It’s Not Just an Ocean Problem. Microplastics Pollute Rivers, Lakes, and Land, Too
Eighty percent of microplastics originate on land, but their impact on freshwater and terrestrial environments remains unclear.
A University of Toronto ecologist has issued a clarion call for more research into microplastic pollution in rivers, lakes, and on land, saying scientists need to learn more about the health of those locations if they want to clean up the Great Pacific Garbage Patch and other areas polluted with plastic trash.
Writing in the journal Science, Chelsea Rochman argued that scientists have a clear picture of the toll that small, plastic particles less than 5-millimeters (about a fifth of an inch) long have taken on the ocean. But 80 percent of microplastics in the ocean originate on land. It’s essential to investigate their effects when they first enter the environment, she said.
“As we’ve learned more and started to think about mitigation, we’re forced to think about where it’s coming from and where it’s going so that we can cut it off at the source,” Rochman told Seeker.
Recently, for example, researchers wrote in the journal Scientific Reports that the Great Pacific Garbage Patch between California and Hawaii covered 1.6 million square kilometers (almost 620,000 square miles), as much as 16 times larger than previous estimates. Microplastics comprise around 8 percent of the total mass of the patch but 94 percent of the 1.8 trillion pieces of trash floating in it. Fishing nets comprised around half of the patch.
Fish, birds, and other creatures eat the microplastics, which can harm them internally. Humans consume the plastic when they eat the fish, too. Plastics have also been shown to kill coral reefs and wreak other damage to marine ecosystems.
Microplastics were first reported in freshwater lakes five years ago, Rochman wrote. Today, they’ve been found in water bodies nearly everywhere on the planet. That’s a problem, she argued, because freshwater and land-based ecosystems contain five times more biodiversity than the oceans.
It’s not clear, however, if microplastics are causing more or less damage in lakes, rivers, and the soil. Saltwater fish drink water. Freshwater fish absorb water through their skin and gills. One might assume the former would be more likely, therefore, to suck up microplastics. But rivers are a major conduit for that trash, so freshwater fish could be ingesting more plastic than their seagoing counterparts. Scientists needed to look into the questions more closely, Rochman said.
The problem is expected to grow worse.
Humans dump around 31.9 million metric tons (35 million tons) of plastic per year into the environment, including plastic and lint that water treatment plants discharge into waterways or put into in sewage sludge that farmers then spread on their fields as fertilizer. As much as 12.7 million metric tons (around 14 tons) of those microplastics reach the ocean every year.
That pollution is expected to grow exponentially in the coming years, meaning problems that fish and people face today are likely to become worse in the next few decades.
Rochman hopes that people could alter their perception of microplastics, thinking of them less like litter on beaches but more like toxins that are dangerous wherever they go, like PCBs and other chemicals.
“Can we at least just flip our thinking about plastics as this ocean pollutant to thinking about it like we think about these other persistent global pollutants?” she asked. “If we think about it that way, then we absolutely need to think about it in terrestrial and river systems.”