paul labovitz is the park's superintendent. >> we continue to be one of th most biologically-diverseces in the national park system, and in north america. a couple miles from here, i can take you to a place where there's prickly-pear cactus growing next to bearberry, which is an arctic plant, side by side. >> reporter: the most eye- catching feature of the park is the sand dunes that have run through the area for more than 10,000 years. they are the product of a natural process called erosion, when outside forces transport rock and soil from one place to another. >> the sand dunes you see here are the product of water and wind over time, eroding sandstone into smaller and smaller particles, and then that sand moving around with wind and ter. the grand canyon is a product of erosion. the badlands is a product of erosion. it's really kind of a cool thing to think about, d it's not necessarily a bad thing. >> reporter: but over the last few years, erosion along the dunes and in the surrounding area has increased in speed and intensity. >> four years ago, we would have been under 20 feet