Environment

Ancient bristlecone pine forests are being overwhelmed by climate change

For thousands of years, wind-whipped, twisted bristlecone pines have been clinging to existence on the arid, stony crests of eastern California’s White Mountains, in conditions inhospitable to most other life.

Their growth rings provide a year-by-year account of the struggle to survive: It’s a tortuous cycle of dying off almost entirely, leaving only a few strips of bark that then continue to grow diagonally skyward or sideways along the ground.

But the world’s oldest trees may never have experienced temperature increases as rapid as those of recent decades. The climatic changes have triggered a struggle for dominance, in very slow motion, between the ancient bristlecones and the younger limber pines that have been able to charge up-slope as conditions become warmer and wetter. Will they cope with the intrusion of limber pines competing for sunlight, moisture, nutrients and room to grow?

Bristlecone pines — named for their bottlebrush-like branches with short needles — are found in other parts of the semiarid Great Basin, which extends from California’s Sierra Nevada east to the Rockies. But the ones found in the White Mountains are the oldest. The slow growers are only about 25 feet tall and expand about 1 inch in diameter every 100 years.

One of the oldest of the bunch is Methuselah, at about 4,768 years old. Its precise location is carefully guarded to avert vandalism.

According to Smithers, who led a study of ancient bristlecone pines published in the journal Global Change Biology, forests of limber pines have been steadily pushing up-slope over the past 50 years throughout the Great Basin.