Maybe you don't know the fact that the green forests we see from an airplane or from the highway can be false. Because centuries ago forests were twice as many as what they are today. A hike into many of those woods will tell different stories, too--of diseases and insects that are slowly killing trees, of some forests that are burned by fire, of logging that local people do more often. Deforestation  and degradation   of the world's forests mainly harm the basic ability of those ecosystems   to function or provide services, such as fresh water, air, plants and animals, which benefit people everywhere and keep the balance of nature.  Deforestation Forests today are a small part of what they once were. Nearly half of the world's forest cover is gone, and each year 40 million acres more are cut and replaced by agriculture and development. Over the next 45 years, wood use in the world is guessed to increase by 50 per cent over its present rate. Many of the forests that remain are severely destroyed, which harms the ability to protect birds or wild animals, and to supply natural resources to people. Deforestation also brings about between 20 per cent and 25 per cent of all air pollution causing global climate change. Degradation Forests continue to be degraded by some uses such as the gathering of wood for fuel, the arrival of pests and diseases that kill trees, the effects of climate change and poor management such as the fire, flood and so on. What do deforestation and degradation of the forests mainly harm?
Fresh water, air, plants, animals and people. The ability of the ecosystems to function. The local people's life and their health. The scenery which benefits tourism.