Critical Temperature Rise Reduces Tropical Tree Lifespan

For the first time, researchers provided clear evidence that there is a reduction in the lifespan of a tropical tree above a life-threatening temperature threshold.

The study findings recently published in the Proceedings of the National Academy of Sciences or PNAS journal present that lifespans of trees decline for temperatures higher than 25 degrees Celsius across the tropics.

As temperatures rise quickly across the tropics' large areas, trees' mortality is likely to quicken in significant parts of the tropics, including the Atlantic, Pantanal, and Amazon forests, with effects on air quality, animal habitats, and carbo stocks.

Even though tropical rainforests account for just seven percent of the land, they are considered home to roughly 50 percent of all animal and plant species and about 50 percent of forest carbon stocks on this planet.

(Photo: Richard Heathcote/Getty Images)
Recent study findings showed that lifespans of trees decline for temperatures higher than 25 degrees Celsius across the tropics.

'Temperature Threshold'

Consequently, minor changes in the tropical forests' functioning can substantially change the atmospheric levels of CO2, the essential anthropogenic greenhouse gas.

This new study's co-authors are Leeds' School of Geography's Professor Manuel Gloor and Dr. Roel Brienen. According to Gloor, "Many regions in the tropics are heating up" particularly fast, and significant areas are likely to become warmer, on average, than about 25 degrees Celsius.

Their findings, he added, which are the first to present a temperature threshold, proposes that for trees found in these regions, their lifespan is possible to be adversely impacted.

Besides, Brienen explained that the results specify that "tropical forests may be more vulnerable" to the heat's rise than previously perceived.

As a result of global warming, the study authors said they are expecting shortened tree lifespans in the tropics.

These results, they said, are warning indications that, together with deforestation, global warming is adding extra stress to Earth's tropical forests.

4 Years of Study

The team of researchers, which Dr. Giuliano Locosseli from the Institute of Biosciences, University of Sao Pulo Brazil, led, spent four years investigating what's described as "tree-ring data" over 100,000 trees globally, belonging to 400 different tree species from 3,000 locations across the world.

Science Bulletin reported, according to Locosselli, in the tropics, trees are growing, on average, double as fast as those found in cooler places of the world.

However, they have a shorter lifespan and, on average, of 186 years, compared to trees in other climates with a lifespan of 322 years.

In their analysis, the researchers propose that the lifespans in the tropics will possibly decline further still. If tropical trees die earlier, the study investigators said, it will impact "how much carbon these forests can hold," drawing apprehensions about the forests' future potential to offset emissions of CO2 from fossil fuel burning. It could lead to changes in biodiversity and a drop in the number of species on Earth.

At present, average temperatures in tropical forests vary from 21 degrees Celsius and 30 degrees Celsius. Based on the most recent forest forecasts, "tropical temperatures on land will continue to rise," approaching a combined 2.5 degrees Celsius averagely above pre-industrial levels over the next decade or two.

The study presented that dry conditions will further worsen temperature impact on the tree's longevity. Climate change, it also specified, will affect the tropical rainforests outside of South America, like west Africa's Congo Forest, the world's second-largest tropical forest next to Amazon.

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