A review of evidence led by experts at the Centre for Ecology & Hydrology (CEH) has highlighted the need for further research to determine the extent to which microplastics are polluting and harming land-based ecosystems.
The review, published in the journal Science of the Total Environment, has revealed a large degree of uncertainty as to how much, and in what way, waste plastic may be damaging terrestrial environments, and what size and type of plastic might be the biggest problem.
Researchers also accept that it is not fully understood to what extent microplastic pollutants are released into the environment through everyday products, accidentally or through wind transfer.
Two samples showing microplastic particles collected from a tributary of the river Thames
In 2014, in Europe, more than 311 million tonnes of plastic was produced and it is estimated that by 2050 this will spiral to 33 billion tonnes a year. Each year it is believed between 473,000 and 910,000 metric tonnes of plastic waste is released and retained within land-based environments – or between 4 and 23 times the amount estimated to be deposited in oceans.
Lead author Alice Horton, a research associate in microplastics and toxic pollutants at the Centre for Ecology & Hydrology, said there are still questions that need to be answered to fully understand the potential for 'microplastics to have detrimental effects on the physiology of species across many ecological niches'.
Alice said, "There is evidence to show that microplastics can have harmful effects on organisms, hindering their ability to feed, reproduce and defend themselves against predators, with effects likely to vary between types and sizes of microplastics.
Graphical abstract from Horton et al (10.1016/j.scitotenv.2017.01.190): conceptual diagram of microplastic sources and flows throughout and between anthropogenic, terrestrial, freshwater and marine environmental compartments.
"This could have significant knock-on effects within ecosystems. Despite growing interest in microplastics within the wider environment, the majority of studies to date have been carried out within the oceans on marine organisms. Here at CEH we are interested in the start of the chain, when microplastics first enter the environment to land and rivers and the organisms that may be affected there."
"At CEH we are interested in the start of the chain, when microplastics first enter the environment to land and rivers and the organisms that may be affected there." Alice Horton, Centre for Ecology & Hydrology
The review, which was funded by the Natural Environment Research Council, has led to collaboration to address possible effects of plastics in terrestrial environments with researchers at the University of Exeter, UK, and the University of Leiden in the Netherlands. It highlights key areas for future research including:
- Determining the current extent of microplastic pollution in terrestrial environments, and how this compares to known contamination in aquatic environments. Also, which polymers and sizes are most abundant and if this varies across habitats and regions.
- Understanding the extent to which environmental conditions and properties of different plastic materials affect microplastic behaviour and bioavailability under the conditions that are found in freshwater and terrestrial environments.
Dr Claus Svendsen, co-author of the review and a principal scientific officer at the Centre for Ecology & Hydrology, said, "The review shows that the types and concentrations of plastics found in the terrestrial environment varies greatly depending on local sources.
"When combined with laboratory experiments this shows that very high levels of some plastics cause little effect, while other plastics do cause effects. This demonstrates how far we have to go to understand this problem.
"...very high levels of some plastics cause little effect, while other plastics do cause effects. This demonstrates how far we have to go to understand this problem." Dr Claus Svendsen, Centre for Ecology & Hydrology
"The one clear thing is that once in the environment plastics will remain for a long time and will not be easy to remove or manage."
Full paper reference: Alice A Horton et al. Microplastics in freshwater and terrestrial environments: Evaluating the current understanding to identify the knowledge gaps and future research priorities. Science of The Total Environment, doi: 10.1016/j.scitotenv.2017.01.190, published online 4 February 2017.
In September 2016 CEH scientists published a study which showed the first evidence of microplastic particles in UK freshwater environments. The CEH study found high numbers of microplastic particles in all studied sites within tributaries of the river Thames, including areas with a very low surrounding population expected to have very little pollution. This research highlighted the complexity of determining the extent of environmental microplastic pollution with more studies needed to also determine the sources, fate and effects of these within the Thames Basin and surrounding environment.
Read Alice Horton’s blog post giving more details of the research: First evidence of microplastics in UK freshwater environments