The fate of nascent government efforts to combat climate change hangs in the balance following the recapture of the Senate by Republicans, environmental activists fear.

By wresting control of the chamber from Democrats and tightening a grip on the House of Representatives through a succession of victories Tuesday, the GOP has put itself in a stronger position to block or roll back White House legislation.

And green campaigners worry that climate-friendly regulations, including those aimed at reducing greenhouse gas emissions, could be targeted by the resurgent Republicans.

The political power shift comes despite efforts by wealthy environmentalists to counter the impact of money from conservative groups. Billionaire climate activist Tom Steyer’s political action committee reportedly spent $65 million on the midterm elections to highlight the importance of voting for climate-minded leaders. Steyer spent $50 million of his own money on political ads, including one featuring Hollywood actor Woody Harrelson, in an effort to reach voters.

The campaign by NextGen Climate was focused on Colorado, Michigan, New Hampshire and Iowa — races viewed as critical to maintaining a Democratic majority in the Senate. But in major races, the cash injection did not sway Republicans on environmental protection.

Exit polls on Tuesday showed a stark divide along partisan lines on climate change, with 71 percent of Democrats responding that they thought global warming was a serious problem, versus just 27 percent of Republicans, The New York Times reported.

With control of the Senate, Republican will be able to appoint the chair of the Environment and Public Works Committee, which controls the Environmental Protection Agency. On the campaign trail, Sen. Mitch McConnell, who won his re-election bid Tuesday and is likely to become Senate majority leader, promised to cripple the EPA’s ability to regulate carbon emissions of power plants. Now he could have the tools to at least hamstring the federal agency.

In Colorado — a state with more than 50,000 active oil and gas wells — Republican Cory Gardner was projected to take the Senate seat from incumbent Democratic Sen. Mark Udall on Tuesday night, though the governor’s seat remains too close call.

“Gardner doesn’t believe climate change is real and is running a campaign based on anti-science,” Gary Wockner of the environmental organization Clean Water Action, told Al Jazeera.

The race for Colorado governor would be “neck and neck,” Wockner said, with incumbent Democratic Gov. John Hickenlooper, who has said he believes humans are contributing to climate change, running against Republican challenger Bob Beauprez.

“Beauprez is rabidly pro-drilling and doesn’t believe in climate change,” Wockner said. Election results early Wednesday morning put Beauprez ahead of Hickenlooper by 1 percentage point.

Fracking — an oil and gas extraction process through which sand, water and chemicals are pumped into the ground to release trapped fuel deposits — has grown significantly over the last 25 years, with the number of active fracking wells doubling from 1990 to 2009.

Before Tuesday’s election, Senate Republicans on the Environment and Public Works Committee released a report saying fracking was fueling an “energy renassiance.” The Senate Republicans, who will now constitute a majority on the committee, said “decades of studies” have shown the process to have minimal impact on the environment.

But critics say fracking’s largely unregulated development poses pollution and health risks. Residents in five Colorado cities had put fracking bans on the ballot for Tuesday, but the initiatives were struck down by district court judges in August. The decisions called such bans illegal after the oil and gas industry sued the cities.

“Everyone involved in the fracking bans was extremely disappointed that the ballot initiatives were pulled off,” Wockner said.

In Michigan, Green Party Senate candidate and environmental activist Chris Wahmhoff ran on a simple platform — stopping Alberta-based energy company Enbridge from expanding an aging tar-sands pipeline that runs underneath the Straits of Mackinac, where Lake Huron and Lake Michigan meet.

With control of the Senate, many expect Republicans to try and force President Obama to approve the larger Keystone XL pipeline, which would carry tar-sands from Canada to Texas.

Though Wahmhoff, who grew up on Michigan’s Kalamazoo River, which was contaminated when a different pipeline ruptured, trailed behind the mainstream candidates — overall projections put him at around 1 percent — in select districts he fared better, with exit polls indicating he won 15-20 percent of the votes. The race is expected to be won by Democratic candidate Gary Peters, who was up by around 10 percentage points on Rep. Terri Lynn Land on Tuesday night.

Speaking to Al Jazeera on the way to a campaign party hosted by the Green, Socialist, Libertarian and Taxpayers parties, Wahmhoff said he was happy with his race and hopeful that the Greens would be working more closely with the other third parties in the future.

“If there was no other reason to campaign but getting awareness, and using it to promote a good cause, then it’s just amazing,” Wahmhoff said. “And the third parties here in Michigan are working on a coalition … and consolidating other efforts.”