Kangaroo plague threatens Australia's grasslands

Researchers are studying consequences of the condition

Gray giant kangaroo © Anett Richter / UFZ
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Australia's capital Canberra is plagued by a kangaroo invasion. The heraldic animal of the country has increased so much in recent years that the metropolis now has three times more kangaroos than inhabitants. Particularly dramatic is the situation on two fenced military areas on the outskirts, which serve the Eastern Gray Giant Kangaroo as an ideal retreat area. The grasslands there are now completely overgrazed - with dramatic consequences for other species.

Because these areas are among the few natural grasslands in Australia and are therefore one of the remaining reserves for endangered species such as the sun moth - Synemon plana - or the earless grassland kite - Tympanocryptis pinguicolla - one of the rarest lizard species ever. For several years, researchers from Canberra and Leipzig have been researching the consequences of landscape fragmentation and changes in use on biodiversity.

To the cityscape of Canberra, also called "Bush Capital" of Australia, the gray marsupials have always heard. But even the numbers of Leipzig biologists Anett Richter and Dr. Marion Höhn from the Helmholtz Center for Environmental Research (UFZ). Anett Richter investigates how grasshoppers, ground beetles and cicadas in the natural grasslands of the Australian Capital Territory (ACT) are affected by landscape fragmentation.

Dry meadows and kangaroo lot

But in their field work, they found that there were far fewer of them than expected. What she found instead was bald eaves, withered meadows marked by the drought of the century, and large quantities of kangaroo kot, especially in the fenced military areas: "The results of the fragmentation investigations are not yet available. But we assume that there is an association between the extremely high population densities of kangaroos and the diversity of invertebrate species on individual areas, especially in times of severe drought. "

But man is not innocent either. The once extensive grasslands were the territory of the Australian aborigines, who used this sensitive ecosystem sustainably through hunting and fire management. Natural predators like the dingo controlled the population sizes of kangaroos. With the colonization of Australia 200 years ago, the grasslands were first lost and the development of cities led to a complete change in the landscape structure. Today, as a result of urbanization and intensification of the countryside, Australia is largely a highly fragmented landscape with a high risk of losing its biodiversity. As a result of the dramatic droughts of the last ten years, there was a continuous overgrazing of natural grasslands, which could not recover. display

Man, however, has considerably improved the supply of water for K ngurus by cultivating livestock wards and other bodies of water. Normally, the weaker K ngurus of drought fall victim to drought. Today, however, they can resort to artificial water points and thus preserve their existence, which further damages the already impaired vegetation. In contrast to other species, the K ngurus have adapted well to humans.

Grasslands continue to disappear

Australia's capital is a prime example of how much man has changed the fifth continent since European settlement over 200 years ago. Where Canberra today stretches, there were previously natural grasslands that once formed the image of southern Australia. Of this, five percent remained in the capital territory and only one percent in the whole of Australia. And even these small, isolated areas are now threatened by the K ngurus, by building or by the D rre out. Only a few years ago, the inhabitants of the capital could rejoice over the rediscovery of a lost roommate.

Earless Prairie Dragon Wendy Dimond / University of Canberra

The earless grassland dragon is one of the rarest reptile species in the world. Only a few populations on the edge of Canberra have survived. The tiny lizard, weighing just nine grams, knows how to camouflage itself so well that it was considered extinct for a long time. Until 1991, the biologist dr. Will Osborne, of Canberra University, accidentally shoved a stone aside with his foot, "What suddenly appeared underneath was one of the most exciting moments in my life. I still do not know how I managed to get my little son off his shoulders so quickly to jump the lizard after and catch her. "

Listen without ears

For thirty years, the lizard with no ears, which can still hear, was considered lost. "But it's difficult to create plans to protect a species about which little is known, " says rediscoverer Osborne. Over the last few years, his colleagues and researchers from the Helmholtz Center for Environmental Research (UFZ) in Leipzig have therefore been investigating the lifestyle of the reptile in order to better understand the grassland ecosystem. Like the dragon in the fairy tale, the earless grassland dragon has a cave. Spaces of spiders on the meadow floor make for the ideal hiding place where the lizards can survive even bush fires. Only they are so little mobile and threaten to be the victim of the changes in the landscape.

Marion H hn is investigating in genetic studies whether the earless grassland dragon populations are interchangeable: "If not, there is a risk in the longer term that inbreeding can lead to the extinction of the tiny populations." First, however, they must first survive the next few years. This includes a sufficient food base of insects, which in turn depend on the vegetation.

Various studies have been taking place in Canberra for some time to find efficient methods of birth control of the K ngurus. But by the time scientists have found regulatory mechanisms, it can be too late for many endangered and often overlooked species. For this reason, there seems to be no way around now to professionally shoot many kangaroos to protect the sensitive flora and fauna on the outskirts of the Australian capital.

(idw - Helmholtz Center for Environmental Research - UFZ, 18.05.2007 - DLO)