Researchers believe that nutrient limitations, especially a lack of phosphorus, could be preventing this expected growth response. The world’s tropical forests are in crisis, highlighted by a worrying change in Australia’s tropical forests. Researchers in Nature say these ecosystems are now releasing more carbon than they absorb. This shift serves as a serious warning for all tropical forests worldwide, just as international leaders prepare for the 30th annual United Nations Climate Change Conference, or COP30, in Belém, Brazil, starting November 10.
A long-term study from 1971 to 2019 showed that the woody biomass, which includes the structure of branches and trunks, in Australia’s rainforests has been shrinking since around 2000. Ecophysiologist Hannah Carle and her colleagues from Western Sydney University pointed to an increase in tree deaths as the cause of this decline. Human-caused climate change directly links to this rise in mortality. Rising temperatures, prolonged droughts, and destructive tropical storms are among the factors contributing to this decline. When trees die, the carbon that was stored in their wood goes back into the air.
The research team believes that nutrient limitations, especially a lack of phosphorus, could be preventing this expected growth response. Surprisingly, the study also found that the rising levels of carbon dioxide in the atmosphere, which climate models once predicted could help plant growth and reduce forest loss, did not lead to significant improvements in growth. It can be mentioned that researchers are hopeful that COP30 will focus on the fragile state of tropical forests around the world, particularly the vast Amazon rainforest. Covering an area nearly as large as the continental United States, the Amazon currently absorbs a quarter of the carbon dioxide taken in by land-based ecosystems annually. Forest ecologist Wannes Hubau from Ghent University described this situation as alarming, highlighting that even healthy African tropical forests—those undisturbed by fragmentation or thinning—started showing increased tree mortality around 2010. Hubau noted, “African tropical forests seem to be the last man standing.”
At the COP26 summit in Glasgow four years ago, nearly 140 nations pledged to stop and reverse the loss of all forests and land degradation by 2030. However, a recent report from the U.N. Environment Programme (UNEP) reveals that the world is significantly behind in achieving this goal. Moreover, the world currently considers about 291 million of its 1.6 billion hectares of tropical forest at high risk of loss. These forests are crucial for human well-being, providing services like food security, rainfall recycling, pollution filtration, and protection from natural disasters. It can be depicted that these funds are essential for supporting sustainable agriculture, creating supply chains that do not drive deforestation, and improving regulation and enforcement.
Hubau emphasizes the need for increased protection for all tropical forests, even those that have lost their effectiveness as carbon sinks. He pointed out that they are significant reservoirs of carbon, and their declining ability to store it means that the carbon saved over centuries must be fiercely protected. Otherwise, failing to protect them will release a surge of additional CO₂ into the atmosphere, further worsening the climate crisis.
