Explain the poem "Possum Crossing" by Nikki Giovanni?

Sometimes it's a mistake to try to impose "deeper" meaning on a poem. When you say that the message of the poem is "we should all treat each other with respect because we all share this world," do you mean that the poem is about how we human beings should treat each other? If so, I think you're trying to force a meaning onto the poem that isn't supported by the text. The poem isn't about social relationships among human beings. The only thing the human speaker of the poem has to say about other people is that she'd like to put up a sign that would warn drivers to be more mindful of the animals who are in danger of being run over by their cars. If, when you say "we all share this world," you're talking about the fact that the human race shares the world with other species, then I think you're reading the poem accurately. The speaker talks about driving with care so that she won't kill animals in the street outside her house. She's obviously serious about the moral obligation she feels to respect the lives of other creatures, but she also acknowledges that violent death can be part of nature, not just something inflicted on the natural world by thoughtless humans. (Look at the image of a cat killing a mole.) And she seems to be mocking herself gently in the final lines, presenting herself as a slightly ridiculous figure who is so reluctant to run over small animals that she spills coffee as she brakes to avoid hitting "a big wet leaf."