VIDEO: President Obama speaks at Yosemite National Park

YOSEMITE NATIONAL PARK, Calif. -- President Obama commemorated the 100th anniversary of the National Park system in Yosemite Valley.

He said climate change is the biggest threat to U.S. national parks. He also added meadows are already drying out at Yosemite National Park in California, where he spoke Saturday after spending the night in the park with his wife, Michelle, and daughters Malia and Sasha.

Obama said that a rabbit-like animal known as a pika is being forced further upslope in Yosemite to escape warming temperatures.

Obama and his family are spending the weekend at Yosemite after touring an underground cave Friday at Carlsbad Caverns National Park in New Mexico.

He wants more people to appreciate and visit America's national park as the system nears its 100th birthday in August.