Disadvantages of cutting down trees are: 
It destroys animal habitats, decreases amount of oxygen in atmosphere, destroys plants that may be cures for diseasesTrees give us oxygen, it will be like cutting off oxygen supply.. The organisms that live around it will perish.It ruins the beauty.It will take away the shelter they provide for birds and other animalsIt will ruin life cyclesLess CO2 would be used up by trees = Less oxygen to be produced = Global warming speeds up = Many animals lose their homes; thus their lives = Our universe will become meaningless eventuallyWithout trees, there will be flooding as trees can soak up to 1,000 gallons a day. Without trees, there will be very little to soak up carbon dioxide and cleanse the air. Without trees all species depending on it would become extinct. Without trees, the climate would heat up faster as there will no natural "air-conditioning."An animal's habit can be lost and the animal may become extinct.
Cutting Trees causes loos of habitat for birds and animals. Trees provide oxygen, which humans and other organisms breathe in. Fruits provided by trees are nutritious like apple tree. Trees  provide many medicines. In mountainous regions, trees hold the soil together, which cause soil erosion. Cutting down of trees and forests is one of the main reasons for animals like the tiger becoming extinct.