Kauai, more than 5 million years old, is the oldest of the larger Hawaiian Islands. Waialeale Peak [5148 feet (1569 meters)], the wettest place on Earth, receives more than 500 inches (1270 centimeters) of precipitation each year. Because of excessive precipitation, much of the island (especially where humans and animals have modified the natural environment through agriculture and grazing) now faces the challenge of erosion. Gullied erosion has been documented along the Na Pali Coast of northwest Kauai where overgrazing has produced steep, barren slopes. The large quantity of rainfall has shaped beautiful vegetated canyons and valleys. Many conservationists are now studying the erosion problems to determine what balance can be maintained to protect and preserve the delicate flora and fauna species. The northeast half of Niihau is visible in the lower right corner of the photograph.