Invasive species put dragonfly in the shade

09 March 2009 | News story

The Yellow Presba is a rare dragonfly from the fast flowing mountain rivers of southern Africa. Its conservation status is Vulnerable on The IUCN Red List of Threatened Species™ because of the spread of introduced trees throughout its native habitat.

The Yellow Presba (Syncordulia gracilis) is one of many southern African dragonflies currently under threat. Others have also suffered catastrophic declines because of human related problems like pollution, habitat loss to farming and the introduction of non-native trees. The spread of invasive species is now recognized as one of the greatest threats to the environment and our economic well-being. Trees such as the Australian Black Wattle (Acacia mearnsii), that were introduced commercially, encroach along riverbanks and shade out the sun, killing off the grasses that are home to dragonflies. The tragedy of losing these creatures is magnified to a global scale because many are endemic to southern Africa and can be found nowhere else on Earth.

Dragonflies have important roles in freshwater ecosystems, as predators of mosquitoes and other insects, and as a source of food to larger animals. They also act as valuable indicators of healthy aquatic environments because their larvae need clean water to survive. Regardless of their importance the conservation of dragonflies has often been neglected in southern Africa in the face of development.

To help inform the development process about the conservation of freshwater habitats, the IUCN Species Programme has worked with South African institutions to conduct a regional assessment of the status and distribution of 1,279 types of freshwater species including dragonflies, fishes, molluscs, aquatic plants and crabs. The results of this study form part of a larger project spanning the whole of Africa, creating a baseline of information for conservationists and development planners to account for the needs of freshwater species.

It was as part of this project in 2007 that the Yellow Presba was assessed and categorized on The IUCN Red List as Vulnerable. Having established that alien trees were a key threat, it was then possible for the IUCN Species Survival Commission (SSC) Dragonfly Specialist Group to target areas with alien trees and remove them in large numbers, as part of the government-sponsored ‘Working for Water’ Programme. The results were spectacular. The conservation status of the Yellow Presba has now stabilized, and the extinction of many other highly local species has also been averted.

The report of the ‘The status and distribution of freshwater biodiversity in southern Africa’ is launched on March 19th and will make further suggestions for focusing conservation action based on its findings.