Researchers from the University of Hamburg, including biologist Prof. Dr. Norbert Jürgens and soil scientist Dr. Alexander Gröngröft, have confirmed that the phenomenon of circular barren patches in the African grasslands, commonly referred to as fairy circles, are created by sand termites. This evidence negates prior theories suggesting that these circles were the result of grasses regulating themselves to store water.
For many years, the formation of fairy circles in Africa’s grasslands has intrigued scientists. A recent study led by Jürgens and Gröngröft validates that the origin of these circles lies in the activity of sand termites, specifically those belonging to the Psammotermes genus.
Simultaneously, the researchers have refuted the primary claims made by ecosystem modelers who had previously argued that these barren patches are a consequence of self-regulation mechanisms in grass plants.
As far back as 2013, Jürgens had published a paper in Science stating that the sand termites create these patches by eliminating vegetation in the sandy soils, allowing the soil to retain water for an extended period following infrequent rainfall. This theory was subsequently confirmed by entomologists from southern Africa including Prof Mike Picker, Dr. Joh Henschel, and Dr. Kelly Vlieghe.
Research teams from other institutions, such as the University of Göttingen, also investigated this phenomenon using computational models. Their publications suggested that the grass plants draw water unevenly through their root systems, thereby creating these barren patches. They pointed to soil desiccation measured at a depth of 20 cm beneath the fairy circles as evidence supporting their claims.
However, in their latest article published by Perspectives in Plant Ecology, Evolution and Systematics, Jürgens and Gröngröft examined more than 1,700 fairy circles across Namibia, Angola, and South Africa and found sand termites in each one. The soil moisture measurements cited by the Göttingen team in 2022 were compared with Jürgens’ own measurements from 2013. Jürgens demonstrated that the circles can store water over a long period, based on simultaneous measurements at varying depths up to 90 cm.
More critically, the research from Gröngröft, involving laboratory measurements of hydrological properties of desert sand, discredited the underlying premises of the self-regulation hypothesis. Gröngröft found that while the soil can quickly absorb a large amount of water during heavy rainfall, the soil’s capacity to transfer water diminishes considerably once it dries to less than about eight percent of its volume. Consequently, the soil under the fairy circles retains very little moisture (≤5% by volume), negating the possibility of rapid horizontal water transport over short distances.
Jürgens states that the self-regulation theory is therefore rendered implausible based on current understanding of soil physics. The moisture measurements and laboratory analyses have eliminated self-regulation as a viable explanation for the formation of the fairy circles. Their research concludes that it is the activity of sand termites that allows for significant water storage in the soil, providing them with a considerable survival advantage.
Reference: “Sand termite herbivory causes Namibia’s fairy circles – A response to Getzin et al. (2022)” by Norbert Jürgens and Alexander Gröngröft, 3 June 2023, Perspectives in Plant Ecology, Evolution and Systematics.
DOI: 10.1016/j.ppees.2023.125745
Table of Contents
Frequently Asked Questions (FAQs) about Fairy Circles
What is the primary focus of the research conducted by the University of Hamburg?
The primary focus of the research is to identify the cause behind the formation of fairy circles, which are mysterious circular barren patches found in African grasslands.
Who are the main researchers involved in this study?
The main researchers are biologist Prof. Dr. Norbert Jürgens and soil scientist Dr. Alexander Gröngröft from the University of Hamburg.
What theory does this research debunk?
The research debunks the prior theory that these fairy circles are formed due to the self-regulating behavior of grass plants in African grasslands.
What organism is identified as the cause of the fairy circles?
Sand termites, specifically from the genus Psammotermes, are identified as the cause of the formation of these fairy circles.
What alternative explanations had been proposed before this research?
Before this study, researchers had proposed that the circles might be caused by self-regulating mechanisms in grass plants, which drew water unevenly through their root systems.
How does this study refute the self-regulation hypothesis?
The study refutes the self-regulation hypothesis through empirical evidence gathered from more than 1,700 fairy circles and soil moisture measurements. Moreover, laboratory analyses of the hydrological properties of desert sand were also presented to discredit the underlying premises of the self-regulation hypothesis.
Where were the fairy circles studied?
The fairy circles were studied across Namibia, Angola, and South Africa.
What is the significance of soil moisture measurements in this research?
Soil moisture measurements are critical as they demonstrate the long-term water storage capabilities of the fairy circles. These measurements also help in debunking the self-regulation theory by showing that quick horizontal water transport over short distances is not possible in the observed soil conditions.
What are the survival advantages for sand termites in creating these fairy circles?
The sand termites gain a considerable survival advantage by creating these fairy circles as the soil within them retains significant amounts of water, providing the termites with a more stable environment.
When and where was this research published?
This research was published on 3 June 2023 in the journal “Perspectives in Plant Ecology, Evolution and Systematics” with the DOI: 10.1016/j.ppees.2023.125745.
More about Fairy Circles
- Original Research Article in Perspectives in Plant Ecology, Evolution and Systematics
- University of Hamburg Research Department
- Prof. Dr. Norbert Jürgens’ Academic Profile
- Introduction to Fairy Circles
- Previous Studies on Self-Regulation in Plants
- Psammotermes Genus Information
- Overview of African Grasslands
- Soil Science and Hydrological Properties
