Rising seas threatenSouth Africa's coastlines, battering cities with floods and erosion. Yet in a surprising twist of climate science, the ground beneath parts of the country seems to be rising.

Researchers from Germany believe drought and resulting water loss due to global warming may be causing parts of South Africa to lift out of the ocean by two millimeters each year. 

South Africa's coastal cities like Cape Town, Durban, and Port Elizabeth experience eroding shorelines,frequent flooding, and the loss of critical infrastructure and natural habitats.

The country also experienced a series of extreme weather events in 2017: massive waves, storm surges, heavy rainfall, wildfires, and hurricane-force winds that devastated the southwestern cape. 

The storms resulted in at least eight deaths and damaged 135 schools. Approximately 800 homes in Cape Town were flooded. 

Such incidents underscore the growing risks to South Africa's coastal regions posed by increasing weather hazards, which scientists predict will be more frequent and intense due to rising global temperatures. 

David Willima, an ocean governance policy researcher in South Africa, said integrating climate and ocean concerns at the policy level was important to effectively address the rising sea level threat.

"The problem has been that South Africa hasn't successfully linked climate and ocean discussions, they're often treated as separate issues," Willima said. 

Climate change is lifting the continent up

Just as threats of rising seas grow, scientists have observed that parts of South Africa's coastal regions are gradually lifting.

Changes in land elevation have usually been attributed to deep earth processes such as the movement of hot materials beneath the crust. 

However, a recentstudyled by Makan Karegar, a geodesist at the University of Bonn, challenges that view.

The research points to droughts as the primary driver. 

"Groundwater adds weight to the land," Karegar told DW. "A lot of rain and flood put weight on the Earth's crust, surface and that weight causes [it] to go down." 

During drought, as water is lost from the soil and underground reservoirs, the land becomes lighter and can rise up, similar to the way a sponge expands when it dries.

The researchers used GPS measurements, satellite data, and hydrological models to study the correlation between areas experiencing severe droughts and significant land uplift.

Jasper Knight, a geoscientist at the University of Witwatersrand in Johannesburg, who was not involved in the study, considers the research scientifically sound. 

"They used high-quality data and strong modeling techniques and the ways in which they are applying it for southern Africa is of interest," Knight said. 

"They suggest that climate variability is an important determinant of systematic variations in land surface elevation across the region compared to a kind of traditional idea, based upon a tectonic uplift of the land surface."

A silver lining or not?

While the phenomenon may appear to offer a natural buffer against rising sea levels, Knight cautions against drawing overly optimistic conclusions.

"Of course, you may say if the land surface is rising, then in a relative sense the sea level may be static or may be going down," Knight said.

"But of course, that may be at the expense of less water being present on the land surface. And here if I had to decide between a decreasing sea level rise at the coast versus drought in the interior, I would choose sea level as the least-worst option."

Karegar adds that while some countries artificially raise land elevations by injecting wastewater underground to reduce flooding risk, South Africa's situation is a byproduct of natural drought. 

Still, he said the insights from the study could aid broader environmental management.

"These findings could help improve drought and flood monitoring, guide groundwater management, and inform more strategic water resource planning and climate adaptation efforts," he said.

Edited by: Matthew Ward Agius

Sources

GNSS Observations of the Land Uplift in South Africa: Implications for Water Mass Loss