Soil ecosystem effects of microplastics

Microplastics are now ubiquitously present in the environment – a news item on the BBC in August 2019 even described their presence in snow falling in the Arctic (“Why is there microplastic in Arctic snow?“)  Generally however when thinking about the detrimental environmental and ecological effects of microplastics our thoughts tend to focus on the world’s water bodies, and in particular its (our) oceans. Research published in the “early view” (or “ASAP”) issue of the journal Environmental Science and Technology ought to cause us to also think about the effects of microplastics on terrestrial ecosystems, including the terrestrial ecosystem that we rely upon for much of our food – soils!

Soils are a major – often largely ignored – sink for microplastics, much of it from the degradation of larger plastic objects. Researchers in the Applied Ecology Research Group of Anglia Ruskin University (ARU) in the UK have investigated the biophysical effects of different kinds of microplastics on soil structure and fauna, and on the productivity of perennial ryegrass under experimental conditions. Ryegrass is a group of grasses that are often grown for forage for animals, for preventing soil erosion and in ornamental lawns etc. The researchers at ARU found, for example, that the presence of conventional high density polyethylene (polyethylene is the most widely used substance in the manufacturing of plastic) in soil reduced the biomass of earthworms, led to a reduction in soil pH (increased acidity) and changed soil structure. The latter has implications for soil stability, or the ease at which a soil can be eroded.

Other forms of microplastic that are commonly released to the environment, including that made from polylactic acid, was associated with reduced plant (ryegrass) productivity. Polylactic acid is the basis for some “bioplastics”, which are degradable under certain conditions. Note that there is a difference between biodegradable and degradable – this difference with regard to polylactic acid-based plastics is highlighted here.

NUS students should be able to access the above article through the eJournals part of the NUS libraries website.