Plummeting earthworm population poses threat to environment

• Earthworms are declining by up to 2.1% per year
• Plants and animals rely on earthworms for nutrition and food
• Decline in numbers “hugely concerning”, experts say 
• Earthworms help create nearly 140 million tonnes of food per year

Earthworms are a keystone species and you can tell how healthy an ecosystem is by how many there are

The UK’s food chain, environment and livestock could be harmed if the earthworm population, which has declined by a third in the past 25 years, continues to fall.

According to a report from medical journal PLOS One, the decline, which is happening at a rate of 2.1% a year, will likely have a knock on effect on the soil quality and crop yields.

This would be disastrous for thrushes, wading birds and small mammals which eat them and harm the UK’s natural environment.

The report, titled ‘Collation of a century of soil invertebrate abundance data suggests long-term declines in earthworms but not tipulids,’ said that earthworms are vital for the environment and contribute an average of 140 millions tonnes of food into the food chain per year. 

Scientists have even said that earthworms would be the world’s fourth-largest food producer if they were a country, and without them, the world’s food supply will drop to dangerously low levels. 

This is because earthworms are a keystone species, which is an organism that helps measure the health of an ecosystem.

Earthworms are a staple diet for woodlands birds, and their decline has meant there are 37% fewer woodland birds in the UK than there was in 1970. 

It also affects the health of plants, which can grow up to 30% bigger with vermicompost –  a type of compost created from worm casts.

Researchers also said the decline in earthworms is down to the increasing UK’s human population. 

It has also been escalated by the use of chemicals, such as pesticides and fertilisers, which are toxic to earthworms.

Loss of habitat through urbanisation and heavy rain, which forces earthworms up to the surface, have also contributed. 

Additionally, heavy machinery compresses the soil, making it difficult for earthworms to burrow. These narrow tunnels help to aerate topsoil, the layer of earth on which 95% of human food is grown. 

James Pierce-Higgins, a zoologist at Cambridge University, was quoted in The Times describing the fall in earthworms as “hugely concerning”. 

“They [earthworms] are responsible for nutrient cycling, for aerating the soils,” Pierce-Higgins explained. 

“And they’re important food. We see declines in some of our thrushes and waders that feed on earthworms.

“It does seem to be the case on farmland and also, slightly to our surprise, in woodland.”

Dr Ailidh Barnes, research ecologist from the British Trust for Ornithology (BTO), and co-author of the paper, explained that any decline in the earthworm population could be a “contributing factor” to an overall decline in the ecosystem. 

“If robust, our results identify a previously undetected biodiversity decline that would be a significant conservation and economic issue in the UK”, Barnes said.