After his father's death in 1971, his mother married Dr. André Frédéric Cournand, a physician who was awarded the Nobel Prize for medicine in 1956.

[4] After graduating from Harvard, Berle joined the United States Air Force where he trained as a parachutist and intelligence officer.

Con Ed planned on building a pump storage facility on a hillside overlooking the Hudson River but Berle and the firm won a precedent-setting victory that forced the company to fix any environmental damage.

[27] During his tenure, action was taken against the General Electric Company for discharge of PCBs into the Hudson River and his office was responsible for readying and running the venues at the 1980 Winter Olympics in Lake Placid.

[34] Concurrently, he was the president of the Stockbridge Land Trust, director of the Orion Society and a trustee and former chairman of the Century Foundation.

[35] As president, he worked to prevent oil drilling in the Arctic National Wildlife Refuge as well as arguing before the Supreme Court in support of responsible handling of water issues in the Midwest.

[17] In 1993, he was one of the five U.S. members appointed by President William J. Clinton to the Joint Public Advisory Committee, a constituent piece of the Commission on Environmental Cooperation under the North American Free Trade Agreement, serving until 2002.

Peter and Lila were the parents of:[35] Berle died on November 1, 2007, in Pittsfield, Massachusetts[2][13] of injuries sustained in August 2007 in Stockbridge when the roof of a barn collapsed as he was dismantling it.