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Cape Town, South Africa
The rising sea level is sinking the coast of South Africa, but drought is leading to underground water reduction, which is simultaneously raising some parts of the coastal region.
As seas go up along the back of South Africa, a natural opposite force is in action: drought. New investigations reveal that parts of the country are slowly move away from the ocean due to the loss of water in the underground.
The sea climb threatens the South African backs, plaguing cities with flooding and erosion. However, in a surprising turnaround of climate science, soil under parts of the country It seems to go up.
German researchers believe that drought and consequent loss of water due to global warming may be causing parts of South Africa move away from the ocean in two millimeters per year.
The coastal cities of South Africa, such as Cape, Durban and Port Elizabeth, suffer Erosion of the Coastal Linesfrequent floods and loss of critical infrastructure and natural habitats.
The country also recorded a Series of extreme meteorological phenomena In 2017: gigantic waves, storms, intense rains, forest fires and hurricane force winds that devastated the southwest of the cable.
Storms caused at least eight deaths and damaged 135 schools. About 800 houses in the city of Cape were flooded.
These incidents underline the increasing risks to coastal regions South Africa due to increased climatic risks, which scientists predict that they are more frequent and intense due to increased global temperatures.
David Willima, a researcher of the ocean governance policy in South Africa, said that the integration of climate and oceans at the political level is important to effectively address the threat of rising sea level.
“The problem is that South Africa has not been able to connect the discussions About climate and oceans, which are often dealt with as separate issues, ”said Willima.
Climate change are raising the continent
While the threats of rising seas grow, scientists have observed that parts of the coastal regions of South Africa They are gradually raising.
Changes in land elevation have usually been attributed to deep terrestrial processes, such as the movement of hot materials under the crust.
However, a study led by Makan Karegar, a geodesist from the University of Bona, challenges this vision.
The investigation points to dried as the main factor.
“The groundwater adds weight to the earth,” Karega told DW. “Lots of rain and floods put weight in the earth’s cruston the surface, and this weight causes it to go down. ”
During drought, as water is lost from soil and underground reservoirs, the earth becomes lighter and can riselike the way a sponge expands when it dries.
Researchers used GPS measurements, satellite data and hydrological models for Correlation between the areas affected by severe droughts and the significant elevation of the earth.
Jasper Knight, a geoscientist at the University of Witwatersrand, in Johannesburg, who was not involved in the study, considers the investigation scientifically solid.
“They used high quality data And solid modeling techniques and the way they are applying them to southern Africa is interesting, ”said Knight.
“They suggest that climate variability is an important determinant of the systematic variations of land surface elevation in the region, compared to the traditional idea, based on the tectonic elevation of the earth’s surface.”
A positive point or not?
Although the phenomenon seems to offer a natural shock absorber Against the rising sea level, Knight warns against too optimistic conclusions.
“Of course it can be said that if the earth’s surface is rising, then, in a relative sense, the level of the sea may be static or it may be down,” Knight said.
“But, of course, this can be done at the expense of less water present on the earth’s surface. In this case, if I had to decide between a decreasing sea level climb on the coast and a drought inside, I would choose the sea level as the least bad option. ”
Karegar adds that while some countries artificially increase the elevation of the earth injecting wastewater into the underground To reduce the risk of flooding, the situation of South Africa is a byproduct of natural drought.
Still, Karega states that study conclusions can help the broader environmental management.
“These findings can help improve drought and flood monitoring, guide groundwater management and inform a more strategic planning of water resources and climate adaptation efforts,” he said.
