Invasion Of The Earthworms!

Emily from MinuteEarth explains how earthworms, known as nature's gardeners, can negatively impact certain ecosystems. Northern North American forests thrived without worms, as thick leaf layers protected seedlings and prevented competition. European earthworms, introduced in the 1800s, disrupted this balance by consuming leaf layers, altering nutrient distribution, and exposing seedlings. This led to fewer young trees and more invasive plants. Scientists worry that earthworms, along with other factors, could transform these forests into savannas, similar to pre-Ice Age conditions. The long-term effects of this transformation remain uncertain.

Why were the forests of northern North America initially better off without earthworms?

• Earthworms consumed too many tree roots.

• The presence of earthworms increased soil erosion.

• The absence of earthworms allowed leaves to protect young trees.

• Earthworms attracted too many predators.

What was one consequence of European earthworms arriving in North America?

• They reduced the population of deer.

• They caused a decline in tree regeneration.

• They increased the amount of leaf litter.

• They improved the growth of native tree species.

How did the introduction of European earthworms affect the forest ecosystem?

• It improved the soil's ability to retain water.

• It led to the growth of more native plants.

• It caused a decline in grasses and shrubs.

• It facilitated the spread of some invasive species.

What are scientists concerned about regarding the future of northern forests?

• The forests might become deserts.

• The forests will become too dense.

• The forests will have too many earthworms.

• The forests could turn back into savannas.

What historical landscape might the northern forests return to due to earthworm activity?

• A savanna

• A dense rainforest

• A tundra

• A barren desert