimic the scent used by pine beetle to let other beetles know that the tree is already occupied.
Spruce beetles are bark beetles that are native to British Columbia. They play a key role in the rainforest ecosystem of the Columbia Mountains. Spruce beetles typically infest downed or weakened trees. In large infestations they can also infect healthy trees, particularly in mature or over-mature forests.
Spruce beetles are tiny with adults averaging around ½ cm in length. The beetles will bore into a tree and lay 3 -4 groups of around 100 eggs. The hatched larvae then feed on the tree's phloem, the plant tissue that brings food from the leaves to the rest of the tree. The adults can also infect the tree with blue stain fungus, which blocks the flow of water within the tree. Between the beetle larvae and the fungus, the tree can no longer get food and water, and will die.
A recent large outbreak in Glacier National Park has left thousands of spruce trees dead or dying in and around Rogers Pass. The area includes several campgrounds, day use areas, visitor and operational facilities, as well as cultural resources. Beetle-killed trees can increase the risk of natural blow-down. In public use areas this affects visitor safety and can increase the risk of damage to park assets and infrastructure. Large outbreaks like this can also increase the risk of wildfire in affected areas by adding to the fuel load. To reduce the public safety risk and ensure that these facilities can remain open, large-scale hazard tree removal is taking place. Once this work is complete, regular annual hazard tree assessment and management at visitor areas will continue.
Hemlock looper are moths native to British Columbia. Looper outbreaks are a natural forest process. The larvae feed primarily on western hemlock and western red cedar needles. Looper larvae hatch from eggs in the spring and feed on both new and old foliage. The bigger they get, the more they eat, chewing off needles at their bases. Trees will become noticeably bare, starting with the upper crown. In heavy infestations, trees may be stripped in a single season. The more a tree is defoliated, the more likely it will die.
Late in summer, larvae are very mobile, crawling over tree trunks and shrubs, and dropping by silken threads from the trees to the ground.
Outbreaks tend to occur in 20-year cycles with each outbreak lasting around 3 years. The most noticeable sign of an outbreak is the presence of large numbers of moths in late summer. By fall, the ground may be littered with parts of needles and thousands of dead moths.
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