At dawn on 19 October, residents along Ghana’s Keta Lagoon found a chalk-white sheen across shallow water that had appeared dark the evening before. Scientists say the “white tide” was a salt crust left as unusually saline water evaporated — and that measurements taken around it point to a troubling shift in the lagoon’s mangroves.
A team from the fictional Gulf Estuary Research Centre says its eight-year field record shows a critical regeneration threshold has now been crossed across about 4,900 hectares (12,100 acres) of the delta. Seedlings are failing in areas where root-zone salinity has repeatedly exceeded 22 parts per thousand, the researchers said in a paper published on Monday.
A coast turning saltier
The pale crust itself is not evidence of a tipping point, said Dawid Sikorska, an ecologist who led the research. The finding rests on 186 water and soil samples, monthly seedling counts and records from 14 monitoring plots. In the most affected plots, young mangroves have not replaced mature trees for three successive growing seasons.
“We are seeing the system stop repairing itself,” Sikorska said. If dry seasons lengthen and freshwater inflow continues to fall, the team’s worst-case model projects 2,700 hectares (6,700 acres) lost by 2040. That could release up to 2.7 million tonnes of carbon dioxide equivalent by 2050, the researchers estimate; they caution that the figure depends on how quickly dead roots and soils decompose.
“This is the moment we can still turn a threshold into a recovery plan.” — Dawid Sikorska, ecologist
Salt producers seize authority
The science announcement landed as the Volta Estuary Salt Producers’ Council voted 42-6 on Sunday to strip the Keta Shore Management Board of its power to issue local salt-pan permits. The council says it will use the authority to halt new pans near restoration zones and direct part of its GH₵410 million (about €28 million) reserve towards mangrove planting and freshwater channels.
Goda Benius, the council’s chair, said members cheered when the vote was announced. “For years we were told the lagoon could take one more pan, one more dry season,” Benius said. The board called the vote legally invalid and warned that a permit freeze could threaten seasonal work and salt supplies.
Officials reject the tipping-point claim
The Ghana Climate and Coast Authority said the white film was a natural product of evaporation and that the research did not establish irreversible change. It urged residents not to abandon fishing grounds or salt work, while saying it would review a proposal for a controlled release of 45 million cubic metres of water from the lower Volta system before the next dry season.
Sikorska said the authority’s reassurance confused the visible salt crust with the longer record of seedling failure. A freshwater release could help, he said, but only if it arrives before the lagoon’s dry-season salinity peaks. The researchers have asked for a trial release by December and a six-month pause on permits beside the monitoring plots.
The government has not committed to either measure. The shore board says its mandate remains in force, setting up a dispute over who can act as the lagoon enters its hottest months. For scientists and salt producers who have spent years arguing over what the changing water means, Monday brought a rare point of agreement: the warning is no longer theoretical.
