SYDNEY, Oct 16 (NNN-AAP) – Australia’s tropical rainforests have become a net source of carbon dioxide to the atmosphere, driven largely by rising temperatures, air dryness and droughts, linked to human-driven climate change, new research shows.
The study published in Nature has found that Australia’s wet tropics are the first of their kind globally, to show this response to climate change, according to a statement released today by Australia’s Western Sydney University (WSU).
“Forests help to curb the worst effects of climate change by absorbing some of the carbon dioxide released from burning fossil fuels, but our work shows this is under threat,” said study lead author, Hannah Carle from WSU’s Hawkesbury Institute for the Environment, part of an international team, including researchers from the Australian National University.
Tropical forests, among the most carbon-rich ecosystems on the planet, can be expected to absorb more carbon than they release, which is known as a carbon sink, Carle said.
However, the new study has found that, the capacity of woody biomass, tree trunks and branches in Australia’s tropical rainforests, to continue working as a carbon sink is at risk.
The change is largely due to increased tree mortality driven by climate change, including increasingly extreme temperatures, atmospheric dryness and droughts, Carle said.
“Regrettably, the associated increase in carbon losses to the atmosphere has not been offset by increased tree growth. This is surprising because higher carbon dioxide levels should make it easier for plants to scavenge carbon dioxide from the air, leading to more tree growth and greater carbon sink capacity,” Carle said.
The findings have significant implications for emissions reduction targets, which are partly based on the estimated capacity of ecosystems to continue to absorb emissions and help mitigate climate change.
“Current models may overestimate the capacity of tropical forests to help offset fossil fuel emissions,” said Carle, adding that, the study also points to cyclones, which suppress the carbon sink capacity of woody biomass in these forests, become increasingly severe under climate change, and to impact areas further southwards.
Researchers note the need to monitor whether similar shifts will occur in other tropical forests globally, a topic that needs further research.– NNN-AAP
