Henderson Island, covering about 86% of the territory's total land area and supporting a rich variety of animals in its nearly inaccessible interior, is also capable of supporting a small human population despite its scarce fresh water, but access is difficult, owing to its outer shores being steep limestone cliffs covered by sharp coral. In 1988 this island was designated as a UNESCO World Heritage site.[23] The other islands are at a distance of more than 100 km (62 mi) and are not habitable.