Golding clearly sees the natural world of the island as the backdrop against which the boys regress from civilized behavior into chaos. The harshness of nature is presented throughout the novel. However, it is not the natural world (nature) per se that propels the boys' descent into anarchy; it is human nature that accomplishes this regression.
The boys' savagery is what renders the depictions of natural phenomena into something other than neutrality. For instance, the conch shell is, by itself, a beautiful object. The boys adopt the conch as their symbol of authority; whoever holds the conch "has the floor," so to speak. They don't see the beauty of the seashell. They see only the opportunity to impose some order, and later they see it as the means by which to control others.
Golding seems to say that in a natural state, absent rules and laws, humans will revert to savagery. What better laboratory for Golding to explore his thesis than an uninhabited island, devoid of adult supervision?