(CNN) A San Francisco conservation group has kicked off a public fundraising campaign to buy and protect the world's largest remaining privately owned giant sequoia forest. It just needs $15 million.

Save the Redwoods League announced Tuesday that it has reached an agreement to purchase the 530-acre property, known as Alder Creek, from the current owners if it raises the funds.

The forest is home to some massive trees, including the world's fifth largest, known as the Stagg Tree.

And here's a fun fact: Giant sequoias are the third longest-lived tree species on the planet, the National Park Service says. (The oldest known tree was 3,266 years old .)

The property is about 200 miles from Los Angeles and is surrounded by the Giant Sequoia National Monument, the league said.

Read More