Stumbling on submerged roots, attacked by bees and wading waist-deep through leech-infested water, the three researchers and their Pygmy guides progress at just 100 metres an hour through the largest and least-explored tropical bog in the world.

The group halt and unpack what looks like a spear, which is plunged over and over again into the waterlogged forest floor. Each time it brings up a metre-long core of rich, black peat made up of partly decomposed leaves and ancient plantlife. The deepest the steel blade reaches before meeting the underlying clay is 3.7 metres.

Leeds University forest ecologists Simon Lewis and Greta Dargie cheer. The peat bed below the tangle of trees and water in the geographical heart of Africa is much deeper than they expected; and because peat stores carbon and slows global warming, their new research conducted last week in the Democratic Republic of the Congo (DRC)will be welcome news for the 194 countries meeting in Bonn for the annual UN climate conference.

Lewis and Dargie surprised the world earlier this year when they showed that the peatlands on either side of the Congo river contained one third of all the world’s tropical peat and were five times more extensive than anyone had thought, stretching over 145,500 sq km (56,000 sq miles), an area larger than England.

Since 2012, the two researchers have spent months at a time wading through bogs and sleeping on makeshift platforms built above the crocodile-infested swamp forests in the Cuvette central region of the neighbouring Republic of the Congo. “We would see elephant feet and gorilla hands imprinted in the peat. We were increasingly in awe that a remote, almost unknown, wilderness such as this could still be found on Earth today,” said Lewis.

Working mainly in the dry season, they took more than 500 peat samples, and calculated that the central African peatlands hold 30.6 billion tonnes of carbon accumulated over 10,000 years – the equivalent to three years of the world’s fossil fuel emissions. This would make them one of the world’s most important carbon “sinks”, they said.

But their new exploratory research, conducted with the Congolese botanist Corneille Ewango, 50km from Mbandaka in DRC, suggests that central Africa’s inaccessible forest swamps could be even more important as a global carbon storehouse than they thought, and could need a global initiative to research and protect them.

Campaigners from Greenpeace and the local community of Lokolama are fighting to preserve the precious carbon stores. Photograph: Kevin McElvaney/Greenpeace

“While the extent of the peat is known, its depth is not. There is just no data. We are a long way from really knowing how much is there and need to do more research,” said Dargie.

“Maintaining these large stores of carbon must be a global priority. Only with strong scientific data on the peatland, and how it behaves or might react to future changes, can governments establish baselines and protections in international agreements to ensure it is preserved,” said Greenpeace forest campaigner Matt Daggett.

There is growing understanding that the fate of carbon sinks like the Congo basin peatlands will determine future climate change. If left alone, they are vital collectors of CO 2 ; but if the forests above them are felled and the land is converted to farming, as has been widely practised for the past 30 years in south-east Asia, then the dried-out peat emits vast quantities of CO 2 and intensifies climate change.

Tropical peatland stores around 2,000 tonnes of carbon per hectare but this has been barely recognised by governments which have continued to promote intensive farming on peatlands.

The draining of south-east Asia’s peat swamps and the felling of its trees has been a climate disaster, say scientists. Two months of intense peat fires started in August 2015 to clear land for palm oil and pulp and paper plantations in Indonesia released an estimated 884m tonnes of carbon dioxide, more than the European Union in its entirety emitted that year.

The Congo basin forest, the second largest in the world after the Amazon, has been relatively protected by its inaccessibility, but environmentalists say it is highly vulnerable and its peat could easily be destroyed. Pressure is building, they say, from logging companies and European governments to lift a 15-year-old moratorium on the allocation of new industrial logging concessions.

Logging on swamplands is prohibited in the DRC but, says the Rainforest Foundation UK (RFUK), Congolese legislation does not precisely define what constitutes a swamp. Its analysis suggests 3.4bn tonnes of carbon could be emitted if the concessions become active.

According to Greenpeace, nearly half of the DRC’s current logging concessions are in breach of the law because their permissions have run out and they do not have approved management plans. These concessions overlap around 10,000 sq km of peat swampland.

“If this forest is cut, there will be decomposition of the peat and vast quantities of CO 2 will be released into the atmosphere, said Dagett.

The Congolese government, which has welcomed the scientists, is cautious about further protection. “There must be a balance between the forests and development. It comes down to money,” said Joseph Katenga, forest adviser to Amy Ambatobe, the minister for the environment and sustainable development.

But communities living close to the carbon-rich swamps near Lokolama have welcomed the discovery of peat, hoping it would attract money to better protect their forests which they traditionally use for fishing and hunting.

“As indigenous people, peatlands are part of our heritage and their discovery for the world to see represents a great hope for future generations,” said Valentin Egobo, who speaks for the Lokolama community.

Researchers have been gathering data in the area since 2012. Photograph: Kevin McElvaney/Greenpeace

“We hope our government will support us in our role as guardians of this ancient forest and provide us with the needed support to safeguard peatlands for our children and for the world.

“We did not know the peat was there. This is very important for us but we also need development. Our schools are dilapidated. We are marginalised and impoverished,” Egobo added.

The future of the DRC rainforest may be determined next month when the Norwegian government is expected to decide whether to fund a French Development Agency plan to expand “sustainable” industrial logging in the region. This would allow local communities to benefit from their resources, according to the agency.

But Greenpeace, RFUK and a petition signed by 135,000 people in Norway and the UK have condemned the plan. “Norway risks putting globally significant stores of carbon at risk through misguided support for so-called sustainable forest management in DRC. Instead of expanding large-scale timber-felling, Norway should work with the Congolese government to shut down the half of the country’s logging areas which the law requires to be closed and returned to the state,”, said Simon Counsell, the director of the RFUK.

The need to protect the forests above the peatlands was emphasised last week by a major report showing that there is 40% more carbon stored in forested lands than in known fossil-fuel deposits worldwide.

“Releasing this carbon into the atmosphere through continuing deforestation not only commits us to the worst impacts of climate change, but also results in the loss of a globally important carbon sink.

“Protecting the carbon stored in forests is no different than taking action to ensure fossil deposits like coal stay underground,” said the report’s lead author, Martin Herold of Wageningen University in the Netherlands.