In addition, deforestation affects watershed habitat, the runoff and filtering of groundwater, adds silt and erosion into streams, rivers and lakes, and removes the natural habitat of numerous species of animals, birds and insects that depend on the forest and jungle to provide them with food and shelter.  This disrupts the food chain and threatens the continued existence of other species.

Trees are a prime remover (along with the oceans) of CO2 and other greenhouse gases from the atmosphere, so deforestation speeds up the process of global warming and climate change.  It removes a renewable resource that, if sustainably harvested, can supply timber to economies indefinitely.

Lastly, deforestation adds to a phenomenon called desertification.  Sounds like I made that one up, but I didn't.  It can permanently alter local climates and the ecosystems they support, not to mention the human populations there.

For the world as a whole, the impact of deforestation on climate is indirect.  Forests are very good at taking carbon dioxide out of the air.  Plants use carbon dioxide in their respiration, taking it out of the air and putting oxygen in the air.  This means that execssive deforestation could lead to more carbon dioxide in the air and more warming.

It also seems that deforestation affects climate in less predictable ways.  This happens as deforestation affects precipitation patterns, even in places far from the deforestation.