A 20-year study conducted in the primary tropical seasonal rainforest of Xishuangbanna, Southwest China, has confirmed its role as a robust and strengthening carbon sink. The research, based on continuous atmospheric measurements, highlighted the critical role of well-protected primary forests in mitigating climate change.

Published in Agricultural and Forest Meteorology, the study analyzed data from 2003 to 2022 using the eddy covariance technique to measure the exchange of carbon dioxide (CO₂) between the forest and the atmosphere.  The results demonstrated that this protected rainforest can strengthen carbon sink.

The analysis showed that the forest consistently absorbed more CO₂ than it released. This carbon sink strengthened significantly over time at a rate of 3.4% per year. Contrary to expectations, the rainforest exhibited a stronger carbon sink during the six-month dry season, which contributed a remarkable 93.9% of the annual total carbon absorption. Increased solar radiation and precipitation during the dry season over the 20 years were key drivers boosting this seasonal sink.

While the long-term trend is upward, the annual carbon sink temporarily declined for approximately two years following severe drought events (e.g., in 2009 and 2014), underscoring the ecosystem's sensitivity to extreme weather. The forest's carbon use efficiency (how well it converts absorbed carbon into biomass) also showed a positive trend, increasing by 2.4% per year. This indicates a growing capacity for carbon storage within the living plants and soil.

"Our research underscores the vital importance of preserving primary tropical forests. Xishuangbanna rainforest is not just a stable carbon sink, it's an increasingly efficient one. This highlights its invaluable role in the global carbon cycle and for future climate predictions," said SONG Qinghai of XTBG.

Available online:  21 September 2025