The American Civil Liberties Union has lost a quarter of its yearly donations after a major donor cut off $19 million in annual donations because of economic difficulties.

David Gelbaum, a wealthy California conservationist, said he was indefinitely stopping the donations that had made him the New York-based group's largest anonymous donor.

"For a number of years, your organization has received very substantial charitable contributions from me," Gelbaum said in a statement. "My investments in alternative, clean energy companies have placed me in a highly illiquid position as a result of the general credit crisis in the American and world financial systems."

Gelbaum also announced he was halting some $12 million in yearly gifts to the Sierra Club Foundation and about $50 million a year that he's been giving to an organization serving veterans who served in Iraq and Afghanistan. Gelbaum has given a total of $389 million to the groups from 2005 to 2009.

The New York Times named Gelbaum in a story published in the newspaper Wednesday. Gelbaum had previously funded those organizations anonymously.

"While we're clearly disappointed that his desire to remain anonymous was breached, we remain eternally grateful for everything he and his family have done to advance the cause of civil liberties for all Americans," ACLU Executive Director Anthony D. Romero said.

Romero also called Gelbaum an American hero, "an unassuming man with a spectacularly generous spirit."

Gelbaum says he hopes others will step forward and replace his donations.

Gelbaum, a native of Minnesota, once chaired the math department at the University of California, Irvine. He made his fortune working for hedge funds, where he used mathematical formulas to pick stocks and bonds.

He runs an investment firm called Quercus Trust, based in Newport Beach, Calif.