He served as minister of environment and protection of land and sea from 1996 to 2000 in three different cabinets.

[1] In 1989 he was elected to the European Parliament, but resigned from office after serving in the post just for one month to concentrate on his initiative, namely Rainbow Greens, which he had cofounded with Francesco Rutelli earlier in 1989.

[4][8] However, Ronchi's proposal was not endorsed, and Willer Bordon replaced him as minister of environment.

[4][8] When Ronchi was in office as environment minister Italy signed the Kyoto Protocol in 1997.

[6] After leaving public office, Ronchi began to work at the Sustainable Development Foundation, and as of 2013 he was on the national advisory board of Ecomondo, an initiative for green movement.