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Why do earthworms surface after rain?

Farmer Ramesh Hanumaiya displays soil with earthworms in it in Anantapur district in the southern Indian state of Andhra Pradesh, India, Wednesday, Sept. 14, 2022. This soil used to be as hard as a brick, Ramesh said. Its now like a sponge. The soil is rich with the nutrients and life that's needed for my crops to grow on time and in a healthy way. (AP Photo/Rafiq Maqbool) (Rafiq Maqbool, Copyright 2022 The Associated Press. All rights reserved)

JACKSONVILLE, FL – After heavy rainstorms, your surroundings may feel different and perhaps you notice a peculiar smell or a sudden drop in temperature.

But it’s not just the weather that changes, you might also spot earthworms wriggling around on the surface.

These small creatures are highly sensitive to their environment, and the rapid changes from heavy rain make their escape to the surface easily observable.

So, why do these essential soil dwellers come above ground after a downpour?

According to researchers, earthworms surface to escape drowning.

Earthworms absorb and lose moisture through their skin. Earthworms can live under submerged conditions if the oxygen content of the water is high enough. But when soil becomes waterlogged, the oxygen levels drop, making it difficult for these creatures to breathe. To avoid suffocation, they move to the surface where oxygen is more accessible.

Recent studies offer even more insights into this behavior.

Research published in Soil Biology and Biochemistry in 2023 found that heavy rains can alter soil pH and temperature rapidly.

These changes can stress earthworms, pushing them to the surface for more stable conditions. Additionally, a 2024 study in Ecology and Evolution discovered that waterlogged soil redistributes nutrients and affects microbial activity, further motivating earthworms to escape to the surface.

In essence, the appearance of earthworms after a rainstorm is more than just a quirky observation, it’s a survival strategy.

As they react to oxygen depletion, pH changes, and shifting nutrient dynamics, these soil engineers are doing what they can to weather the storm.


About the Author

After covering the weather from every corner of Florida and doing marine research in the Gulf, Mark Collins settled in Jacksonville to forecast weather for The First Coast.

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