Earthworm
Environmental impacts

The major benefits of earthworm activities to soil fertility for agriculture can be summarized as:

Earthworms accelerate nutrient cycling in the soil-plant system through fragmentation & mixing of plant debris – physical grinding & chemical digestion. The earthworm's existence cannot be taken for granted. Dr. W. E. Shewell-Cooper observed "tremendous numerical differences between adjacent gardens", and worm populations are affected by a host of environmental factors, many of which can be influenced by good management practices on the part of the gardener or farmer.

Darwin estimated that arable land contains up to 53,000 per acre (130,000/ha) of worms, but more recent research has produced figures suggesting that even poor soil may support 250,000 per acre (620,000/ha), whilst rich fertile farmland may have up to 1,750,000 per acre (4,300,000/ha), meaning that the weight of earthworms beneath a farmer's soil could be greater than that of the livestock upon its surface. Richly organic topsoil populations of earthworms are much higher – averaging 500 per square metre (46/sq ft) and up to 400 g2 – such that, for the 7 billion of us, each person alive today has support of 7 million earthworms.

The ability to break down organic materials and excrete concentrated nutrients makes the earthworm a functional contributor in restoration projects. In response to ecosystem disturbances, some sites have utilized earthworms to prepare soil for the return of native flora. Research from the Station d'écologie Tropicale de Lamto asserts that the earthworms positively influence the rate of macroaggregate formation, an important feature for soil structure. The stability of aggregates in response to water was also found to be improved when constructed by earthworms.

Though not fully quantified yet, greenhouse gas emissions of earthworms likely contribute to global warming, especially since top-dwelling earthworms increase the speed of carbon cycles and have been spread by humans into many new geographies.
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