One of the major contributions of Gadgil is his effort towards the preservation of ecology of India. His early researches in the 1980s have helped in the identification of the Nilgiris as the first biosphere reserve in India. As the chairman of the Western Ghats Ecology Expert Panel (WGEEP), which later came to be known as the Gadgil Commission, he submitted a report in 2011, marking around 64 percent of the Western Ghats region as Ecologically Sensitive Area (ESA). The report attracted support and dissension, the environmentalists welcoming the recommendations and the state governments of the neighbouring states and the Syro-Malabar Catholic Church of Kerala disapproving it. This paved way for the subsequent Kasturirangan Commission, which diluted the recommendations to a level more acceptable to the state governments. He has been credited by many with the introduction of quantitative investigations of ecology and animal behaviour in India and for including humans as a vital part of ecosystems. His contributions, as a member of the draft committee, has been reported in the preparation of the Biological Diversity Act 2002 and the manual he prepared for the People's Biodiversity Registers has been accepted by the National Biodiversity Authority. He is still associated with the Authority in the preparation of a biodiversity inventory at the local bodies' level.