By geologist Dr. Sebastian Luning and Prof. Fritz Vahrenholt.
(German text translated/edited by P Gosselin)
On August 25, 2016 there was in Nature Climate Change a small wonder was observed. A team of scientist led by Gennadii Donchyts of the Dutch Deltares Research Institute released a statistic on land area gain and loss in the coastal areas on earth. Given our rising sea levels, a loss of land area was expected. Thus the surprise was even more profound when the official figures were released: coastal regions didn’t shrink, rather they grew by 13,565 sq km over the past 30 years.
That’s a real sensation.
Unfortunately the German media chose to keep silent about it. Inconvenient data that they do not want the public to see. In the publication it is stated:
Earth’s surface gained 115,000 km2 of water and 173,000 km2 of land over the past 30 years, including 20,135 km2 of water and 33,700 km2 of land in coastal areas. Here, we analyse the gains and losses through the Deltares Aqua Monitor — an open tool that detects land and water changes around the globe.
For what is interesting are the figures for the coastal areas (the other figures concern inland bodies of water that are independent of sea level). The calculation is trivial:
33,700 sq km of land gain minus 20,135 sq km of land loss = a net land gain of 13,565 sq km.
The people at the Deltares-Institute did have some fear of the figures. In the original press release, they refrained from presenting this important result:
How the earth has changed over the past 30 years
The world has gained 115,000 km2 of water and 173,000 km2 of land over the past 30 years. The Dutch research institute Deltares developed an open tool that analyses satellite data and visualises land and water changes around the globe. The results were published today in Nature Climate Change.
First global-scale tool that shows water and land conversion
The Deltares Aqua Monitor was developed by Gennadii Donchyts, a remote sensing expert at Deltares. It is the first global-scale tool that shows, with a 30-metre resolution, where water has been transformed into land and vice-versa. The Aqua Monitor uses freely available satellite data and Google Earth Engine, a platform for the planetary-scale scientific analysis of geospatial datasets that is now open to the general public. Gennadii Donchyts: “The Aqua Monitor shows that, around the world between 1985 and 2015, about 173 000 km2, an area about the size of Washington State, has been transformed into land. At the same time, an area of 115 000 km2 has been transformed into water. Both documented and undocumented changes due to man-made interventions, natural variability, and climate change have now been revealed.”
Known versus unknown
While many countries report on dam construction, information about more remote or isolated areas has been lacking. In Myanmar, the Global Reservoir and Dams database shows an increase in the water surface between 1985 and 2010 of about 400 km2. Using the Aqua Monitor, we found 1,180 km2 of new surface water during the same period. The damming of the Rimjin River in North Korea close to the border with South Korea resulted in a storage surface of 12.4 km2 that was actually due to the Hwanggang Dam, which was thought to be located 35 km to the east. These unknown reservoirs may have had a severe impact on the displacement of people and on the ecology. These issues still have to be investigated.
Created by nature or humans
The results of the Aqua Monitor show only the compound impact of natural and human change or variability. It is often hard to tell what has caused a change without determining the details of the local water and sediment budget. While changes in meanders in the Brahmaputra delta are clearly natural, the Mondrian-like shapes near Taiji Nai’er lakes in China are clearly man-made.
Big data at everyone’s fingertips
Universally-available analytics for big satellite data may have major implications for monitoring capacity and associated actions. At the very local scale, members of the general public can now make assessments without expert assistance if their houses are threatened by coastal erosion. At the regional scale, a downstream riparian state can conduct year-to-year monitoring to see whether upstream neighbours are establishing new impoundments. Finally, at the planetary scale, global agencies such as the United Nations International Strategy for Disaster Reduction can monitor the appearance of new reservoir storage capacity that may reduce flood hazards.
Jaap Kwadijk, the Deltares scientific director: “This has never been done before. So it is difficult to imagine all the new applications that will be made using this tool. But the tool can be used by everybody and so I am sure multiple applications will emerge in the next few years”.
The BBC took on an approach of transparency and reported explicitly on the land area gain at the coasts:
Coastal areas were also analysed, and to the scientists surprise, coastlines had gained more land – 33,700 sq km (13,000 sq miles) – than they had been lost to water (20,100 sq km or 7,800 sq miles). “We expected that the coast would start to retreat due to sea level rise, but the most surprising thing is that the coasts are growing all over the world,” said Dr Baart. “We’re were able to create more land than sea level rise was taking.”
Why is the result so? Every geologist learns in the first semesters that deltas expand out into the sea when the rate of sediment buildup is faster than then sea level rise. This appears to be the case here. Sea level rise is too small to lead to a flooding of coastal level areas. The system finds itself in a state of regression as many sand coasts are pushing out slowly into the sea.
Policymakers need to take Geology 101
After the end of the last ice age some 10,000 years ago, the case was very different. Back then sea level rise was multiple times greater than what it is today and coasts were covered by the sea. In geological terms this is called “transgression”. Perhaps political policy makers should be required to take Geology 101 so that they are better able to take part in the climate discussion.