"Ozymandias" describes a statue, and statues are made from rocks and stones found in nature. While the poem explores the way in which art necessarily involves some kind of engagement with the natural world, it also thinks about how nature might fight back. The statue's head is half-buried in the sand, after all, and we are left wondering what role the erosive force of dust storms, wind, and rain played in its destruction.
"Ozymandias" suggests that the relationship between art and nature is a double-edged sword: while the natural world furnishes the artist with raw materials, it also has the power to reclaim those materials by later destroying the work of art.