The changeover comes as the diversified group faces a deluge of problems including stifling debt, U.S. litigation alleging harm from a weed-killer, a major drug development setback, weak agriculture markets and investor pressure to separate or sell businesses.

Ubben, who is a member of Bayer's sustainability council, has been among a number of investors who have long urged the company to consider a break-up, but he has kept a low profile.

Bayer CEO Bill Anderson, who was appointed last year after several investors including Ubben pushed for his predecessor to be ousted, has said he was thoroughly reviewing the group's structure and strategy.

"As an internationally renowned investor, Jeffrey Ubben will significantly enrich our work on the Supervisory Board thanks to his many years of experience in financial and capital markets," Bayer Chairman Norbert Winkeljohann said.

Ubben in November shut down Inclusive Capital Partners three years after starting the firm designed to focus on social investing.

The closure came as hedge funds struggled to raise new cash, and as a number of prominent investors were wrong-footed by markets amid interest rate moves and geopolitical turmoil.

In a separate statement, Bayer said the head of its consumer health business Heiko Schipper would be replaced by Julio Triana, currently running the pharmaceutical unit's commercial operations for the international region.

Schipper will leave the company on April 30 for an outside career opportunity, the company said. He joined in 2018 and was widely credited for boosting sagging earnings at the maker of Claritin allergy relief, and pain killers Aspirin and Aleve.

Some investors have urged a sale of the business to cut Bayer's debt load and to focus at problems at the pharmaceutical and agriculture units. CEO Anderson is due to update investors on his strategic review next week Tuesday.

Biotechnology expert Nancy Simonian and litigation expert Lori Schechter were also proposed to run for board seats in a shareholder vote at Bayer's annual general meeting on April 26.

(Reporting by Ludwig Burger; editing by Matthias Williams, Rachel More, Tomasz Janowski and Jan Harvey)

By Ludwig Burger