With Harry Reid departing as the Senate's most powerful Democrat, environmental groups are applauding his green record, mourning the loss of a key ally, and watching warily for who will take his place.

While Reid may not highlight environmental priorities as much as some of the most progressive members of his party, he has unquestionably used his position of power to call for action on climate change, push clean energy, and criticize the Keystone pipeline.

Chuck Schumer, a top strategist for Senate Democrats and the front-runner to succeed Reid, has not made climate change a heavy focus of his work in the Senate even as the topic has moved to the top of the green movement's agenda.

The New York Democrat, who leads the Democratic Policy and Communications Center, has focused more heavily on economic policy, immigration, and other topics, and he doesn't sit on the Senate's Energy or Environment committees.

RL Miller, cofounder of the super-PAC Climate Hawks Vote, said Schumer has shown only "sporadic acts of leadership." Miller named several other Democrats whom some in the movement would prefer to see lead the caucus in a "perfect world." Those included: Hawaii's Brian Schatz and Rhode Island's Sheldon Whitehouse, both of whom have been out front in discussing climate change.

Although Schumer has not focused as heavily on the areas of highest concern for environmentalists, he has been a reliable vote in environmentalists' favor when those issues come up. He boasts a 91 percent lifetime score from the League of Conservation Voters (higher than Reid's mark of 80). He has also backed green-energy tax credits from his perch on the Finance Committee and repeatedly pushed for repeal of oil industry tax breaks. Schumer also took part in the big climate change march in New York City last September.

The question now is whether Schumer would—should he lead Democrats' Senate caucus—make those issues central to the party's agenda.

During his tenure in the Senate, Reid—who announced Friday that he is not running for a sixth term in 2016—has built up what environmentalists describe as an impressive track record on green priorities. While serving as majority leader, Reid helped to tpass a stimulus package that doled out $80 billion in clean-energy investments and to negotiate an extension of a tax credit that has been crucial to the growth of wind power as part of the fiscal-cliff deal.

Reid also blocked a vast array of bills that would roll back what green groups say are key environmental protections from advancing to the Senate floor. "He played environmental goalie and blocked every dirty shot by John Boehner," said Daniel J. Weiss, a senior vice president for campaigns at the League of Conservation Voters.

Reid is no fan of the Keystone XL pipeline and fought relentlessly to block nuclear-waste storage at Yucca Mountain in Nevada, an effort that has met with praise from environmentalists who oppose the plan favored by Republicans.

For the better part of the past decade, Reid has also played host to the Clean Energy Summit in Las Vegas, an annual event that he founded to shine a spotlight on clean energy in his home state and promote more aggressive national policies. The event draws big names in the green world, including Hillary Clinton last year.

"Environmentalists will be losing a major ally with Senator Reid retiring," said John Coequyt, Sierra Club's director of federal and international climate campaigns. "The environmental community has applauded his legacy and looks forward to other leaders stepping up and filling his shoes."

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