Donald Trump’s unexpected election victory has spurred environmental groups’ best fundraising campaign yet.

The Sierra Club has signed about 11,000 new monthly donors since the election, more than nine times the number for last December, its best month ever. Other environmental groups including the Environmental Defense Fund and Natural Resources Defense Council also report surges in giving because the Trump administration has vowed to ease environmental regulations.

The bounty for environmental groups is part of a growing movement to offset Trump’s agenda through philanthropy. After the election, HBO comic John Oliver called for donations to organizations including Planned Parenthood and the investigative-journalism nonprofit ProPublica, resulting in a groundswell in support.

“I’m the fundraiser, so I’m usually the person initiating the conversation,” Mary Nemerov, Sierra Club’s chief advancement officer, said in an interview. “Right now, donors are reaching out to us to initiate that conversation.” The group has received about $3 million in post-election commitments.

With Trump talking about opening new areas to oil drilling, Sierra Club Executive Director Michael Brune said this is “the greatest assault we’ve ever faced on wildlife and wild places,” in a fundraising e-mail Wednesday evening. Lobbyists for the biggest oil companies are “already licking their chops at the promise of unfettered access to pristine wild places and coasts.”

The Environmental Defense Fund raised $250,000 online in the week following the election. That’s about double the amount during the same week a year earlier. About half were new members.

“The giving season seems to have started a little early for us,” said Sam Parry, the Environmental Defense Fund’s director of membership. “It’s not necessarily our core members; it’s their friends, their family, that may be a little more engaged.”

During more than 500 days on the campaign trail, Trump questioned climate science, said he would pull the U.S. out of the landmark Paris climate accord and promised to buttress the sagging coal industry. Spokesmen for the Trump transition team didn’t reply to an e-mail seeking comment Wednesday.

Neither the Sierra Club nor the Environmental Defense Fund expected Trump to defeat Hillary Clinton, who had led in the polls. The Environmental Defense Fund didn’t start drafting a formal fundraising e-mail “until the results came in,” Parry said.

The Sierra Club’s Nemerov was surprised to learn her director of online fundraising had written a “Plan B email” at a “low moment” the Sunday night before the election. The group sent out its first post-election fundraising email the afternoon following the election.

David Goldston, director of government affairs for the the Natural Resources Defense Council, expects donations to continue rising if Trump attempts to roll back regulations to curb pollution.

“At the point when environmental protection is most visibly under attack, people tend to rise to the challenge,” Goldston said.