If you take a walk through Eugene’s parks or along the Willamette River, you might notice the lush greenery — thick blackberry brambles, fields of white flowers and ponds buzzing with life. But underneath all that beauty, a quiet crisis is unfolding.

Invasive plants and animals are spreading throughout Eugene’s natural spaces, pushing out native species and unraveling the ecosystems that have supported Oregon’s wildlife for centuries. From thick pastures overrun with blackberries to wetlands gnawed by giant rodents, the landscape is changing — and not for the better.

Tom Kaye has seen it up close. “Right now I’m driving through enormous fields of blackberry and Scotch broom,” Kaye, the chief scientist and founder of the Institute for Applied Ecology, said. “Large, large areas of land are now no longer quality habitat.”

Kaye started the Institute back in 1999 with a mission: to conserve native species through hands-on restoration, research and education. Today, his nonprofit works across the Willamette Valley — including right here in Eugene — helping city agencies and volunteers fight back against the green tide.

The invaders are relentless. In Eugene’s grasslands, common enemies like oxeye daisy — with its cheerful white blooms — smother native wildflowers, creating a monoculture that leaves little room for pollinators and wildlife. Meanwhile, warming temperatures are giving an extra boost to aggressive annual plants, which Kaye says are increasing by about 15% each year.

Animals are part of the problem too. Nutria, invasive rodents that look like a cross between a beaver and a rat, tear up wetlands as they feed. Bullfrogs, described by Kaye as “voracious predators,” gobble up everything from fish and ducklings to other frogs and lizards — even carrying diseases that decimate native amphibians.

Then there are the threats still looming on the horizon. “We really don’t want zebra or quagga mussels here,” Kaye warned. These tiny mussels, if introduced, could clog hydroelectric dams and devastate freshwater systems.

What’s at stake isn’t just a few plants or ponds. It’s the health of Eugene’s entire natural system. “Invasive species simplify our ecosystems,” Kaye said. “They reduce biological diversity and create dominance — the same species repeated over and over.” Without that diversity, wildlife struggle to find food, shelter and places to raise their young.

Restoration teams are fighting back with everything they’ve got — using controlled burns, mowing, hand-pulling weeds, spot-spraying and even laying down sheets of plastic to trap heat and kill unwanted plants. “Sometimes we’re restoring from scratch. Other times we’re tipping the scales in favor of native plants on sites with mixed vegetation,” Kaye said.

The best results come from combining treatments. “Burning alone doesn’t meet our needs, but combining burning with spot spraying can make a huge difference,” he said.

But even the best tools have their limits. Recent federal funding cuts have squeezed the resources available for restoration work. “That’s going to drastically reduce the impact we can have,” Kaye said.

And even when invasive plants are cleared, another challenge remains: finding enough native seeds to replant the land. “When you kill a weed, you want to replace it with something better. But where do you get those native seeds?” Kaye said. Without them, invasive species often just creep back in.

To fill the gap, the Institute works with the Willamette Valley Native Plant Partnership, teaming up with about 30 organizations and local farmers to grow seeds specially adapted to Oregon’s ecosystems.

Looking ahead, Kaye and his team are thinking long-term — studying what seeds already lie dormant in local soils, testing new ways to control stubborn plants like the seemingly indestructible Italian arum and even experimenting with “assisted migration,” growing Oregon plants alongside California plants to see which will thrive under future climate conditions.

Still, Kaye believes the battle won’t be won by scientists alone.

“Start thinking locally,” he said. “What can you do in your yard? Are there weedy areas you can control and replace with native plants? You’ll help pollinators, help wildlife and make your yard more beautiful.”

In Eugene, the fight for biodiversity is happening one field, one riverbank and one backyard at a time. And for now, there are still plenty of reasons to stay in the fight.