Oil billionaire David Koch has resigned from the board of the American Museum of Natural History (AMNH) amid pressures from environmental advocates, who have urged the museum to cut ties with fossil fuel companies.

Koch, who is thought to be worth around US$43bn (€39.7bn, £30bn), has donated more than US$20m (€18.5m, £14m) to the museum during his 23-year tenure as a board member.

A spokesperson for the museum confirmed to AM2 that Koch’s position as a board member ended on 9 December, the date of the trustees’ annual meeting.

The Guardian is reporting that Koch’s resignation was not motivated by calls for his resignation from anti-oil protests, but a collective of activists and scientists – which gained national attention in 2015 with an open letter signed by dozens of prominent scientists calling for Koch’s resignation.

In addition to the letter, signed by several Nobel laureates, a petition calling for Koch’s resignation garnered more than 230,000 signatures, adding to pressure against the multi-billionaire.

Despite his resignation from the AMNH, Koch remains a part of the Smithsonian National Museum of Natural History advisory board and remains a major funder of the Metropolitan Museum of Art.