This year’s Global Climate Action Summit in San Francisco got a boost of star power Thursday when activist and actor Harrison Ford took the stage to deliver an impassioned speech decrying climate change and anti-science political leaders. “If we can’t protect nature, we can’t protect ourselves,” Ford said in his remarks.

Ford’s speech touched on a number of issues, and offered a grim outlook for humanity should we continue to ignore climate change. “If we don’t change the path that we’re on today, the future of humanity is at stake,” a solemn Ford declared. He continued, addressing attendees directly: “While you work to meet the challenge of climate change, I beg of you—don’t forget nature. Because today, the destruction of nature accounts for more global emissions than all the cars and trucks in the world.”

At other points in his speech, which was posted on Twitter, Ford referred to climate change as a “monster” and encouraged everyone to “shut off [their] phones, roll up [their] sleeves, and kick this monster’s ass.”

The actor, of Star Wars and Indiana Jones fame, has been outspoken in his critiques of climate change deniers. He slammed the Trump administration while accepting an award from environmental nonprofit Conservation International last November.

“We face an unprecedented moment in this country. Today's greatest threat is not climate change, not pollution, not flood or fire. It's that we've got people in charge of important shit who don't believe in science,” he said during his 2017 acceptance speech, according to The Hollywood Reporter. He also criticized politicians who allow “political or economic self-interest denigrate or belittle sound scientific understanding of the causes and effects of human pressure on the environment.”

Ford took aim at the Trump administration again on Thursday, closing his speech with passionate remarks. “For God’s sake, stop electing leaders who don’t believe in science,” he exclaimed. Even worse, he said, are those who “pretend they don’t believe in science” for political motives. “Never forget who you’re fighting for,” he urged attendees.

Ford has been an ardent environmentalist for decades, but has recently stepped up his advocacy in the face of the Trump administration’s backwards approach to climate change and the environment. The president infamously withdrew the United States from the Paris Climate Accord, and his administration recently announced new “rules” for coal-powered plants. Even Trump’s EPA the new rules will cause more than one thousand deaths per year.

If only a plucky young starship pilot could team up with a Wookie, a young Jedi, and a space princess to free us from the clutches of Darth Vader and his evil empire.