Summarize the effects of human population growth and catastrophic events on ecosystems

With the ever increasing of human population over the years, it has taken a lot of toll on our ecosystems. There is a distinct difference between marine life, rivers, lakes, oceans, mountains and other animal habitat from today and a few years back. They have now become more barren and polluted. 

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i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.