Post by Peter on Jul 9, 2004 16:22:25 GMT
SOUTH AFRICA
Discovery of two 'extinct' Western Cape insects may signal ecosystem's recovery
July 7, 2004
By Melanie Gosling
Two little Cape damselflies - thought to have been extinct and one of them last seen 83 years ago - have been rediscovered in the Western Cape.
The insects, related to dragonflies, are believed to have made a comeback because invasive alien vegetation on river banks and around wetlands is being hacked down.
And if damselflies are coming back, scientists say, there is a good chance that the ecosystem in which they were found is also recovering, as they and dragonflies are used as indicators of riverine integrity.
Stuart Taylor, a University of Stellenbosch entymologist, said the damselflies were spotted by a scientist near Franschhoek late last year.
"He alerted us as he thought he may have found those that were thought to be extinct. When we saw them, we knew immediately they were," he said.
The last recorded sighting of the Cape Bluet was in 1962 and the smaller Ceres Stream damselfly in 1920.
Despite intensive searches, they were not seen again until last year.
"We've had students working on dragonflies and damselflies for a number of years and there is a wealth of information they've collected that shows invasive alien vegetation is driving these insects to death," Taylor said.
"Almost all insects are affected by alien vegetation. The aliens acidify streams and this has a knock-on effect and changes many other aspects of the environment."
Dragonflies and damselflies had been collected for study because they were sensitive to change. The main effect of alien vegetation, particularly wattles, on damselflies, was that it cut out the sunlight over the ponds and wetlands where the insects lived.
"Damselflies and dragonflies won't fly unless there is sunlight. It is an energy thing," Taylor said.
It is only in flight that the insects mate, so if they don't fly, their numbers are reduced.
Insect populations have been reduced because much of their wetland habitat has been drained for other uses. Insects are having an increasingly difficult time finding areas in which to live and breed.
Taylor said it was clearly critical to continue removing alien vegetation, particularly around water courses.
"Clearly the Working for Water programme is having a positive effect. When we see the insects coming back, we know the environment is responding positively to this human intervention. It shows it is recovering.
"South Africa has a enormous biodiversity, but a lot of it is being lost."
The saving of any indigenous species "was a good thing".
Source: Cape Times, www.capetimes.co.za/index.php?fSectionId=271&fArticleId=2140710.
Discovery of two 'extinct' Western Cape insects may signal ecosystem's recovery
July 7, 2004
By Melanie Gosling
Two little Cape damselflies - thought to have been extinct and one of them last seen 83 years ago - have been rediscovered in the Western Cape.
The insects, related to dragonflies, are believed to have made a comeback because invasive alien vegetation on river banks and around wetlands is being hacked down.
And if damselflies are coming back, scientists say, there is a good chance that the ecosystem in which they were found is also recovering, as they and dragonflies are used as indicators of riverine integrity.
Stuart Taylor, a University of Stellenbosch entymologist, said the damselflies were spotted by a scientist near Franschhoek late last year.
"He alerted us as he thought he may have found those that were thought to be extinct. When we saw them, we knew immediately they were," he said.
The last recorded sighting of the Cape Bluet was in 1962 and the smaller Ceres Stream damselfly in 1920.
Despite intensive searches, they were not seen again until last year.
"We've had students working on dragonflies and damselflies for a number of years and there is a wealth of information they've collected that shows invasive alien vegetation is driving these insects to death," Taylor said.
"Almost all insects are affected by alien vegetation. The aliens acidify streams and this has a knock-on effect and changes many other aspects of the environment."
Dragonflies and damselflies had been collected for study because they were sensitive to change. The main effect of alien vegetation, particularly wattles, on damselflies, was that it cut out the sunlight over the ponds and wetlands where the insects lived.
"Damselflies and dragonflies won't fly unless there is sunlight. It is an energy thing," Taylor said.
It is only in flight that the insects mate, so if they don't fly, their numbers are reduced.
Insect populations have been reduced because much of their wetland habitat has been drained for other uses. Insects are having an increasingly difficult time finding areas in which to live and breed.
Taylor said it was clearly critical to continue removing alien vegetation, particularly around water courses.
"Clearly the Working for Water programme is having a positive effect. When we see the insects coming back, we know the environment is responding positively to this human intervention. It shows it is recovering.
"South Africa has a enormous biodiversity, but a lot of it is being lost."
The saving of any indigenous species "was a good thing".
Source: Cape Times, www.capetimes.co.za/index.php?fSectionId=271&fArticleId=2140710.
