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Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
An international research team led by the University of Hamburg has documented desertification on a scale never before seen in sub-Saharan Africa. This change threatens the South African Richtersveld, a globally significant biodiversity hotspot with many endemic plants, also highly valuable for local pastoralism. The study has now been published in the Journal of Arid Environments.
The images from South Africa are reminiscent of the devastation caused by the famous “Dust Bowl” in the Midwestern United States, which contributed to the Great Depression in the 1930s: formerly valuable pastureland is covered under sand, abandoned farmhouses are buried by dunes. In most areas of the Richtersveld in South Africa, there has been a decline in overall vegetation and biodiversity. Botanists and soil scientists from the University of Hamburg, together with colleagues from South Africa and Namibia, have shown this change with data going back up to 45 years. That is how long they have been monitoring the area of ca. 10.000 km².
Together, the scientists analysed the composition and quantity of plant species on designated monitoring areas at regular intervals. They also evaluated time series of satellite images, and during 2025 they repeated photos that were first taken in 1914.
"At first, it seemed as if the vegetation would always return to its original state despite all the fluctuations. But now we have discovered that a gradual impoverishment of the plant world began decades ago and continues even after the end of the recent extreme drought, which lasted a full ten years, from 2012 to 2022," explains Prof. Dr. Norbert Jürgens. The emeritus biologist has been conducting research in the area since February 1980. Soil scientist Dr. Alexander Gröngröft, also a researcher at the University of Hamburg, has been studying changes in the soil since 1992.
The researchers discovered that the species loss always follows a similar sequence of states. First, formerly densely vegetated pastureland loses its most ecologically important species: long-lived, water-storing dwarf shrubs that cover the ground and can hold wind-borne sand and dust. Then, sparsely growing, salt-loving plant species replace the succulents that are crucial to the ecosystem. And because the subsequent vegetation cannot permanently protect the soil surface, the fertile soil is carried away by the wind, creating vegetation-free sandy areas that are hardly colonized even after rainfall. The change in the soil becomes a tipping point for the change of biodiversity.
One thousand plant species are endemic, i.e. they occur exclusively in the Richtersveld, a large number compared to the less than 100 endemic species in Germany. 400 of the species are listed as threatened. These are estimates are made by another co-author of the study, Pieter van Wyk, Curator of the South African In-situ conservation and research garden Richtersveld Desert Botanical Garden.
Researchers attribute the degradation in part to climate change, which damages plants through higher temperatures, higher wind speeds, and longer periods of drought. However, they also found that in human activities cause significant desertification. Mining companies searching for diamonds usually leave mining pits and trenches uncovered, mobilizing large quantities of sand. When carried by the wind, the sand grains act like a sandblaster, damaging vegetation and burying it beneath the sand. Temporary overgrazing by goats, sheep, and cattle also triggers sand and dust transport in many places.
“In some areas, the combination of drought, overgrazing, and frequent strong winds has already led to irreversible changes in soil properties in this sensitive and globally unique ecosystem,” says Prof. Jürgens. This is particularly noticeable on 26,000 hectares in the north of the area, where succulent shrubs are being replaced by sparse desert grasses. In the south and west more than 400 km² have been buried under sand.
To combat desertification, scientists are proposing a package of measures, including strict control of mines and restrictions on grazing. Particularly vulnerable regions should be placed under nature conservation – without any land use or off-road driving. These rules must also apply to the numerous projects planned in the region for the generation of renewable energy from photovoltaics and wind, they demand. For even if these are considered green investments in the global North, they could -depending on planning – either cause further devastation or contribute to the renaturation of degraded areas.
Prof. Dr. Norbert Jürgens
Universität Hamburg
Fachbereich Biologie
Tel.: +49 170 1666500
E-Mail: norbert.juergens@uni-hamburg.de
https://authors.elsevier.com/sd/article/S0140-1963(25)00143-0
https://www.uni-hamburg.de/newsroom/presse/2025/pm30.html
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