Research also shows that microplastics can stunt the growth of earthworms and cause them to lose weight. The reasons for this weight loss aren"t fully understood, but one theory is that microplastics may obstructs earthworms" digestive tracts, limiting their ability to absorb nutrients and so limiting their growth. This has a negative impact on the wider environment, too, the researchers say, as earthworms play a vital role in maintaining soil health. Their burrowing activity aerates the soil, prevents erosion, improves water drainage and recycles nutrients.