The of a dune is characterized by a decrease in energy and sand avalanches, which occur due to oversteepening

Dunes move over time with the wind as sand grains climb the windward slope of the dune until they are pushed it the leeward side where they slip down the lee slope. And it is called Leeward Side. leeward sides of the mountains has lost much of its moisture making these regions much drier. 

humans are now responsible for causing changes in the environment that hurt animals and plant species. we take up more space on earth for our homes and cities. we pollute habitats. human activity often changes or destroys the habitats that plants and animals need to survive.