Researchers from Loughborough University in England have discovered that the common sundew (Drosera rotundifolia), a carnivorous plant found in bogs across northern Europe, appears to be going vegetarian in response to human-created pollution.
Of course, the small, sticky, formerly meat-eating plant isn't changing its diet to make a political statement. Rather, increased levels of nitrogen in the soil due to the burning of fossil fuels means the plant no longer needs to catch insect prey to get the essential nutrients it requires to survive.
"If there's plenty of nitrogen available to their roots, they don't need to eat as much," explained Dr. Jonathan Millett, the report's lead author.
Nitrogen pollution is one byproduct of the burning of fossil fuels, and it is deposited into the ecosystem by rainfall. Because nitrogen isotopes vary depending on whether the element comes from natural or industry-related sources, researchers were able to analyze how much nitrogen the plants were absorbing from pollution as compared to insects. According to the study, plants from areas that were heavily polluted got as little as 22 percent of their nitrogen from insects, compared to 57 percent in control populations.
In fact, the plants weren't just eating fewer bugs. Plants in heavily polluted areas were changing their morphology. For instance, they became less sticky, which limits their ability to catch insects, and they even appear to have changed their color from reddish, which attracts insects, to green, which allows them to engage in photosynthesis more efficiently. In other words, the plants weren't just getting more of their nitrogen from their roots, they were also actively limiting their carnivorous behavior.
Researchers posited that the reason for the changes is that the plant has to spend a lot of energy to develop its prey-capturing architecture. Developing its specialized equipment also comes at a cost to its ability to collect energy. So, when meat-eating is no longer necessary, the plants can scale back their carnivorous diet.
In a way, there's a lesson in this for carnivorous humans, too. Meat-eating is notorious for being an inefficient source of nutrients and calories (e.g., it takes about 15 pounds of grain to produce just 1 pound of beef). This is one argument posed by activist vegetarians for why meat-eating should be scaled back when meat is no longer a necessary food source.