university of maryland scientists project large portions of the national park will be underwater by the year 2050 if planet warming emissions are not drastically curbed. rising tides threaten places like this cemetery for freed black people in tubman s community. these low-lying areas that were a part of the important trails that allowed people to escape at that time will be lost in some places. reporter: more than 70% of national parks in the continental u.s. are at high risk from the effects of climate change. from sea level rise and flooding to extreme temperatures, drought and wildfires. historic flooding at yellowstone national park last month forced it to shut down for more than a week. california s hesequoia national park, home of the world s largest trees, wildfires have burned large swaths of the giant sequoia growths.