This movie demonstrates how humans utilize nature as a disposable waste and instead of realizing it's a finite source. Bee Movie displays this on a smaller scale as the main problem in the movie is that humans can just buy honey right off grocery store shelves instead of working for it. Not only does this movie address the bigger issue of humans' selfish acts of non-conservation, but the fact that we as a population take nature for granted and what we don't realize is how beautiful and graceful nature can really be. Shameful as it is we can not comprehend that it is right outside our door step.
"Heaven is under our feet" the underlying message here is that nature is so glorious and elegant it can be compared to Heaven. As a nation that dominantly believes in Heaven and afterlife, we can not seem to understand that part of Heaven is right at our toes, the soil itself is a beautiful thing.
The Importance of Nature is what can put human back into humanity if we just realize that it is such a beautiful and pure element. What Thoreau is explaining through this quote is that nature is so easily accessible, but we are to shrewd and selfish to realize something right underneath our feet.