The last ice age covers Canada and Northern United States with ice. It ends about 10,000 years ago. Glacial grinding leaves clay, peat, soil, and sand devoid of earthworms. Latitudes between 45° and 69° lack native earthworms. Starting in the 1600s, European immigrants bring to North America invasive night crawlers among other earthworm species in root balls, soil bulbs or dry ship ballast.
Earthworms (soil engineers) epitomize a keystone species. They redistribute nutrients, mix layers, and create pores in soil. Their lifestyle benefits farm crops. They deposit castings (source of fertilizer). Burrowing depths of six feet and extraction of nutrients from decomposing organic matter enriches garden soil.
Regrettably, earthworm behavior hampers forest renewal. They remove surface organic matter critical to sapling development. Burying nutrients too deep challenges sapling’s ability to reach them. This habitat disfavors poplar, birch, and maple saplings by altering soil composition. Recast soils interfere with roots and fungi symbiosis. Tree roots nourish fungi with sugars, while fungi furnish roots with water and unlocked mineral nutrients. Healthy trees network through root and fungus coordination (wood wide web). Earthworms disrupt forest-ecosystem connectivity.
Arrival of jumping “snake worms” from Asia raises alarm. They possess a voracious appetite and reproduce faster than European cousins. Humans unwittingly disseminate them. Curb earthworm proliferation in forests. Value our forests and reflect on Carl Sagan’s message, “Deep down, at the molecular heart of life, the trees, and we are essentially identical.”