The Importance Of Trees. We could not exist as we do if there were no trees. Trees produce the very oxygen we breathe. They provide shelter for us and wildlife. They absorb carbon dioxide and intercept other pollutants helping to clean the air. The main reason many animal species are endangered is deforestation.The importance of forests cannot be underestimated. Reversing deforestation fronts will require a concerted effort by Policymakers. Photo taken in St. Louis County, Missouri.