Plastics are accumulating in the world’s soils at an alarming rate, with detrimental impacts on soil health, biodiversity, productivity, and food security. While improvements with respect to the production and management of agricultural products containing plastics are being made, a UN Environment Programme (UNEP) report is calling for adopting a more holistic approach to food production, including nature-based solutions.

The brief titled, ‘Plastics in Agriculture – An Environmental Challenge,’ explores plastic use in agriculture and the waste problem this entails. It explains that plastics are used extensively in farming, in plastic coated seeds, as well as in mulch film or protective wraps used to modify soil temperature and prevent weed growth over crops. Plastics are also added to biosolid fertilizer, which is spread on fields and used in irrigation tubes, sacks, and bottles. While these products have helped increase crop yields, degraded plastics are contaminating the soil and impacting biodiversity and soil health. Over time, plastic can break down into shards less than five millimeters long and seep into the soil and food chain, impacting human health.

Microplastics in the soil can change the Earth’s physical structure, limit its capacity to hold water, and affect plants by reducing root growth and nutrient uptake. The biggest source of microplastic pollution in soil is fertilizers produced from organic matter such as manure. Although cheaper and better for the environment than manufactured fertilizers, manure is mixed with the same plastic microspheres often used in soaps, shampoos, and makeup.

The brief proposes nature-based solutions such as cover crops as they can shield the soil, suppress weeds, counter soil diseases, and improve soil fertility. However, since they are not meant to be harvested, they can also reduce yields and increase costs. In addition, plastic is inexpensive and easy to work with, making the use of alternatives “a hard sell.” Thus, the report recommends that governments disincentivize the use of agricultural plastics, as the EU has done to restrict certain types of polymers from use in fertilizer. 

While limited research on assessing nature-positive approaches has been undertaken, farming practices, such as natural mulch cover crops, are being considered. Cover crops, such as cereal rye, can be planted during winter and removed prior to sowing or planting. Living cover crops of legumes can provide nitrogen to the main crop. However, barriers, such as lack of context-specific information, education, and training, have prevented the widespread use of cover crops. Increasing uptake requires policy instruments, capacity building, involving a range of stakeholders, financial incentives that compensate for reduced yield, and disincentivizing unsustainable products or practices. 

The brief calls for:

• adopting the precautionary principle, given the limited research on the impacts of plastics in soil;
• developing solutions for stopping the flow of microplastics into the environment;
• preventing microplastics from entering wastewater treatment plants and developing and implementing cost-effective mechanisms for removing the microplastics from sewage sludge;
• accelerating the manufacture of affordable zero-residue biodegradable plastics; and
• better understanding and quantifying the environmental benefits of nature-based solutions. 

The August 2022 brief was featured in a UNEP story on 17 October. [Publication: UNEP Foresight Brief: Plastics in Agriculture – An Environmental Challenge] [Publication Landing Page] [UN Press Release] [UNEP Press Release]