[The Earth Says:]

Hashem's is the earth and its fullness,

the inhabited land and those who dwell in it.

(Tehillim 24:1)

And the verse says:

From the edge of the earth we have heard songs,

"Glory for the righteous"

(Yeshayahu 24:16)

The purpose of Creation is to establish the kingship of G-d in the world.  Just as the moon is barren and empty, so too the earth would be if G-d had not filled it with all that is needed for life and populated it with people and creatures. Why?  So that its inhabitants would recoginize that we are here to make the earth beautiful and use its goodness to cede it back to the One Who put us here.

When this is done then the Earth's Song is sung and fulfills the purpose of its creation.

-[Perek Shira, MeAm Lo'ez]