A tower bristling with sensors juts above the canopy in the northern Democratic Republic of Congo, measuring carbon dioxide emitted from the world's second-largest tropical rainforest. 

Spanning several countries in central Africa, the Congo Basin rainforest covers an immense area and is home to a dizzying array of species. 

But there are growing concerns for the future of the forest, deemed critical for sequestering CO2, as loggers and farmers push ever deeper inside.

Scientists at the Yangambi Biosphere Reserve in the DRC's Tshopo province are studying the rainforest's role in climate change — a subject that received scant attention until recently.

Standing 55 meters tall, the CO2-measuring flux tower came online in 2020 in the lush reserve of 250,000 hectares (620,000 acres).

Yangambi was renowned for tropical agronomy research during the Belgian colonial era. 

This week, it also hosted scientists as part of meetings in the DRC dubbed pre-COP 27, ahead of the COP27 climate summit in Egypt in November.

Thomas Sibret, who runs the CongoFlux CO2 measuring project, said that flux towers are common worldwide.

But until one was set up in Yangambi, there had been none in Congo, which had "limited our understanding of this ecosystem", he said.

Around 30 billion tonnes of carbon are stored across the Congo Basin, researchers estimated in a study in Nature in 2016. The figure is roughly equivalent to three years of global emissions.

Sibret said more time is required to draw definitive conclusions from the data gathered by DRC's flux tower, but one thing is certain: The rainforest sequesters more greenhouse gases than it emits.