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Global heating has caused ‘shocking’ changes in forests across the Americas, studies find | Climate crisis

Forests from the Arctic to the Amazon are transforming at a “shocking” pace as a result of the climate crisis, with trees encroaching on the previously barren tundra in the north, while dying from increasing heat further south, scientists have found.

Global warming, along with changes in soil, wind and available nutrients, is rapidly changing the composition of forests, making them much less resilient and more susceptible to disease, according to a series of studies examining the health of trees in the North and South. America have analyzed .

Many forest areas are now becoming more susceptible to severe wildfires, releasing even more greenhouse gases from these vast carbon stocks that are heating the planet even more. “It’s like people lit a match and now we’re seeing the result,” said Roman Dial, a biologist at Alaska Pacific University.

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Dial and his colleagues have found that a patch of white spruce in northwestern Alaska has “jumped” north into an area of ​​the Arctic tundra where there have been no such trees in thousands of years. The scientists’ new research report, published in Nature, estimates that the spruce trees are moving north at a rate of about 2.5 miles (4 km) per decade, aided by rising temperatures and changes in snow and wind patterns influenced by marine contraction. ice in the region.

“It was shocking to see trees there. Nobody knew about them, but they were young and growing fast,” said Dial, who first saw the shadows of the trees on satellite images and then took a single-engine plane trip, followed by a five-day hike, to search and study the encroaching forest. .

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“The trees actually jumped over the mountains into the tundra. Judging by climate models, this wouldn’t happen for a hundred years or more. And yet it is happening now.”

The Arctic is warming several times faster than the global average, and the emergence of dark conifers on previously pristine white tundra threatens to absorb more sunlight rather than reflect it, causing further warming. The trees can also disrupt the migration of several local species. “These trees move very quickly,” Dial said.

Further south, separate research has shown that a transformation is underway at the boundary between the boreal and temperate forests, with spruce and spruce species becoming less resilient to the warmer conditions. Scientists estimate that even small amounts of further heating, caused by human activity, can kill up to 50% of traditional boreal forest trees in places, stunting many other trees.

“Boreal species are doing very poorly, even with modest warming. They grow more slowly and have a higher mortality rate,” said Peter Reich, a researcher at the University of Minnesota who co-authored the study. “Intuitively, I thought they would do a little worse with 1.5°C warming, but they’re doing much worse, which is worrying.”

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Reich and his colleagues spent five years growing nine different tree species from seedlings under different conditions in northern Minnesota, exposing them to varying amounts of heat and water. The boreal species were found to have suffered as the soil dried out from the heat, while other more temperate species, such as oak and maple, coped better and may be able to slowly shift into the boreal zone as the world warms further.

“Given how fast climate change is, we could have a 50 to 150 year period where spruce and spruce over thousands of miles, including from Siberia to Scandinavia, don’t regenerate, so you get this strange new system of invasive shrubs that won’t let us down.” provide the economic and environmental services we are used to,” Reich said.

The impact of the climate crisis is also being felt in the heart of the Amazon, a closer study has highlighted. Scientists have expressed concern that the vast rainforest ecosystem is in danger of falling into a new, altered state and eventually turning into a savanna, and the new research found that a lack of phosphorus in the Amazon’s soil could have “major implications.” for its resilience to global warming.

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