While evidence around the globe shows plastic pollution is getting out of hand, scientists in Cambridge are betting on plastic eating caterpillars to reverse the catastrophic trend. Each year, about 80 million tonnes of the plastic polyethylene are produced around the world. The plastic is used to make shopping bags and food packaging, among other things, but it can take hundreds of years to decompose completely. Instead, microplastics make their way up the food chain, as a range of animals throughout the marine environment, including corals and zooplankton, consume these particles.
Even if they don’t kill the animals, these toxic chemicals may affect the animals’ behavior and hormone levels, and their concentration can only rise when producer organisms such as plankton are consumed by larger ones and end up at the bellies of apex predator species, like killer whales. Sometimes pollutants don’t cause obvious health issues but may alter the way an animal feeds, moves or socializes. Exposure to some chemicals, for example, causes feminization in males, resulting in reduced breeding activity and ultimately affecting a population’s stability.
Last month, one of the highest concentrations of toxic pollutants ever recorded in a marine mammal has been revealed in a Scottish killer whale that died in 2016. The examination of the whale found she was at least 20 years old, well above the age of sexual maturity, which ranges from six to 10 years old. However, analysis of the ovaries shows she never bore a calf, probably because pollutants in her blubber had caused infertility. The entire pod may have been left barren, as no calf has ever been seen in the 23 years the group has been monitored, so it now safe to assume that the region’s whales are moving towards extinction.
Another interesting pollution record has been recently revealed; Henderson Island, a tiny landmass in the eastern South Pacific, has been found by marine scientists to have the highest density of anthropogenic debris recorded anywhere in the world, with 99.8% of the pollution plastic. The nearly 18 tonnes of plastic piling up on an island that is otherwise mostly untouched by humans have been pointed to as evidence of the grotesque extent of marine plastic pollution. The largest of the four islands of the Pitcairn Island group, Henderson Island is a Unesco World Heritage Listed site and one of the few atolls in the world whose ecology has been practically untouched by humans. Or so we thought, up until scientists published images of hundreds of crabs living in rubbish such as bottle caps, cosmetics jars, and Barbies’ heads. Only last February, scientists reported “extraordinary” levels of toxic pollution in the Mariana trench, with plastic waste facilitating the spread of industrial chemicals to yet another of the most remote and inaccessible places on the planet.
It seems that “extraordinary discoveries” are synonymous to “really disturbing news”. It is also obvious that marine pollution is not up for debate. On the contrary, the situation calls for urgent action. And this is where plastic eating caterpillars come in. Researchers at Cambridge University have discovered that the larvae of the moth, which eats wax in bee hives, can also degrade plastic. Experiments show the insect can break down the chemical bonds of plastic in a similar way to digesting beeswax. They think microbes in the caterpillar – as well as the insect itself – might play a role in breaking down plastic. If the chemical process can be identified, it could lead to a solution to managing plastic waste in the environment.
Eventually, can we really rely on bugs to do our dirty work for us?
How thoughtful of nature to provide bugs that eat our rubbish. Is this the end of the landfill, turtles with plastic-congested stomachs, and trees adorned with tattered ribbons of shopping bags? These creatures, the larvae of the greater wax moth (Galleria mellonella), can devour polyethylene, which along with the closely related polypropylene is the main type of plastic found in waste. But you’d need an awful lot of them to make a significant dent in the plastic waste problem. The UK alone discards almost 2m tonnes of this stuff every year. At the rate of consumption reported by the researchers – one worm gets through about two milligrams of plastic a day – you’d need billions of caterpillars eating constantly all year round to deal with that.
On the researchers’ behalf, you might say Cambridge has no interest in unleashing a swarm of bugs with a curious appetite for rubbish into our waters, thus endangering other species’ populations. They are interested in the natural process occurring when the worms consume and eventually dissolve the chemical bonds of plastic. Alternatively, it might be possible to extract the particular enzymes the caterpillars use and put them to work on their own – a kind of concentrate of gastric juices. But what of the bug’s excretions? Is it really able to digest and degrade plastic, or will the omnipotent and omnipresent debris survive in the moth’s poop and return to haunt us in the form of the stool? Eventually, can we really rely on bugs to do our dirty work for us?