The skies have darkened over Metro Vancouver. It appears that the end is nigh, as the sun itself is choked out by thick clouds… of moths.

D. Gordon E. Robertson / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Okay, not quite. The skies are gray these days because of fire smoke. If you’ve seen a few million too many moths this summer, you aren’t alone. Here’s why you’ve got so many new neighbors all of a sudden!

Following a relatively small outbreak of moths last fall 2019, they’ve returned. This time they brought backup.

According to North Vancouver, an outbreak of Looper Moths is to blame. Not just one type either. Although barely distinguishable from one another, this outbreak includes both the Western Hemlock  Looper and the Phantom Hemlock Looper moths. Lucky us.

After receiving several inquiries from curious residents, the District of North Vancouver first publically addressed the matter in late August, labeling looper moths as a “part of the natural coastal forest system”.The outbreak remains most concentrated around the North Shore, but the looper moths have made their homes all across the Lower Mainland, to New Westminster, Burnaby, and Surrey.

This may seem like just another chapter in the bleak story that is 2020, but it’s perfectly natural. Think back to economics class. Why? Roughly every 10-20 years each species of looper moths; and many of their cousins, go through boom and bust population cycles.  

Unfortunately, this occurrence is inevitable, and we were getting overdue; likely the reason why this year’s boom seems so massive. Interestingly, Metro Vancouver is actually in the second year of this wondrous cycle. Theorizations propose that recent, dry summers likely caused an increase in the edible foliage targetted by looper larvae; this abundance of nutrients was the perfect catalyst to trigger a looper moth population boom.

When Moths Attack

The good thing is, looper moths are pretty much completely harmless to humans. They don’t carry disease, they won’t sting or bite. You might’ve heard about the awful appetite certain moths carry for curtains clothing, and cardboard, but this explosive population is only a terror to trees.

Defoliation has been evident from the North Shore, in areas like Mount Seymour and Lynn Valley, to Coquitlam, and stretching as far as the Sunshine Coast and Thompson-Okanagan. Coniferous forestry across British Columbia is at the most risk. An estimated 2,000 hectares of forest have already been impacted.

The diet of the looper moth consists primarily of western hemlock,(hence the name) spruces, pine, red cedar, and many fir trees. Any associated deciduous trees and shrubbery are also prone to defoliation. Trees that become impacted by these moths and their larvae often change color; turning from green to red or orange. Alternately, they may be completely defoliated; stripped mercilessly by the insect’s feast. Not only does the looper moth eat a lot, but it also eats incredibly quickly. A swarm of looper moths may decimate a coniferous tree in a single season. The reason? Looper moths make no differentiation between live and dead leaves/needles.

Not every tree used as a food source dies. The trees that are most susceptible to these species are simply the oldest, weakest of the bunch. Keeping up to date with tree mortality is still important for ecologists; severely decayed trees present several risks to their surroundings, such as wildfires, erosion, and lowering nearby water quality. However, death and decay lead to new life; as trees rot away, their nutrients enter the soil, where new growth begins to occur. Ecologists typically regard this cyclical process as beneficial to ecosystems, expecting an increased level of biodiversity, and greater evolutionary resistance to swarms akin to this. While evidence supports that British Columbian foresty can handle the worst of the explosion, there’s one wildcard. Climate change.

Stressed Trees

Did you know that trees stress as well? In a warm climate, trees targetted by looper moths, and their larvae become stressed. In turn, becoming easier prey for the looper moths. This creates the possibility of a feedback situation, where trees can’t recover properly; and unequipped for future swarms, will be ravaged more and more thoroughly. Only time and careful examination will help determine whether British Columbian forests are recovering optimally or not.

As fall begins to move closer, temperatures around British Columbia will drop. Luckily, that signal’s the end of the looper moths wrath. For now. Ready for the best part of this whole situation? Experts estimate we’re only in our second year of a three-to-four year life cycle for these winged beasts. Yes, this is potentially just the beginning. Everything depends on the province’s climate. A warm, dry spring in 2021 may be very a telltale sign of more looper moths to come. Fortunately, a wet 2020 summer season means that these trees won’t be stressing hard for water.

Using satellites and aerial imaging, British Columbia has begun to conduct surveys, but exact levels of defoliation likely won’t be known until next year. If the population outbreak continues to sky-rocket, the province has the option of spraying Btk, a pesticide only activated once inside the moth larvae’s stomach. This scenario is highly improbable; BTK is almost exclusively used for woodworking in the Okanagan.

Essentially, there’s not a whole lot that can be done about these pests. Experts agree that patience is key, and environmental factors will kill-off these pests. Starting this month, a noticeable decline in the looper moth population will certainly occur. By October, they should be gone entirely. Until next summer. it all comes down to climate. An unusually cold year may devastate the looper moth population. Or, next summer will be warmer, and this mothpocalypse is just beginning

 Feast Fit for a Feline

D. Gordon E. Robertson / CC BY-SA (https://creativecommons.org/licenses/by-sa/3.0)

Not everyone’s complaining about this population surge. Trying to swat these things out of your bedroom may seem pointless, but it’s very entertaining for your cat. Not to mention fantastic exercise as well. They’ll be busy all week honing their hunting skills while ridding you of looper moths. Win-win! These moths are perfectly edible to the cats as well, judging by the voraciousness with which they pursue. I suppose it’s all just the circle of life.