So while skimming through the news the other day, a headline about an earthworm invasion caught my attention. Personally I thought earthworms were common and existed pretty much anywhere, but once I read the article about invasive earthworms being found in the Yukon and Northwest Territories I decided to look into it a little more. It turns out that the Territories had been earthworm free since before the last ice age, but only now are they appearing in the forests.
Recent studies have shown in Ontario and British Columbia, that since many native earthworms did not survive the last ice age, a lot of earthworms found have been introduced into the forests (Addison 2009). The introduction comes from different methods, such as fishermen using worms as bait or farmers using worms to help with their crops. The problem the worms cause is through changes in the soil such as phosphorous levels, pH levels, and nitrogen cycling within the forest environment (Addison 2009).
Currently the long term impacts of what effects the worms will have are unknown as they are just appearing. In areas such as Quebec, earthworm invasions have caused a decline in maple stands, due to changes in the phosphorous levels in the ground (Frelich et al. 2006). Since the effects can be seen in the lower areas of Canada, the effects on the earthworm free forests are unknown and cannot be estimated. The only information comes from looking at other parts of North America which have been affected and seeing problems in states such as Minnesota, whose boreal forests have some resemblance to Northern Canada and seeing how introduced earthworms are putting native plant species at risk of going extinct (Frelich et al. 2006).
The best thing that is going for the northern forests is that some of the introduced earthworms cannot withstand cold temperatures (Sanderson et al. 2012). The problems they do cause though are also disruption of the fine root biomass of the native plant species decreasing their fitness resulting in less healthy plants. The plants that do survive are only those that can adapt to the changing environments or invasive plants that came from same climates as the earthworms (Sanderson et al. 2012).
In the long run not a lot is currently known about how the earthworms will truly affect the forests in territories, though research is beginning to happen as ecologists are noticing changes in southern areas and making efforts to protect the northern areas (CBC). The research that has started in the north starts with searching for worms near roadways, campgrounds, and boat launches and has turned into a public outreach as well. The public outreach started from University of Alberta researchers whom followed the worms north, and to increase chances of finding the many different species other than verbal outreach they have also created Worm Tracking apps for phones for the public to mark on maps where they saw the worms.
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Frelich, L. E., Hale, C. M., Scheu, S., Holdsworth, A. R., Heneghan, L., Bohlen, P. J., and Reich, P. B. 2006. Earthworm invasion into previously earthworm free temperate and boreal forests. Biological Invasions. 8(6):1235-1245.