Acid Rain Makes Meat-Eating Plants Go Vegetarian

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.”