GLENCOE, IL — To protect native plant and animal life sometimes requires sustained human intervention. Once brought into the U.S. for its hardiness, the introduction of European buckthorn is out-competing native life across the country.

At the edge of a lagoon in the dead of winter, a group of about two dozen volunteers is braving the icy conditions to save the local ecosystem.

“We're clearing out invasive species with the goal of making room for native species, which are better for the environment overall, but particularly for the amphibians,” said Maggie Cooper, the coordinator of conservation action at Chicago’s John G. Shedd Aquarium.

Cooper is leading the expedition of volunteers focused in part on the resilient and difficult to destroy invasive European buckthorn.

It was introduced into the U.S. as a means for fence farming and for medicinal purposes more than 200 hundred years ago. It’s an aggressive plant that can soak up precious resources and outcompete native plants.

“If you see a stand of buckthorn and you look at the forest floor, you're not going to see anything else growing up. You're only going to see buckthorn growing in that area,” said Cooper.

The plant also emits a toxin called ‘Emodin’ that can kill or suppress the growth of native vegetation.

“Emodin seeps into the soil and we know how amphibians breathe, sometimes they draw in nutrients and their skin,” said Cooper. “And it's known that amphibians will bring that toxin into their body as well. And that can affect their life cycle, especially in the early stages.”

Conservationists have been battling the invader for decades.

It’s now spread across much of the Northeastern, Midwestern, and Western U.S. with some of the most affected states including Minnesota, Wisconsin and New York.

Equipped with loppers and hand saws, the team will clear out as much of the intrusive shrubs and trees as possible.

Stubs are treated with an insecticide to prevent regrowth. Everything is immediately burned.

“If we couldn't have fires, this wouldn't be half as much fun. Not that I'm a pyromaniac or anything, but you know it warms you up,” said Dan Goodwin.

Goodwin has been volunteering with the conservation action group for more than five years.

“From here to the clearing over there [that] edge is two years’ worth of Saturdays and Wednesdays, so you can have an impact,” he said.

Cooper says despite the gains, the work must be constantly ongoing.

“If we just stopped what we were doing, buckthorn is going to come back in,” she said. “So, we need to continue this fight. We need to be out here year after year, month after month.”

It’s an investment of time and labor to protect native wildlife for years to come.

LONGMONT, Co. — On her 44 acre property tucked in the foothills of the Rocky Mountains, Carol Walker feeds her horses an afternoon treat.

Though Micah and Hermoso are living a sweet life, it still pains carol that they’re kept inside a fence.

"I love them both dearly, but I wish that they had stayed wild and free," she said.

A 1971 law protects wild horse numbers. However, the two adopted mustang brothers are in her care because they were captured in separate roundups by the Bureau of Land Management, the government agency tasked with keeping track of their numbers.

If there are too many, the bureau, or the BLM as it's referred to, herds them into corrals via helicopter, puts them into a long-term holding facility, examines them, and then the horses are offered for adoption.

"What the BLM is doing right now is completely against the spirit and the letter of this act, but nobody is stopping them," said Walker.

What Walker, who also photographs wild horses, is referring to is a string of recent roundups, including one ongoing right now in the southwestern corner of Wyoming. It’s a huge undertaking encompassing five different areas, and it's estimated to last weeks.

Brad Purdy, the spokesperson for the BLM, says this roundup is necessary because there are too many wild horses there for the land to sustain. However, there are voices saying that’s not necessarily the case.

Erik Molvar is an environmental biologist and director of the Western Watersheds Project, an organization that aims to improve public land management. He says the pressure that grazing done by domestic cattle and sheep is outpacing any damage to the land done by wild horses. He argues the number of wild horses the Wyoming land can sustain is actually more than the BLM’s numbers show.

"Right now, the wild horses are about four times that appropriate management and yet still the land is meeting the thriving natural ecological balance, which calls into question whether that appropriate management level has anything to do with a thriving, natural ecological balance at all, or whether what it really set at is to keep the wild horse populations low so they can have more domestic livestock out there," said Molvar.

State governments have stepped up with concern about roundups. At the end of August, Colorado Gov. Jared Polis wrote to the US Department of the interior that he is “extremely concerned” with the rate of the roundups and called for a six-month moratorium on them for the American public to weigh in.

Another issue Walker has is what happens to the horses after they're rounded up. Right now, 50,000 horses are in long-term holding, waiting to be adopted. There's an incentive program that gives up to $1,000 to anyone who adopts an untrained wild horse.

Walker is currently a plaintiff in a lawsuit against this practice, saying folks are taking the money and then selling the horses to auction where they could be killed.

"What I would ultimately like to have happen is an investigation into the BLM and to have them removed as the managers of these wild horses," she said.

Purdy said that while the area where the Wyoming round up is occurring is near private grazing land, the decision to remove horses is based solely on there being too many, saying quote, “BLM would be gathering horses regardless of the land patterns or ownership of the private lands as required by the Wild Free-Roaming Horse and Burro Act of 1971.”

Walker hopes more attention is brought to this issue, the more people stand up for America's mustangs

"If people aren't standing up strongly for them, aren't fighting for them, these horses are just going to disappear," she said, "and I don't want to have a library of photos of animals that have disappeared."