President Obama celebrated the 100th anniversary of the National Park Service Saturday, reminding people of the threat climate change poses to the historic outdoor spaces.

"As president, I'm proud to have built upon America's tradition of conservation. We've protected more than 265 million acres of public lands and waters – more than any administration in history," Obama said, before adding these efforts are not enough to sustain the nation's 400 parks and other sites.

"As we look ahead, the threat of climate change means that protecting our public lands and waters is more important than ever. Rising temperatures could mean no more glaciers in Glacier National Park. No more Joshua Trees in Joshua Tree National Park. Rising seas could destroy vital ecosystems in the Everglades, even threaten Ellis Island and the Statue of Liberty," Obama added.

The president encouraged Americans to take part in the administration's "Find Your Park" initiative, which connects the public to the park that's right for them. Under first lady Michelle Obama and Jill Biden's Joining Forces initiative, military families are eligible for free passes to any national park. In addition, the "Every Kid in a Park" program allows families with children in the fourth grade to get in to the parks for free.

Obama and his family visited Yosemite National Park and Carlsbad Caverns in June as part of the centennial celebration.

But for all of the praise Obama lavished on the parks, the president himself has not always been praised by Congress for seizing land and appropriating it for national spaces.

Obama has overseen the acquisition of 3.66 million acres of new federal land since 2009 with 19 new national monument declarations. The administration is considering placing several millions acres of western land under federal protection as national monuments during Obama's final months in office.

In April, the president designated nearly 2 million acres of California desert as national monuments. The administration also designated new monuments to Cesar Chavez in California, the Pullman Porters in Chicago, and activists who fought for equality at Stonewall in New York.

A coalition of lawmakers responded with the Protecting Local Communities from Executive Overreach Act to change the law the administration uses to make the declarations.

Critics of the land acquisition also have questioned how the National Park Service can manage more property when it already has a $12 billion maintenance backlog.

But National Park Service Director Jonathan Jarvis bashed a clause added to the Republican Party platform last month that advocates moving public land, especially in the West, to the states, saying the states are even more cash-strapped than the park service.

In his Saturday address, Obama pointed out some of the costly improvements the Park Service will see over the coming months as part of the anniversary celebration.

"We're revitalizing a grove of giant Sequoias in Yosemite; repairing the Lincoln Memorial; and enhancing the iconic entrance to our first national park at Yellowstone," Obama said.