I have a huge (verging on unhealthy) appreciation for earthworms that I mistakenly assume all of my friends share. Yesterday I was caught in a Youtube vortex that began with watershed education and ended with the mythical giant worms of southern Australia that stretch eight feet in length. Though most people generally understand that earthworms are important to healthy soil, their presence is not necessary for every ecosystem.
Healthy boreal forests do not naturally contain earthworms, but non-native worms are so often introduced to these areas that they are commonly overlooked as an invasive species. Healthy forests contain clear subterranean levels between soil and organic matter. Each level contains unique nutrients and host a similarly unique variety of bacterial organisms.
When earthworms are present, these levels within soil become blurred. Worm activity causes chemical reactions that shift the nutrient dynamics beneath the leaf litter, causing keystone forest plants to struggle or fail altogether. Worms also eat through the roots just below the soil’s surface, making it very difficult for important grasses to survive as the soil pH changes. As the balance between organic and inorganic decomposition shifts, the invertebrates inhabiting the soil die and can fail to repopulate. This population change causes forest floor plants to die off, and leaves the area vulnerable to invasive plant species.
As worms consume dead roots, leaves, grasses, manure, and soil, their digestive system concentrates the organic material in the food they eat. Worm excrement is far richer in available nutrients than the surrounding soil, and their extended presence can transform soil composition. This increases the nitrogen and other essential minerals that plants are able to access. The corpses of deceased earthworms also decompose very rapidly and add to nitrogen content of soil. While this resulting rich soil is desireable in man-made gardens, boreal forests do not require nutrient-dense soil. These increased nutrients lead to increasing populations of small plants and shrubs along the forest floor, but fail to support larger vegetation.
Healthy boreal forests in their true form survive with very low nutrient levels in their soils. Pines thrive in sandy soils, and other species are similarly adapted. These healthy forests lack brush and small plants along their forest floor and remain dominated by boreal tree species. As earthworm populations invade a boreal forest, brush begins to grow and alter the natural ecology of the forest. This phenomenon is so common throughout North America that these forests are domestically considered to be “healthy” boreal forests. In reality, earthworm-infested areas of boreal forest are more prone to erosion, species failures, soil degradation, and collapse.
I have watched this video over a dozen time and it still makes my day. This woman loves worms so much, her excitement is contagious: https://www.youtube.com/watch?v=9ZHTerOJYMA
I also used this article as a point of reference to reinforce my scientific knowledge: http://www.sciencedaily.com/releases/2015/04/150422104041.htm
Although this does not relate directly to my post, I find leech worms fascinating. I discovered this video last Christmas and proceeded to show everyone I know. Try to get past the creepy and focus on what amazing creatures these are: https://www.youtube.com/watch?v=0fGGz6d3vC4