 O parks plays a particularly important role in conserving critical biodiversity in a section of the Mesoamerican Biological Corridor known as the Paso del Istmo, located along the 12-mile-wide isthmus between Lake Nicaragua and the Pacific Ocean., according to the United Nations Environment Programme, the United States had a total of 6,770 terrestrial nationally designated (federal) protected areas.These protected areas cover , or 27.08 percent of the land area of the United States.