Yale School of the Environment (YSE) is a professional school of Yale University. It was founded to train foresters, and now trains environmental leaders through four 2-year degree programs (Master of Environmental Management, Master of Environmental Science, Master of Forestry, and Master of Forest Science), two 10-month mid-career programs, and a 5-year PhD program. YSE strives to create new knowledge that will sustain and restore the health of the biosphere and emphasizes the possibility of creating a regenerative coexistence between humans and non-human life and the rest of the natural world. Still offering forestry instruction, the school has the oldest graduate forestry program in the United States.