By Emily M. Smith – 9 October 2018 11:33:22Scientists are already working to save some of the world´s biggest trees.
From the mighty Himalayan balsam fir to the beautiful white cedar, some species are already being targeted.
But as climate change pushes forests farther north and warmer temperatures cause trees to grow taller and more heavily, it could be a tough road to climb.
The world has already seen a dramatic increase in tree mortality as global temperatures rise, according to an extensive new study published in Nature Climate Change.
But researchers found that the risk is increasing exponentially as temperatures rise further south, from the subtropical forests of Australia to the northernmost reaches of China.
And as they look to the Arctic, where global temperatures are projected to hit a record high, researchers are looking at the most vulnerable tree species.
These are species that are already vulnerable to warming because of the high mortality rates they can experience when they are found in extreme conditions.
“Climate change is already impacting the distribution of many species, and climate change will likely worsen the risk of climate-related mortality,” said senior author Andrew Ainsworth, a postdoctoral fellow in the Department of Biological Sciences at the University of Tasmania in Tasmania.
“It is vital that we understand the causes of the problem before it gets worse.”
What is the cause of the increased mortality rate of trees?
Ainsworth and his colleagues studied data from more than 20 years of tree mortality monitoring around the world, and found that warming conditions in the tropics is responsible for the vast majority of trees worldwide.
The tropics, which encompass the northern, central and southern hemispheres, is home to more than 60% of all tropical species and the majority of tree species found in the northern hemisphere.
But warming temperatures are also having a significant impact on the forests in the subtopics.
“A warming trend in tropical regions will have significant effects on tree species distributions in the north, which is likely to be one of the most important areas to address for future climate change mitigation,” Ainswicks said.
“Our results show that warmer temperatures are already impacting many of the tree species we know about and could be causing more species to become more vulnerable in the future.”
The tropics are home to a wide range of trees, ranging from white cedars to balsams fir.
Ainswell’s team found that climate change is affecting many of these species, with the white cede in particular suffering the most from rising temperatures.
“It’s likely that warmer temperature in the south will lead to greater mortality of the white-cedar, as this species is already threatened by drought, pests and competition from other species,” he said.
“This is particularly true for the balsamus fir, which also grows in the southern hemisphere.”
The authors believe that increased tree mortality will affect the health of species in the tropical regions as they compete with other species for the same habitat.
“There are a lot of species that have been impacted by climate change and now the impacts are spreading to other areas,” said Ainswick.
“There are some species that could be lost to the tropic if we don’t act now.”
What do the scientists think is causing the increased risk of tree loss?
A study published last year by researchers from the University, the University’s College of Agricultural and Environmental Sciences (CAESES) and the University´s School of Forestry and Environmental Studies (ESES), looked at how the tropically-vegetated tropical forests of the northern and southern halves of Australia had responded to climate change.
They found that tropical forests in Australia were already under pressure from climate warming and predicted further warming would push trees further south and into the polar regions, where they are at greater risk.
“When we look at the global tree mortality picture, we know that most species have already been affected by climate-induced mortality in their forests, with some species such as white cedes already suffering mortality rates up to five times higher than the average,” Alesworth said.”[But] there are still a number of tree-living species that we don´t yet know about.”
The researchers compared the risk for species living in the forests of both the tropical and temperate regions.
Trees in the temperate areas of Australia are already at risk from climate-driven mortality, and Ainswaits team found a clear correlation between tropical mortality and climate-linked warming in temperate forests.
“We found that when tropical regions were warming, mortality rates increased significantly, but the increase was not as large in temperated regions,” he explained.
“For example, the rate of mortality increased in the Southern Highlands of Australia from about 0.6 to 3.1 percent in just a few decades.”
Ainswoks team is working to determine what the exact cause of this rise in mortality is.
They believe the warming trend could be contributing to the higher mortality rates that have recently been seen in the polar region, but
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