Thirty Billion Tonnes of Wet Ground
Under the flooded forest of northern Congo lies the largest tropical peatland complex on earth, and nobody had measured it until a team went in with a soil auger and started counting. What they found holds roughly three years of the world's fossil fuel emissions, and it stays where it is only for as long as it stays wet.
The Likouala has almost no roads in it, which is the first thing to understand about the place. You move by pirogue on the Likouala-aux-herbes and the Ubangi, between fishing camps and villages built on the few metres of firm bank, and everywhere else the forest stands in water. Step off the path and your boot goes in to the calf, then the knee, and what comes up is black, fibrous and smells of nothing much. It is not soil. It is dead plants that have been failing to rot for ten thousand years.
For most of the twentieth century that ground was on maps as swamp forest and nothing more. It turned out to be the largest tropical peatland complex in the world, sitting across the border between the Republic of the Congo and the Democratic Republic of the Congo, and the reason nobody knew is the reason it survives: it is extremely difficult to walk into and there is nothing on the surface to see.
What was under the swamp
The measuring was done the slow way. A team led from the University of Leeds, working with researchers from Marien Ngouabi University in Brazzaville and the Wildlife Conservation Society, spent field seasons pushing corers into the peat, recording how deep it went and how much carbon each core held, then matched what they found on the ground to satellite imagery so the pattern could be extended across country they had not walked. The results were published in Nature in January 2017. The complex covered about 145,500 square kilometres — larger than England — and held on the order of 30 billion tonnes of carbon, roughly the equivalent of three years of global fossil fuel emissions, in an area that is a fraction of one per cent of the earth's land surface. The deepest cores went down about six metres and the oldest peat had begun forming around ten thousand years ago. A second mapping effort published in 2022, with far more field cores including new ones from the Congolese side, revised the area upward to something nearer 167,600 square kilometres and left the carbon estimate in the same range. Roughly a third of it lies in the Republic of the Congo.
Wet is the whole instruction
Peat exists because decomposition needs oxygen and waterlogged ground has none. Leaves and roots fall into standing water, the bacteria that would ordinarily consume them cannot work, and the material accumulates a fraction of a millimetre at a time for millennia. That also describes exactly how the store is lost. Drain a peatland — dig a canal, cut a drainage ditch for a plantation, lower the water table with a road embankment — and air reaches the peat, the bacteria start work on ten thousand years of accumulated carbon at once, and the ground begins emitting. Dry peat also burns, downwards and invisibly, and is very hard to put out. Indonesia demonstrated all of this at scale: peatlands drained for oil palm and pulpwood, and the fire seasons that followed, most severely in 2015, put smoke across three countries and released carbon on a scale that showed up in the global figures. The lesson for the Congo basin is not the usual conservation instruction to keep people out of a forest. It is narrower and stranger: keep the water in.
The Congo peatlands do not need to be guarded so much as left undrained. A logging road built at the wrong height across the wrong swamp does more damage than every chainsaw that will ever use it.
The Brazzaville argument
Congo moved on the diplomacy faster than it moved on anything else. In March 2018 the country hosted a meeting of the Global Peatlands Initiative in Brazzaville at which it, the Democratic Republic of the Congo and Indonesia signed a declaration committing to protect the peatlands and to cooperate on managing them — the three states holding most of the world's tropical peat, agreeing in public to treat it as a category of its own. In October 2023 Brazzaville hosted again, this time the Three Basins Summit, bringing together the Amazon, the Congo and the forests of South-East Asia. The argument Congo makes at these events is consistent and it is not a plea. It is that the country is holding an asset the rest of the world has already spent its own version of, that keeping it intact has an opportunity cost measured in the industries it forgoes, and that the cost should be paid rather than assumed. Congo has signed with donor mechanisms such as the Central African Forest Initiative, which pays for verified reductions in deforestation, and the sums involved so far are small next to what a barrel of oil earns.
And the oil
That last point is where the position gets uncomfortable, and it is worth stating fairly rather than as a gotcha. The Republic of the Congo runs on hydrocarbons. Oil supplies the great majority of export earnings and most of what the state spends, the country joined OPEC in 2018, and the fields that pay for the schools are offshore of Pointe-Noire, a thousand kilometres from any peat. Across the river the tension is more direct: in July 2022 the Democratic Republic of the Congo opened an auction of 27 oil blocks and three gas blocks, several of which overlapped the peatland complex, and defended it in almost the same language its neighbour uses about forests — that a poor country is entitled to develop the resources under its own ground, and that nobody proposing otherwise has offered to cover the difference. Both governments are making a version of the same argument. One of them is making it about what should be left alone and the other about what should be dug up, and the mud in question is continuous under both.
Who lives on it
The peatlands are not empty and this is the part most easily lost in the carbon arithmetic. People fish the flooded forest, cut a little timber, hunt, and move by water because there is no other way to move. The Lac Télé Community Reserve, gazetted in 2001 and covering roughly 4,400 square kilometres of the Likouala, was set up on the premise that the villages inside it are the managers rather than the problem, and it sits over some of the deepest peat measured anywhere in the complex. Any scheme that pays Congo to keep the ground wet has to reach those villages, in cash they can use, on a schedule they can plan around — otherwise it is a transfer between capitals with a swamp attached to it, and the people standing in the swamp have no reason to care whether it works.
What makes this story unusual is how little needs to happen. Nobody has to plant anything, restore anything or reintroduce anything. The peat has been doing its work since before agriculture, and it will carry on doing it provided the water table is not lowered — which means the decisions that matter are dull ones about where a road is graded, whether a concession boundary follows the hydrology, and who signs off on a drainage plan. It is possible to lose thirty billion tonnes of carbon through a sequence of choices none of which looked like a decision about climate at the time. It is also possible not to, and that is cheaper. The difficulty is that doing nothing, correctly and for a very long time, is the one thing no institution is designed to be paid for.