/ 30 July 2010

Gauteng boom leaves goggas homeless

As housing developments spread across the grasslands of Gauteng, insects are being pushed out of their homes. And when that happens, they fade away.

The Gauteng gogga is in rapid decline, a new scientific study has found.

It estimates that in the last decade there has been a 30,3% loss in biodiversity integrity in Gauteng and its surrounds.

However, Pretoria entomologists Peter Hawkes and Max Clark, who conducted the study for the Oppenheimer family, consider this to be an underestimate.

Their study is bad news for the environment, because insects often play a critical role in keeping eco-systems healthy.

The Gauteng department of agriculture and rural development has shown an interest in using the study to influence provincial government policy and future environmental impact studies.

The two scientists were commissioned by matriarch Strilli Oppenheimer, who has long been concerned about whether insect life is fading in Gauteng.

Finding the reason does not require rocket science: as development takes over the veld, the insects have nowhere to go.

“Anecdotal evidence suggests that there has been a substantial decline in insect populations in Johannesburg, Pretoria and surrounding areas over the past 30 years, but no scientific studies have been carried out to support this — it is the sort of thing that everyone ‘knows’ but no one can prove,” said the two scientists.

They said the decline in insect life could have profound consequences for the long-term viability of ecosystems in Gauteng.

Insect diversity and abundance were investigated at 24 sites in the province, covering grasslands, koppies, populated areas near cities, new developments and wetlands. Most of the sites were indigenous grasslands.

The scientists also looked at whether cellular phone towers could possibly have an affect on the insect population decline, but found insufficient evidence to support this theory.

“Any impacts that might occur are probably completely overshadowed by the effects of habitat transformation resulting from urbanisation and agriculture,” said Hawkes.

The two scientists found that ground-dwelling beetles were especially susceptible to habitat loss, because many species cannot fly off to find new homes.

They also found that larger insect species, measuring more than 2cm in length, were more common in larger habitats further away from urban centres. Such species have all but disappeared from the province’s city environment.

Worryingly, bee biodiversity has also declined slightly with increasing habitat disturbance, the scientists found.

Hawkes and Clark identified 194 ant species in Gauteng, of which at least five are new to science.

“Ant diversity and abundance were strongly influenced by the degree of habitat disturbance and transformation and to a lesser extent by habitat patch size,” they said.

“The most significant impact on ant populations resulted from intensive monocrop agriculture.”