Climate change could kill world's oldest trees: study

Climate change could kill world's oldest trees: study
Warming temperatures due to climate change may spell the end for some of the oldest trees on the planet, a new study has warned.

Bristlecone pines - including Methusaleh, one of the world's oldest trees have lived in North America's Great Basin for thousands of years.

However, warming temperatures due to climate change could cause trouble for the ancient trees by tipping the ecological balance in favour of the conifer's neighbour, the limber pine, scientists said.

Both limber and bristlecone pines are adapted to the temperature and moisture of subalpine forests. As the species' favourite temperatures move up mountains due to climate change, logic says the trees should follow them upward.

Now a new study has found limber pines are leap-frogging over bristlecones: most of all the juvenile trees above the historic treeline are limber pines.

"The (trees) are not just moving in lock step. Species are moving around the landscape in unpredictable ways," said Brian Smithers, an ecologist at the University of California Davis.

As limber pines pile up above the historic treeline, it is possible they will use up so much light and water that it becomes impossible for bristlecone pines to join them, according to the researchers.

This could mean the end of ancient trees like 4,848-year-old Methuselah. While still uncertain whether the limber pine will completely win out over bristlecones, Smithers thinks we may see the loss of this iconic tree.

"I think what is going to happen - at least in some areas - is that we are going to lose bristlecone. There's not very much room upslope before you get to the top of the mountain," he said.

Below the treeline - altitude above which it is too cold for trees to grow - bristlecone is king. The tree dominates the subalpine community, growing in all spaces except in sandy, granitic soils, where limber pines huddle together.

As temperatures have steadily warmed with climate change, the vertical limit where trees can survive has creeped uphill.

Scientists estimated the historic treeline, based on where adult trees, above three meters tall, clumped together.

Above this line, they counted juvenile trees that had hopped over, identifying them and estimating their age based on scars on their stems.

They compared the community of young trees above the line to adult trees below the line to see how the species distribution changed.

"What we were finding is that limber pine is taking over the status of the treeline tree," Smithers said.

Above the treeline, young limber pines dominated, even encroaching on limestone and dolomite-based soils - normally the territory of bristlecones.

The limber pines spread faster than bristlecones, thanks to the help of the Clark's nutcracker, a bird that eats and disperses their seeds, Smithers said.

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