Signs of Climate 'Doomsday' Clearly Visible in Leaves

Jakarta, CNBC Indonesia – The signs of damage to the Earth caused by climate change are becoming increasingly real. One sign of climate change ‘doomsday’ driven by global warming can even be seen in the condition of leaves in forests.

Global warming has begun to threaten the forest’s function as the lungs of the world. Yet trees play a vital role in absorbing carbon dioxide through photosynthesis and producing oxygen for the atmosphere.

If the condition of forests continues to deteriorate, the impact will not only damage the environment but could also make it difficult for humans to breathe.

Trees in forests are usually exposed to sunlight and absorb water through their roots. However, because the sun has become too intense, temperatures have grown excessively hot, potentially halting the process of photosynthesis.

Research by Gregory Goldsmith of Chapman University in California and his team found that some parts of tropical forests are approaching the temperature limit, disrupting photosynthesis.

“The study shows that leaves in tropical forests, in certain places and at certain times, have already exceeded the critical temperature threshold,” said Goldsmith.

Trees in tropical forests can carry out photosynthesis at temperatures of up to 46.7 degrees Celsius. However, the researchers explained that this ability differs between species, depending on the forest population, the number of leaves on a tree, and the canopy.

For this reason, the team from Northern Arizona University used data from NASA’s ECOSTRESS sensors, which measure the Earth’s surface temperature, to identify leaves in tropical forests that have become too hot to photosynthesise.

The data collected from satellite monitoring during the 2018–2020 period was then validated with on-the-ground sensors placed in the treetops of five forests in Brazil, Puerto Rico, Panama and Australia.

The analysis found that forest canopy temperatures peaked at 34 degrees Celsius during the dry season, although some leaves reached 40 degrees Celsius. A small fraction of leaves — 0.01 per cent of the sample — exceeded the critical temperature of 46.7 degrees Celsius at least once during the dry season.

“Although still rare, extreme temperatures can have a disastrous impact on leaf physiology. It can be classified as a low-probability event with extraordinary consequences,” the research report stated.

According to ScienceAlert, trees close the pores on their leaves, called stomata, to conserve water whenever temperatures become too hot.

This closure of the stomata means the leaves are at risk of damage because they cannot ‘cool themselves’ through the process of transpiration. During dry periods, when the soil hardens, the impact of heat stress can become even more severe.

“Believe it or not, we don’t know much about why trees die,” said Goldsmith. Scientific understanding of the effects of heat and drought, water and temperature, on plants remains very limited.

The research team then used their data to run simulations to understand how tropical forests respond to rising temperatures and increasingly frequent droughts.

The simulations showed that 1.4 per cent of forest canopy tops could stop photosynthesising in the near future as a consequence of global warming.

If global warming exceeds 3.9 degrees Celsius, entire forests could become unable to cope. Leaves would dry out and trees across the forest would die one by one.

However, the researchers stressed that these calculations represent probabilities only. Severe impacts could well occur at different temperatures. For this reason, curbing emissions and preventing deforestation are essential to protect tropical forests.