Write a poem about something that can’t be seen, but that is present, in some shape or form, everywhere on earth.
Perhaps you'll write about something as tangible as oxygen, as elusive as love, or as persistent as hunger. Perhaps your poem will reflect the state of the world, our common challenges, our interconnectivity, or our abiding hope.
As you craft your piece, keep in mind that just because it's a poem it doesn't have to rhyme. You could use free verse, or you could even set your poem to music. If you decide to write a particular type of poem (such as a sonnet or ballad, for example), the Poetry Foundation has a great list of the many different forms of poetry here.
Finally, remember that sometimes poetry uses an impression or metaphor or sketch of an idea rather than explaining something in concrete detail. Can you "sketch" your ideas for your reader?