This is the Mystic River. It runs right through Medford/ Somerville and empties into the Boston Harbor. And it could very well be located in your backyard. It’s home to many local species. It provides a place for leisure. You can relax, you can ride your bike, run, read, boat, canoe, kayak, make new friends and hang out with old ones. It’s a place where memories are made.

But, behind all the beauty the Mystic River provides, there is a threatening force at work. Water chestnuts, or Trapa natans as scientists call them, is a Eurasian plant that thrives best in warmer temperate environments. They were first cultivated in nearby Cambridge, Massachusetts in 1877. And by 1879 they were found in the Charles River.

The water chestnut stem is generally about one meter long. It’s fruit a small black nut like structure with four sharp horns. The fruit grows underwater and the water chestnut’s leaves allow it to float on the surface. But, wait a second. How could something this small and plant-like be causing such a big problem for the Mystic River? We went to find out more.

This is Beth. She works for the Mystic River Watershed Association. An organization whose goal is to protect this river from invasive species like the water chestnut. This is Patrick. He specializes in plant ecology and he told us a lot about what makes the water chestnut so bad.

We could have a diverse set of plants if it were not for this plant that seemed to take over. The plant may contribute to a decrease in dissolved oxygen values in the water. The plants actually spread at a density that could decrease the ability for people to recreate and then I think also nobody really wants to see a river just covered with green. They really want to see some open water as well.

Okay, great. But, we still didn’t understand what made this small plant so bad. What is an invasive species anyway?

Well, invasive species is a species that basically is spreading through the landscape without much control. Usually, we think of them as non-native plants.

So, it turns out that this small plant multiplies and multiplies and takes away oxygen and room from other plants and animals in the Mystic, making it harder for them to survive. And, not only that, but their presence makes for one ugly river. When they grow in the summer, the water chestnuts literally cover the surface of the water. Who wants to kayak on that?

Not us. But, invasive species, aren’t just in the Mystic. They are all over the place, threatening to destroy the biodiversity of all of our rivers and lakes, and forests. For instance, zebra mussels, native to southern Russia, are plaguing the Hudson River in New York and are taking away oxygen from native fish and plants.

Purple Loosestrife is popping up all over the country, including states like Minnesota, Utah, and Maine. And there is a bright yellow shrub called French Broom all over California and the Northwest. Gross. Wow, they’re everywhere. And we’ve only mentioned a few. There’s no way you can do anything about it? Wrong. There’s so much you can do to help save your local environment.

Folks are interested in getting involved and we’re always looking for more volunteers. These plants, the seeds can last for a really long time so its a multi-year effort we have underway to remove the water chestnuts. And we’ve actually been partnering a lot more with cooperations and community groups that can recruit a whole new base of volunteers.

So I think the biggest thing that people can do is get involved in an issue, to join an organization like the Mystic River Watershed, join an environmental club and choose an issue to work on as a group and leverage everybody’s collective efforts towards finding solutions.

You can attend a community event and check our website for deals at mysticriver.org. You should like us on Facebook and Twitter and all of that.

The evil water chestnut can be conquered. But it starts with you. First you have to recognize the problem. You’ve done that by watching this video. Second, go do research. Go to the library or go online to learn what you can. Third, take action. Join projects in your community that work to fight and prevent invasive species.