People must make environment-friendly changes to their lifestyles and politicians must encourage those changes, activists said during a rally on the Boston Common on Saturday.

More than 2,000 protesters during the rally, one of more than 1,300 simultaneous demonstrations nationwide, recited a pledge to curb their own energy use and listened as local politicians pledged to help others do the same.

“It is up to every generation, but the voices of college kids and young people will be the energy behind this movement,” said U.S. Rep. Edward Markey (D-Mass.), who heads the House’s newly formed Select Committee on Energy Independence and Global Warming.

“We are either going to know each other or exterminate each other as a planet,” Markey added.

“Stepping up and speaking out is the key,” said Ross Gelbspan, a former Boston Globe editor. “You have to tell other people loudly and clearly why you are making these lifestyle changes.”

Gelbspan urged Congress to create “responsible” energy policies that would cut carbon emissions by at least an ambitious 80 percent by 2050.

“We are basically here today to reclaim our future,” he said. “Nature is telling us to cut our use of coal and oil by 85 percent not today, but yesterday.”

“We have made Mother Earth sick,” Boston City Councilor-at-Large Felix Arroyo said.

Erin Rowland, spokeswoman for environmental advocacy group StepItUp, said the Boston demonstration her group organized was one of the largest held Saturday.

“This rally had a lot of involvement from kids and gave them an opportunity to get involved,” she said.

At the start of the rally, children formed a chain and paraded holding decorated fish they had made from recycled materials. Many of the rally speakers focused their speeches on appeals to the nation’s youth.

Paul Epstein, associate director of the Center for Health and the Global Environment at Harvard Medical Center, said rallies like the one held Saturday reflect an increasing public awareness of global warming that may eventually translate into results once thought unreachable.

“With a comprehensive plan and lots of good incentives, we can make this change that is needed for better health and a healthy environment,” he said.

At the end of the rally, speakers led the participants in a pledge.

“I pledge to make saving our planet a priority, to waste less and share more of nature’s gifts and to do everything in my power to stop the climate crisis,” the crowd repeated.