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14/03/2018 - Mountains become islands: Ecological dangers of increasing land use in East Africa

Frankfurt am Main/ Germany, March 14, 2018. The mountains of East Africa are a treasure trove of biodiversity. However, their ecosystems may be at a higher risk than previously realized as researchers of the German Senckenberg Biodiversity and Climate Centre and the University of Bayreuth point out in a new study recently published “Global Change Biology”. The researchers have discovered that Mount Kilimanjaro is turning into an "ecological island". Agriculture and housing construction have eliminated the natural vegetation that used to serve as a bridge to the surrounding area, enabling the diversity of species to develop to its current levels. Neighbouring mountain regions are presumably also being isolated from their surrounding areas.

Kiimanjaro AHemp
View of the vegetation zones on Mount
Kilimanjaro, which is now almost completely
surrounded by agricultural areas. Photo: Andreas Hemp.

With a height of almost 6,000 metres, Mount Kilimanjaro is the highest mountain in Africa, and it is located less than 100 kilometres from the 4,600-metre-high volcano Mount Meru in northern Tanzania. Satellite images show how dramatically the strips of land between them have changed between 1976 and 2000.

Areas that originally were covered by dense vegetation were forced to make room for the intensive agriculture and residential development of a growing population. Nowadays, Mount Kilimanjaro is almost completely surrounded by large areas that are characterized by the encroachment of human civilization.

Bridges of vegetation promote the diversity of species
In order to investigate the impact this rapid change is having on biodiversity, biologists from the University of Bayreuth and the Senckenberg Biodiversity and Climate Research Centre Frankfurt studied the environments of grasshoppers at 500 selected sites on Mount Kilimanjaro and Mount Meru. In this investigation, endemic species – species that are only native to this region of East Africa – were of particular interest.

Kilimanjaro Landsat AHemp
Much of the natural forest vegetation between
Mount Meru and Mount Kilimanjaro vanished
between 1976 and 2000. Illustrations: Andreas Hemp.

The scientists found an especially high proportion of endemic species in the forest areas at lower altitudes shared by these two mountains. “This is a clear indication that grasshoppers once used the dense vegetation between the mountains as bridges to spread out in both regions.  Most notably, the wingless species relied on this land route”, says Dr. Claudia Hemp, Senckenberg Biodiversity and Climate Research Centre.

Conspicuously, there are also a few endemic species that are only found in higher forest areas. The answer lies in palaeo-ecological climate changes. "Several thousand years ago, it was considerably cooler and damper in the lower areas than it is today. Thus, grasshoppers that preferred these climatic conditions settled at the foot of the mountains, travelling by foot via the wooded land route. It was only later, as the temperatures rose and precipitation diminished that they made their way to higher areas. They then no longer had contact to grasshoppers in neighbouring regions," Dr. Andreas Hemp, University of Bayreuth explains.

The study also sheds light on the question of how the East African mountain ranges were settled during past climate periods. "Our research findings corroborate the thesis that animal and plant species spread out primarily via bridges of vegetation. Other ways of spreading over long distances, for instance seed transport via wind or the "air travel" of individual insects, must have played a subordinate role," Dr. Andreas Hemp continues.

Grasshopper Afroanthracites CHemp
Using grasshoppers (pictured species of
the genus Afroanthracites) researchers studied
how biodiversity onsite will be effected in the future
following the current ecological isolation of the
mountains. Photo: Claudia Hemp

Grasshoppers as early warning systems for endangered species
If bridges of vegetation between the mountains weaken or vanish altogether, it is not just the mobility of grasshoppers that is affected. Larger animals living in the forest – e.g. antelope, small mammals, snakes, or chameleons – are at an even higher risk of becoming isolated and thus going extinct in the foreseeable future.

Grasshoppers serve as an early warning system for researchers, signaling these kinds of far-reaching effects for other animal groups that are often difficult to study. "However, reliable statements about the ecological interrelationships are only possible after many years of scientifically demanding field studies," emphasizes Dr. Claudia Hemp.

Support for the research from natural history museums
The newly published study was funded by the German Research Foundation (DFG) and made possible by the support of research institutions in Tanzania and the cooperation of the natural history museums in Nairobi, London, Tervuren (Belgium), Berlin, Madrid, Stockholm, and Vienna. The museum stays were mainly funded by the Synthesis Project , which was in turn financed by the European Union.

This enabled the researchers to compare their evolutionary and taxonomical findings from their investigations of grasshoppers in Tanzania with the museums' insect collections. "Our study demonstrates the considerable scientific relevance of such natural history collections. The museums offer more than just fascinating insights into the diversity of species and the history of their evolution. They are also crucial for the investigation of ecological interrelationships in times of global anthropogenic changes," said Dr. Claudia Hemp.


Dr. Claudia Hemp
Senckenberg Biodiversity and Climate Research Centre & University of Bayreuth

Sabine Wendler
Press officer
Senckenberg Biodiversity and Climate Research Centre
Tel. +49 (0)69- 7542 1818


Hemp, A., Hemp, C. (2018): Broken bridges: The isolation of Kilimanjaro's ecosystem. Global Change Biology ,  doi: 10.1111/gcb.14078

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To study and understand nature with its limitless diversity of living creatures and to preserve and manage it in a sustainable fashion as the basis of life for future generations – this has been the goal of the Senckenberg Gesellschaft für Naturforschung (Senckenberg Nature Research Society) for 200 years. This integrative “geobiodiversity research” and the dissemination of research and science are among Senckenberg’s main tasks. Three nature museums in Frankfurt, Görlitz and Dresden display the diversity of life and the earth’s development over millions of years. The Senckenberg Nature Research Society is a member of the Leibniz Association. The Senckenberg Nature Museum in Frankfurt am Main is supported by the City of Frankfurt am Main as well as numerous other partners. Additional information can be found at www.senckenberg.de


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