While much of the public’s attention—and funding for scientific research—has been funneled into efforts that focus on the impact of plastics in marine environments, the ones in our soils may be just as serious a problem. In response, policymakers and scientists alike are starting to shift their attention to the negative impacts of plastics on land.

According to a recent report by the United Nations’ Food and Agriculture Organization (FAO), the earth’s soils may be more saturated with plastic pollution than oceans and an estimated 80 percent of plastics found in marine environments are first disposed of on land. The report announces the first global call for action to protect agricultural soils from plastic pollution based on the “6R principle” for sustainable plastic use, which involves refusing, redesigning, reducing, reusing, recycling, and recovering plastics.

Agricultural production is a growing source of global plastic use, accounting for 3.5 percent of global plastic production, according to the FAO report. The report estimates that in 2019, the agriculture sector used 12.5 million tons of plastic, with crop and livestock sectors accounting for 10 million tons. While that may seem like an insignificant slice of the overall problem, the threat lies in these products’ proximity to earth’s soils and the food we consume. Commonly used agricultural products, such as non-biodegradable plastic mulching films, greenhouse films, and polymer-coated slow-release fertilizers, have a tendency to break down in the soil, leaving behind pieces of plastic ranging in size from large to microscopic. These pieces have unknown, yet potentially detrimental, implications for ecosystems and human health.

While scientists note significant gaps in knowledge about how plastics affect soils, a growing body of research has shown that they can serve as vectors for chemicals and pathogens harmful to human health. They can also disrupt soil biology and crop establishment, which could negatively impact food security.

“Currently with all the use of plastics in agriculture, the focus is on what benefits they deliver,” said Richard Thompson, a co-author of the report. While plastics offer farmers benefits in the form of increased yields and resource efficiency, “there’s very little focus on their potential for harm,” said Thompson.

The Rise of ‘Plasticulture’

The term plasticulture describes the use of plastic products in nearly every facet of agricultural production, from growing seedlings and preventing weed pressure to storing food. It has been touted as a method for increasing crop productivity and improving food security.

The use of plastic mulching films, for example, has been shown to increase water-use efficiency in crop fields. Polymer-coated, controlled-release fertilizers have also been shown to increase yields and reduce runoff by slowly releasing nutrients. Plastic storage can increase the longevity of harvested crops, and lightweight plastic bins can lead to cheaper, more efficient transport to processors and retailers. Plastic-covered greenhouses extend growing seasons in harsh weather conditions.

“It’s not about stopping the use of plastic in agriculture, because there are benefits,” said Luca Nizzetto, a senior research scientist cited in the FAO report who specializes in microplastics in terrestrial environments with the Norwegian Institute for Water Research. “But they have to be verifiably safe for the environment and used in a sustainable way.”

While land-based experimentation has been limited, some research has shown that plastics can absorb and concentrate pollutants and harbor pathogens—and have detrimental effects on human and environmental health. For example, an experiment led by Mary Beth Kirkham, a plant physiologist and distinguished professor of agronomy at Kansas State University, found that wheat plants grown in soils that contain microplastics absorbed more cadmium than plants grown in soils where the contaminant was present on its own.

The experiment’s findings lead Kirkham to believe that more plastics in our soils may lead to elevated levels of toxins in our food. “These are concerns, but they are big question marks, too,” said Kirkham. “We need more studies.”

Many of the products used in agricultural production have a relatively short lifespan—12 months or less—and few options exist for end-of-life recycling, especially in rural areas with a shortage of waste management infrastructure.

When no collection system exists for these plastics after they’re no longer of use, a farmer has limited and potentially hazardous options for getting rid of them: take them to the landfill, burn them, or keep them in their fields. Burning plastics releases harmful chemicals, like dioxins, which can cause carcinogenic effects when inhaled by humans. Kirkham says she has gotten calls about farmers tilling plastic mulching films into their fields, citing a lack of access to machinery for retrieval. When agricultural plastics are left in fields, they break down into smaller particles that have the potential to persist in the soil for a very long time. Earthworms can ingest and transport these particles to deeper levels of the soil, and their accumulation can lead to impediments in the flow of moisture and nutrients and may inhibit the soil’s ability to retain water.

While plasticulture is given credit for boosts in production in the short-term, little evidence has been gathered about the long-term impacts of agricultural plastics on soil health and, thus, the long-game of food security.

“Yes, we need more science to fully understand, but it’s clear that there’s an urgency to act,” said Giulia Carlini, a senior attorney with the Center for International Environmental Law, an organization that advocates for the creation of an international agreement on curbing plastic pollution. “We should apply the precautionary principle because we’ve learned so many late lessons from early warnings.”

Expanding Producer Responsibility

Those concerned with agricultural plastics in the soil are looking to address the problem from several fronts.

Acknowledging that there is no silver bullet, the FAO report outlines a variety of recommendations that span several different policy arenas, including eliminating the use of the most problematic agricultural plastics, investing in biodegradable substitutes, and mandatory extended producer responsibility obligations for appropriate end-of-life management. The authors of the report also suggest establishing an international, voluntary code of conduct on sustainable use, which will be discussed by the FAO’s Committee on Agriculture in July, said Thompson, one of the report’s authors.

“A voluntary code can have a much wider scope, because it doesn’t require consensus between all the countries that are debating it,” said Thompson. “It can set responsibilities for a wider range of stakeholders rather than just national governments.”

The report also supports mandated solutions. Carlini and her colleagues, for example, are gearing up for negotiations on drafted resolutions for a global, legally binding plastics treaty at the U.N. Environment Assembly (UNEA) in Nairobi this month. While countries joined together at UNEA in 2019 and previous sessions to pass a resolution on marine plastic pollution, Carlini is advocating for policymakers to take a broader approach.

“We’re extracting fossil fuels and using them to make chemicals and pesticides and plastics that are then polluting the world,” said Carlini. “There are links between the climate crisis, plastics, biodiversity, and toxics. They are all part of the same story.”

Meanwhile, Nizzetto is working with PAPILLIONS, a research project supported by the European Commission to study the lifecycle of agricultural plastics and their long-term impacts. The group is calling on policymakers to establish sustainability criteria for agricultural plastics, including biodegradability standards, life-cycle traceability, and increased funding for research that investigates the complex interactions among plastics and other pollutants in soils, including pesticides and heavy metals.

In the U.S., potential solutions to address agricultural plastics have been slower to develop.

The FAO report emphasizes solutions that embrace the “polluter pays” principle, including Extended Producer Responsibility (EPR) schemes that promote closed-loop recycling of agricultural plastics, funded by the corporations that produce them. With a mandated EPR system, the producers of agricultural plastics would be responsible for funding and developing the infrastructure needed to collect and recycle those materials based on government regulations that outline sustainable management.

“If the corporation is required to pay for end-of-life disposal and it’s costly, they will be incentivized to reduce the toxins in their products or design them for recyclability,” said Suna Bayrakal, director of policy and programs at the Boston-based Product Stewardship Institute. “EPR laws shift the financial and management responsibility to the producers, all while retaining government oversight.”

EPR programs currently exist in 33 states and Washington, D.C. for a variety of products like batteries, paint, pharmaceuticals, and tires. Last year, Maine and Oregon passed the first-ever U.S. EPR laws to require companies that put consumer packaging on the market to contribute to the costs of collection and recycling. But few of these mandates cover agricultural plastics, aside from California’s recycling program for pesticide containers of 55 gallons or less.

Voluntary programs do exist, such as the Ag Container Recycling Council, which collects agricultural plastics around the U.S., but these programs leave room for “free riders” that benefit from the collection infrastructure but don’t contribute toward the cost of a product’s end-life management.

“If we’re not going to have mandatory EPR, we at least need voluntary EPR, with the addition of social capital,” said Anne Macmillan, an agrichemical toxicologist who has worked on the recyclability of agricultural plastics with the Vermont Agency of Agriculture, Food, and Markets for over 20 years. Without industry funding dictated by mandatory programs, or encouraged by voluntary EPR, she says, either local governments or farmers are going to have to shoulder the costs. “[Industry] has the deep pockets,” she said. “Farmers don’t.”

Plus, farmers don’t always have options for where to send their waste. “The markets come and go based on the price of oil, so there’s no stable place for farmers to turn to recycle their materials,” said Macmillan. Even so, farmer-backed efforts to spur EPR development have little momentum in the U.S.

Bayrakal says national barriers to implementation of EPR can be traced to a general lack of knowledge about EPR models, as well as to a range in the levels of industry engagement and support for EPR. “Most of the [EPR] laws are state level, but producers can be global,” said Bayrakal. “Some of these corporations and their trade associations, for example, have counterparts in Canada that are implementing laws there that they’re resisting in the U.S.”

Even if EPR schemes were more widely utilized, they wouldn’t necessarily address the environmental problems that arise from extracting and transporting fossil fuels to feed global plastic demand, which is why the FAO report emphasizes the need for coordinated action to reduce the use of plastic altogether.

“If we’re looking at solutions to the plastic crisis, which would include the plastics we find in agriculture,” said Carlini. “We should go for a global solution, because it’s a global problem.”