Earthworms at Risk

Any gardener or school child can tell you that earthworms are good. Earthworms eat dead, rotting vegetation and excrete nutrient-rich castings that help plants grow. Their tunnels bring oxygen down through the soil and drain excess rainfall so plant roots can survive. Earthworms help produce the food we eat, whether that food is grown in your backyard or in vast fields in Iowa. So when scientists tell us that earthworms in soil contaminated with plastic are in danger, we should be concerned.

A recent study shows that eating plastic is harmful to earthworm health. Scientists reporting in Environmental Science and Technology found that worms (Aporrectodea rosea) lost 3% of their body weight after 30 days in soil contaminated with HDPE compared to a control group of worms that gained 5% body weight in soil with no plastic over the same time period. HDPE is a common type of plastic used for plastic bags and bottles, like milk jugs.

We don’t find many plastic bags and milk jugs in agricultural fields. However, plastic is used in agriculture more than ever before. Plastic covers greenhouses, wraps bales of silage, prevents weeds, lines irrigation ponds. It’s used for plastic netting to keep birds from eating crops, pots to grow seedlings in and drip irrigation. Agricultural plastic is very useful. Theoretically it can be recycled, yet once the useful life of agricultural plastic is over, it’s more likely to be landfilled, burned, or left in a pile on site that will eventually fragment into small pieces and contaminate soil. Microplastics from toothpaste, soaps and washing synthetic clothes are also unintentionally added to soil when sludge from sewage treatment plants is spread over fields as fertilizer.

We first recognized that plastic waste was a problem in marine environments, and most studies focused on the effects of plastic on marine animals. Plastic flows downstream into oceans where it breaks apart into small pieces and is eaten. Oysters that eat plastic have slow sperm, shriveled eggs and below-average offspring. Lugworms, marine cousins of the earthworm, are less fleshy, less numerous and less successful at reproducing in plastic-infiltrated mud. It’s not only filter feeders and mud eaters that eat plastic. Anchovies can’t differentiate between plastic and food when plastic is colonized by algae, and algae quickly colonizes plastic in the ocean. The effects of plastic on terrestrial animals haven’t been studied much until now. 

Recent scientific studies show that problems with plastic waste are not confined to oceans. Tiny fragments of plastic are everywhere. Plastic floats on the ocean surface, settles on deep ocean sediments and is suspended in the water between. Plastic is in remote mountain air, arctic snow and agricultural fields. It’s in our drinking water and our excrement.

Though it’s an enormous problem, there are things we can do to help. Be aware of the plastic you use. Are there alternatives? Can it be reduced or reused? Help clean up plastic waste in the environment too. BlueTubes make this easy. Grab a bag from a BlueTube next time you’re at the beach, pick up trash and throw it away. Reuse your plastic bags by adding them to a BlueTube and they will be used by others to keep the beach clean and keep plastic out of the ocean. No BlueTube at your beach? Buy one here!