SAN FRANCISCO — David Brower, who transformed the Sierra Club from a small hiking group into a political powerhouse during his nearly 70 years of environmental activism, died of cancer at his Berkeley home. He was 88.

Brower, who died Sunday, became the club's first executive director in 1952, when it had 2,000 members. When he left in a dispute with the board in 1969, it had 77,000 members. It now has more than 600,000 members and substantial influence in Washington and state capitals.

Bower also founded other groups, including the League of Conservation Voters.

"The world has lost a pioneer of modern environmentalism," said Sierra Club President Robert Cox. "Like the California redwoods he cherished, David towered above the environmental movement and inspired us to protect our planet."

President Clinton, who has created or expanded national monuments covering about 4 million acres in the West, called Brower "one of the earliest and most ardent defenders of the extraordinary natural heritage that enriches and unites all Americans."

"Over more than half a century, from Cape Cod to the Grand Canyon to the Alaska wilderness, he fought passionately to preserve our nation's greatest national treasures," Clinton said. "His fiery activism helped build and energize the modern environmental movement, rallying countless people to the defense of our precious planet."

Brower was an avid mountain climber and skier who dropped out of college as a sophomore after studying butterflies. He served in the 10th Mountain Division during World War II and had an outdoor adventure career that took him around the globe.

Brower joined the Sierra Club in 1933 and led efforts to pass the Wilderness Act, block construction of two hydroelectric dams in the Grand Canyon and create Kings Canyon, North Cascades and Redwoods National Parks, as well as Point Reyes and Cape Cod National Seashores.

"No words here can adequately express our loss, nor the overwhelming influence he and his conservation activism have had on the environment," Interior Secretary Bruce Babbitt said. "He was a tremendous force for nature and his accomplishments made him a well-respected visionary."

Brower, who persuaded skeptical Sierra Club board members to go ahead with expensive but successful coffee-table books of Ansel Adams' nature photographs, was forced out as executive director by board members unhappy that he made major decisions without consulting them.

He went on to found Friends of the Earth and the League of Conservation Voters, which have become respected environmental groups. He resigned from the board of Friends of the Earth after a battle for control in 1986. He also founded the Earth Island Institute.

"David Brower was the greatest environmentalist and conservationist of the 20th century. He was an indefatigable champion of every worthwhile effort to protect the environment over the last seven decades," said Green Party presidential candidate Ralph Nader.

Brower gave up on attempts to halt the construction of a dam in Glen Canyon, Ariz., to concentrate on stopping dam construction in Dinosaur National Monument, Colo. That trade-off haunted him, said his son, Ken Brower.

"Glen Canyon was what he considered his biggest mistake and the worst loss that happened on his watch," he said. "It ate at him considerably and it became an object lesson that he taught, which was 'Don't compromise.' "

Brower resigned from the Sierra Club board this past May — the third time in the past 15 years he had done that — to underscore his contention that leaders weren't doing enough to save the Earth.

"The world is burning and all I hear from them is the music of violins," Brower said. "The planet is being trashed, but the board has no real sense of urgency. We need to try to save the Earth at least as fast as it's being destroyed."

John McPhee, who wrote about Brower in his 1971 book "Encounters with the Archdruid," said Brower "listened to his own drum."

"He had some arrogance. He was feisty. He was a battler," McPhee said. "He was ministerial in the sense that he had a cause and he was in a pulpit."