A study published in the journal Nature has shown that tropical forests could become so hot that some kinds of leaves will no longer be able to conduct photosynthesis.
The research which suggests that forests may be nearing dangerous temperature thresholds sooner than expected, showed that the photosynthetic machinery in tropical trees begins to fail at about 46.7C on average.
Using a combination of high-resolution data from Nasa’s thermal imaging instruments on the International Space Station and ground-based experiments in tropical forests across the world, the researchers found that a small fraction, approximately 0.01% of all leaves, are already exposed to temperatures beyond their functional limits.
In his reaction, Chris Doughty, an associate professor of ecoinformatics at Northern Arizona University who also lead researcher of the study said that warming leaves, even if now in low numbers, act as a “canary in a coalmine for tropical ecosystems,”.
He said that the leaf-warming experiments had revealed a nonlinear rise in temperatures. “We were really surprised that when we warmed leaves by 2, 3 or 4C, the highest leaf temperatures actually increased by 8C. This shows a concerning nonlinear feedback that we were not expecting,” said Doughty.
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He added that “If we adopt a do-nothing response to climate change and tropical forest air temperatures increase by greater than 4C, there could be massive leaf death, possible tree mortality and species turnover across all tropical forests,”.
Mat Disney, a professor of remote sensing at University College London, said that In terms of global impact, “the photosynthetic response would be the tip of the iceberg in terms of effects – reduced carbon uptake, likely increased mortality and even triggering possible transitions from forest to savannah,”.
Report shows that at least 50% of global CO2 exchange occurs through forest canopies, which act as key regulators of our climate.
“The importance of this work is that it is a first look at the specific impact of this leaf-scale warming on photosynthesis in tropical forests,” Disney said. “So while it is quite specific in one sense, it also provides a really interesting look at one of the underpinning processes in this region, and what might happen to it in the near future if we don’t act fast.”
Simon Lewis, a professor of global change science at University College London, said that avoiding high emissions in the first place was key to stabilising temperatures.
“We should do all we can to avoid high-emissions scenarios. Under low-emissions scenarios, almost all tropical forest tree leaves can avoid death from overheating and the trees will survive,”.
Story was adapted from the Guardian.
