If this trend continues, it could spell disaster for Earth’s climate systems and biodiversity. The findings have been published in the journal Nature. From the report: The average critical temperature beyond which photosynthetic machinery in tropical trees begins to fail is 116 degrees Fahrenheit (46.7 degrees Celsius). Currently, only 0.01 % of all leaves surpass this critical temperature every year. But scientists warn that air temperature rises of 7.2 F (4 C) could push trees in tropical forests beyond a tipping point and into mass death. “It’s concerning from our perspective that you see nonlinear trends. So you heat the air by, let’s say, 2, 3 degrees Celsius [3.6 to 5.4 F], and the actual upper temperature of these leaves goes up by 8 degrees [Celsius; 14.4 F],” Christopher Doughty, an associate professor of ecoinformatics at Northern Arizona University, said during a press conference on Monday (Aug. 21). “Even though a small percentage of leaves are currently doing this, our best guess is that a 4 degrees Celsius increase in temperature could cause some serious issues for certain tropical forests.” […]
Plugging these peak temperatures into a mathematical model, the scientists found that an average 7 F (3.9 C) increase in the air temperature surrounding the leaves caused those most exposed to the heat to have their water-carrying stomata closed off by the tree, leading to their deaths. This triggered a cascade effect, increasing the temperature around the remaining leaves and potentially killing them, their branches and the trees in turn. “If you have 10% of the leaves dying, the whole branch is going to be warmer because a critical part of that branch can no longer cool the broader branch. Likewise you can make that assumption across the whole forest when a tree dies,” Doughty said.
