ISTANBUL 

Australian tropical forests have shifted from being carbon sinks – which can absorb the planet’s harmful excess carbon – to carbon sources, according to a study published Wednesday in science journal Nature.

A long-term declining trend in the carbon sink capacity of woody aboveground biomass in Australian moist tropical rainforests has been detected, according to the study, titled Aboveground biomass in Australian tropical forests now a net carbon source.

"Woody biomass switched from being a carbon sink to a carbon source around the year 2000, notwithstanding some lag in realized emissions due to decomposition of tree necromass," it added.

The data indicate that the transition took place around 1998, while a simple linear model places the change closer to 2000.

Tropical forests serve as major global carbon sinks – natural systems that absorb carbon dioxide from the atmosphere. Earth system models predict that these forests will continue to increase their carbon sink capacity in the near term, as higher atmospheric carbon dioxide levels are expected to stimulate tree growth.

However, the study’s findings suggest that woody aboveground biomass in moist tropical forests worldwide could respond to climate change in a similar way to Australia’s, potentially leading to a long-term shift from carbon sinks to carbon sources.

Although moist tropical forests of Australia are relatively small in extent, they are among the highest-biomass tropical forests of the world. Changes in them may demonstrate the future climate change response of more extensive forests in the Amazon, Africa, and Asia and may also indicate the consequences of increasing cyclone frequencies for tropical forests in the Philippines, Central Asia, Madagascar, and Central America, it said.

Rising CO2 levels in Earth’s atmosphere fuel global warming and are one of the most dire threats to the continued existence of human life on Earth.