Critical temperature for tropical tree lifespan revealed

Dead tree trunk in the rainforest of Peru. Credit: Roel Brienen

Scientists have provided clear evidence for the first time that the lifespan of tropical trees decreases above a critical temperature threshold.

Findings, published today in the journal PNAS (Proceedings of the National Academy of Sciences) show that in the tropics the lifespan of trees decreases at temperatures above 25 ° C.

As temperatures rise rapidly in many parts of the tropics, tree mortality is likely to increase in substantial parts of the tropics, including the Amazon, Pantanal and Atlantic forests, affecting animal habitats, air quality and carbon stocks.

Although tropical rainforests make up only 7% of all land, they are home to about 50% of all animal and plant species and about 50% of the carbon stock in Earth’s forests. Thus, small changes in tropical forest functioning can significantly alter atmospheric levels of CO2—The main anthropogenic greenhouse gas.

Professor Manuel Gloor and Dr. Roel Brienen, from the School of Geography in Leeds, are co-authors of the new study.

Professor Gloor said: “Many regions in the tropics are warming very quickly and large areas will on average become warmer than about 25 ° C.

“Our findings – which are the first to show that there is a temperature threshold – suggest that trees in these regions are likely to have a negative impact on their lifespans.”

Dr. Brienen added: “This indicates that tropical forests may be more vulnerable to increasing heat than previously thought. As a result of global warming, we therefore expect a reduction in the lifespan of trees in the tropics.

Critical temperature for tropical tree lifespan revealed

Tropical rainforest in Peru. Credit: Roel Brienen

“These results are a warning that, in addition to deforestation, global warming is adding stress to the world’s tropical forests.”

The research team, led by Dr. Giuliano Locosselli, of the Institute of Life Sciences, University of São Paulo, Brazil, spent four years examining tree ring data from more than 100,000 trees worldwide belonging to 400 different tree species from 3,000 locations around the world. .

Dr. Locosselli said, “In the tropics, trees grow on average twice as fast as in cooler regions of the world. But they also have a shorter average lifespan of 186 years, compared to 322 years of trees in other climates. Our analysis suggests that the lifespan in the tropics will likely decline even further.

“If tropical trees die earlier, it will affect the amount of carbon these forests can hold, raising concerns about the future potential of forests to offset CO.2 emissions from fossil fuel combustion. It can also lead to changes in biodiversity and a decrease in the number of species on the planet. “

Currently, mean temperatures in tropical rainforests range between 21 ° C and 30 ° C. Latest forecasts show tropical temperatures on land will continue to rise, reaching an average of 2.5 ° C above pre-industrial levels over the next 10 to 20 year. The study also shows that temperature effects on tree life will be further exacerbated by dry conditions.

Climate change will also affect tropical rainforests outside of South America, such as the Congo Forest in West Africa – the world’s second largest tropical forest after the Amazon.

Dr. Locosselli added, “While tropical rainforests in the Amazon are already close to this temperature threshold, temperatures in the Congo are lower. But with this large increase in temperature, we may start to see signs of increased tree dieback. Believe, the scenario is rather bleak.”

Professor Marcos Buckeridge, Director of the Biosciences Institute at the University of São Paulo, who is also a co-author of the study, added: “Temperatures will continue to rise for the foreseeable future, even if we take drastic measures to reduce emissions. to decrease.

“So it is inevitable that the critical threshold for tree life in the tropics will continue to be exceeded and it is therefore even more important to protect tropical forests and reduce greenhouse gas emissions.”

“Global Tree Ring Analysis Reveals a Rapid Decline in Tropical Tree Lifespan with Temperature” is published in PNAS (Proceedings of the National Academy of Sciences).


The decline in the lifespan of trees in forests could offset some of the increase in net carbon uptake


More information:
Giuliano Maselli Locosselli el al., “Worldwide Tree Ring Analysis Reveals Rapid Decline in Tropical Tree Life with Temperature,” PNAS (2020). www.pnas.org/cgi/doi/10.1073/pnas.2003873117

Provided by University of Leeds

Quote: Critical Temperature for Tropical Tree Lifespan Revealed (2020, December 14) Retrieved December 15, 2020 from https://phys.org/news/2020-12-critical-temperature-tropical-tree-lifespan.html

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