Trees absorb carbon dioxide during the process of photosynthesis and release oxygen which we need to live. Those that grow on river banks reduce erosion and flooding. A treeless environment would not only be a great loss to all the birds, animals and insects that rely on trees but a very strange world. They do beautify the landscape and provide an environment for breeding and feeding for a diversity of wildlife. The shade in summer that is created by large trees reduces the cost of air conditioning whereas they slow the cold winds in winter and this saves heating costs.