Is earth mantle part of the biosphere why or why not scientists want to protect the beach from erosion what can they do

The answer is; NO. The biosphere is part of the earth where life exists. These include the upper portions of the crust called the pedosphere, the hydrosphere and the lower atmosphere. The mantle is found below the crust and the conditions are not conducive for any life form.

They can build a seawall around the beach or breakwater barriers. These manmade structures are meant to break the powerful waves that eat into the coastline. They mitigate the rate of the erosion but cannot prevent it completely.