Ecologist Greta Wengert stared down the pockmarked hillside at a pile of pesticide sprayers left behind, long after the raid. Wild animals had gnawed through the pressurized canisters, releasing the chemicals inside.

“They’re just these little death bombs, waiting for any wildlife that is going to investigate,” said Wengert, co-founder of the Integral Ecology Research Center, a non-profit that studies the harms caused by cannabis grows on public lands. For all her stoic professionalism, she sounded a little sad.

For over a decade, Wengert and her colleagues have warned that illegal cannabis grows like this one dangerously pollute California’s public lands and pristine watersheds, with lasting consequences for ecosystems, water and wildlife.

Now, they’re sounding another alarm — that inadequate federal funding, disjointed communication, dangerous conditions and agencies stretched thin at both the state and federal level are leaving thousands of grow sites – and their trash, pesticides, fertilizers and more – to foul California’s forests.

Dozens of fertilizer bags wept blue fluid onto the forest floor. Irrigation tubes snaked across the craters of empty plant holes. The cold stillness felt temporary — as if the growers would return at any moment to prop up the crumpled tents, replant their crop and fling more beer cans and dirty underwear into the woods.

Wengert has tallied nearly 7,000 abandoned sites like this one on California’s public lands. It’s almost certainly an underestimate, she said. Her team knows of only 587 that have been at least partly cleaned up.

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No government agency can provide a comprehensive count; several referred CalMatters back to Wengert’s nonprofit for an unofficial tally.

Most of the sites Wengert’s team identified are in national forests, where “limited funding and a shortage of personnel trained to safely identify and remove hazardous materials” is driving a backlog in clean ups, a U.S. Forest Service spokesperson told CalMatters via an unsigned email.

The federal government, the spokesperson said, has dedicated no funding for the forest service to clean them up. And it’s leaving a mess in California.

Most of the sites Wengert’s team identified are in national forests, where “limited funding and a shortage of personnel trained to safely identify and remove hazardous materials” is driving a backlog in clean ups, a U.S. Forest Service spokesperson told CalMatters via an unsigned email.

The federal government owns nearly half of the more than 100 million acres in California. But it’s California’s agencies and lawmakers taking the lead on tackling the environmental harms of illegal grows— even as the problem sprawls across state, federal and privately managed lands.

The California Department of Fish and Wildlife’s policy is to clean up all grows spotted on its 1.1 million acres of wildlife areas, ecological reserves, and other properties, officials say.

Staff assist with clean ups on federal lands “when asked,” said cannabis program director Amelia Wright — typically on California’s dime. But, she said, “That’s not our mandate.”

Fees and taxes on California’s legalized cannabis market fuel state efforts — supporting the California Department of Fish and Wildlife’s cannabis program and funding tens of millions of dollars in grants for rehabilitating places damaged by cultivation. These grants can cover clean-ups and sustainable cultivation projects, or even related efforts like fish conservation.

The department has helped remove almost 350,000 pounds of trash and more than 920 pesticide containers from grows on public lands over nearly a decade.

But former Assemblymember Jim Wood, a North Coast Democrat, said that as he prepared to leave office in 2024, progress on clean ups was still too slow.

“It doesn’t reflect what I see is the urgency to watersheds, and the water and the people that are served by them,” he said.