senior editor craig miller sat down with national parks director jon jarvis to find out. >> jon jarvis, thanks for taking time with us. >> thank you. >> you and i first met last fall up in glacier national park. you were talking to a group of reporters on a creek. and you said the greatest threat to the integrity of the national park system that you've ever faced is climate change. that's a huge statement. >> i believe every bit of it. glacier national park is the perfect place to do that besides being a beautiful place. gra glacier is the poster child for climate change. based on predictive models we see, within a couple of decades, the glaciers that define glacier national park will literally be gone. glaciers store water. they provide a refrigerator service basically for free for streams that support wild trout and other species. all of that is going to change. the basic integrity for our national parks is being challenged by climate change. >> california has a huge stake in this. i think i counted more than 20 parks, monuments -- >> 25. >> 25. you know the exact number. joshua tree