The geography of New York City is characterized by its coastal position at the meeting of the Hudson River and the Atlantic Ocean in a naturally sheltered harbor. The city's geography, with its scarce availability of land, is a contributing factor in making New York the most densely populated major city in the United States. Environmental issues are chiefly concerned with managing this density, which also explains why New York is among the most energy-efficient and least automobile-dependent cities in the United States. The city's climate is temperate.