SAN FRANCISCO — Saturday is Earth Day and things haven’t looked this bad for the environment in a long time, according to a former Republican congressman who helped launch the holiday.

Pete McCloskey, who co-chaired the original Earth Day celebration in 1970, said there’s little to celebrate this year as President Donald Trump and Republicans in Congress set out to slash budgets for environmental agencies and undermine laws that protect water, air and wildlife.

“This will be a black day. This will be a day of mourning for what is about to happen to environmental regulations,” said McCloskey, who represented parts of the San Francisco Bay Area in Congress from 1967 to 1983. “In 1970, it was joyous as millions of people turned out against air pollution, water pollution.”

The first Earth Day is credited with galvanizing public support behind sweeping changes to how the government managed natural resources. Months later, Congress created the Environmental Protection Agency. The Clean Air Act was also passed in 1970, while the Clean Water Act was passed in 1972. McCloskey co-authored the Endangered Species Act in 1973.

These hard-fought gains are in jeopardy, McCloskey told HuffPost. The White House’s budget proposal aims to reduce the EPA’s spending by 25 percent, while the National Oceanic and Atmospheric Administration’s budget would shrivel by 17 percent.

McCloskey pointed to a recent legal change allowing hunters to shoot hibernating bears in Alaska and worried that the Endangered Species Act would be dismantled.

While many federal agencies would get trimmed under Trump’s budget proposal, there would be spending increases for defense, homeland security, transportation and veterans affairs. Trump often describes his push to cut back environmental protections, such as fuel efficiency standards, as a way to clear obstacles for business and create opportunities for job growth.

“It’s a disaster and it’s going to set aside what we’ve accomplished since the first Earth Day,” said McCloskey, who registered with the Democratic Party in 2007 after becoming disillusioned with President George W. Bush’s administration.

During an Earth Day event organized by San Francisco Mayor Ed Lee (D) on Thursday, McCloskey made similar comments. In a statement, he urged voters to defeat California Republicans like Rep. Kevin McCarthy, the House majority leader, in next year’s elections and vote for candidates favoring conservation and climate change policies.

Thousands of scientists are planning to march on the National Mall on Saturday to protest what they see as Trump’s disregard for science and government funding for research.