Complex sentence: Seedlings need to be protected from human trampling and this is done mainly by fencing off newly planted areas, fencing also acts as another way of trapping and accumulating sand among the dunes and can also act as protection against strong winds.
Split into simpler sentences: Seedlings need to be protected from human trampling which is done mainly by fencing off newly planted areas. Fencing also acts as another way of trapping and accumulating sand among the dunes and can also act as protection against strong winds.