Normally, we applaud efforts to reduce meat consumption. But in this case, it’s a little disturbing.
Scientists at Loughborough University discovered that acid rain is causing carnivorous plants to change their behavior and become vegetarian. Normally, these plants depend on living things that fall into their traps to provide nutrients necessary for survival. According to the study’s lead author Dr. Jonathan Millet, nitrogen pollution is supplying carnivorous plants on Swedish bogs with so many nutrients, they don’t need to eat as many flies.
To arrive at this conclusion, Millet examined drosera rotundifolia, otherwise known as the common sundew, which grows in rain-fed bogs across much of northern Europe. These habitats are nutrient-poor, so the plant needs to boost its nitrogen intake by trapping midges and other insects with its sticky leaves.
Unfortunately, humans’ increased use of fossil fuels means that there’s more nitrogen in the air, and eventually this acidic rain falls on the bogs. Millet’s study shows that this artificial rain of fertilizer is now making carnivorous plants lose interest in insect prey. He found that plants in lightly-polluted areas got 57 percent of their nitrogen from insects; in areas that receive more nitrogen deposition, that figure fell as low as 22 percent.
It’s taken millions of years for the common sundew to develop the ability to trap and consume living prey, so it’s shocking to see such a rapid change in behavior. Millet says previous research shows that the plants can control the stickiness of their leaves, as well as the color which helps them attract the insects in the first place. It may be that with so much nitrogen available in the ground, the plants are retracting the tools that helped them catch bugs in an effort to save energy.
Although it might seem like minor change in an insignificant plant species, such a change can have a big impact on the surrounding ecosystem.
“In the sites with more nitrogen deposition, these plants now get much more of their nitrogen from their roots, but they still have to bear the residual costs of being carnivorous, and other plants without these will be better able to survive,” said Millett. “So it’s quite likely we’ll see less abundance and perhaps local extinctions from carnivorous species. The individual plants get bigger and fitter, but the species as a whole is less well adapted to high-nitrogen environments and will lose out over time.”
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