Tropical forests for a long time have absorbed billions of metric tons of carbon dioxide each year. That has helped to reduce the negative effects of climate change.
Now, tropical forests in Australia are causing worrisome concerns. Their capacity to absorb carbon dioxide, called carbon sink, may be in decline. This could indicate a possible future switch in which trees put out more carbon dioxide than they absorb from the atmosphere.
Because the Australian continent has one of the most variable climates on Earth and because it has a diverse range of different types of forests, the Australian tropical forests provide important information about trees all over the world.
Some of the worrisome concerns come from the increased mortality rate of trees due to climate-driven changes. Nature, a British weekly international scientific journal of peer-reviewed research, addressed the issue in its January 6, 2026 edition called "Pervasive increase in tree mortality across the Australian continent."
The publication compiled information collected during 83 years, 1941-2023, from about 2,700 forest plots across Australia. The forest plots included tropical savanna, rainforest, and warm and cool temperate forests. The collected figures explored patterns of tree mortality from a variety of causes. An abstract of the Nature article noted, "We found a consistent trend of increased tree mortality across the four forest biomes."
The findings suggest that ongoing climate change has pushed forest dynamics beyond their natural ability to recover. Increasing temperatures over time make it harder for trees to survive. As a result, they become less effective as absorbers of carbon dioxide. Higher mortality rates occurred among trees with low wood density, high specific leaf area and short maximum height.
Much more information needs to be gathered to help understand all the dynamics involved in the trend. Some climate models indicate that more carbon dioxide in the atmosphere could encourage more plant growth, according to a January 2026 article in Science News. But researchers did not find a significant increase in tree growth. It's possible that more nutrients are needed for that growth to occur. If so, limited nutrients need to be included in future climate models.
In any case, tropical forests need to be protected, and that could cost many billions of dollars. The United Nations Environment Program (UNEP) suggests the costs for such protections could reach $498 billion by 2050. UNEP is a leading global authority on the environment. The cost is steep, but not protecting the forests may make it harder for many species on Earth to survive.