Climate change: hungry caterpillars and their feces increase carbon emissions

Carbon emissions remain a widespread and growing problem around the world, but not only humans and factories create them, but also the humble and hungry caterpillar, a new study revealed.

Caterpillars may not seem like the likely source of the most emissions, but looks can be deceiving.

The caterpillars in question are invasive gypsy moths Lymantria dispar dispar and moths from the forest tent caterpillar Malacasoma dystria. Outbreaks of these species occur every five years in temperate forests. During these outbreaks, the caterpillars consume so many leaves and defecate so much that the very cycle of nutrients between the land and nearby lakes is disrupted on a large scale.

This is particularly evident with carbon and nitrogen. Caterpillar droppings, called droppings, are rich in nitrogen. It often ends up washing lakes and fertilizing microbes. This, in turn, helps them metabolize, which releases more carbon dioxide into the atmosphere. This makes it difficult for lake algae that reduce carbon dioxide through the carbon cycle to keep up.

forest tent caterpillar moths. (credit: Wikimedia Commons)

“These insects are basically little machines that turn carbon-rich leaves into nitrogen-rich droppings.” explained Professor Andrew Tanentzap, Director of the Ecosystems and Global Change Group in the Department of Plant Sciences at the University of Cambridge and lead author of the paper, which was published in the academic journal Communications from nature.

“The poop falls into the lakes instead of the leaves, and this significantly changes the chemistry of the water; we think it will increase the extent to which the lakes are sources of greenhouse gases.”

The study is believed to be the most extensive study on insect outbreaks affecting freshwater carbon and nitrogen dynamics, combining 32 years of government data on insect outbreaks and lake water chemistry in 12 basins. different lakes in Ontario, and even made use of satellite remote sensing in forests and leaves.

As time goes on, this is only expected to get worse. The caterpillars are expected to expand their range northward as the climate continues to change. This means that the damage they are causing in the south could soon begin to occur in the north. As the North has even more freshwater lakers, their range could be further expanded.

They will also be favored by climate change, as broadleaf deciduous trees are likely to be favored by rising temperatures, and this will only help the caterpillars wander further away.

“Leaf-eating insect outbreaks can reduce dissolved carbon in lake water by nearly a third when the trees around the lake are primarily deciduous. It’s amazing that these insects can have such a pronounced effect on water quality, ”said Sam Woodman, graduate student and first author of the Global Change and Ecosystems Group study.

He added that “from a water quality perspective they are a good thing, but from a climate perspective they are quite bad, yet they have been completely overlooked in climate models.”

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