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Traces of deadly pesticides found in Breede River fish eagles

Although the deadly pesticides DDT and Dieldrin were banned in 1980, researchers have picked up traces of these poisons in fish eagles along the Breede River Valley.

They have also found traces of the pesticides now used on the farms in the valley. But the good news is that the amounts of pesticides they have detected are very small and appear to have had no harmful effects on these top predators.

At a briefing yesterday, researchers explained that the purpose of the fish eagle research project was not fish eagle conservation, but to establish the extend to which chemical pollution was permeating the Breede River system.

UCT ornithologist, Andre Jenkins, said several researchers were collaborating on the Breede River Fish Eagle Project sponsored by Flight of the Fish Eagle Brandy. The valley stretched about 300km from Tulbagh to Witsand.

"It's a very intensely farmed area, and there is a lot of pesticides use, but very little has been done on the effects of these pesticides on the environment. We know that pesticides accumulate in top predators, and that fish-eating and bird-eating birds are particularly prone to the bio-accumulation, where the levels of contamination are magnified," Jenkins said.

"By looking at the accumulations in fish eagles, we are likely to get a handle on the extend to which pesticide accumulation is a problem in the region, much as the bold eagle was used in similar research in the US," he said.

So far, the residues of pesticides and heavy metals found in blood and feather samples of the birds have been harmless. However, the project was still in its initial stages and it would take some time before the researchers had developed a chemical pollution profile for the entire Breede River catchment area.

"Once that has been completed, it will be able to inform decision-makers of the impact of agro-chemical pollution of South Africa's aquatic ecosystem," Jenkins said.

UCT researcher, Adam Welz, said Dieldrin, DDT and Lindane pesticides, now banned, had been used in the Karoo before 1980, but not in the Breede River Valley.

"But we have picked up traces in the fish eagles, which means those pesticides must have made their way from the Karoo, about 300km away, into the Breede River study area. That shows how long they stay in the environment, how long they take to break down," Welz said.

The current pesticides used in agriculture took only about two or three days to break down. "But the danger is they are far more toxic, so we need to monitor their effects. Despite the huge amounts of pesticides that are being used in the valley, there are no indications that fish eagles are being harmed," said Welz.

Article written by Melanie Gosling and published in the Cape Times on 25 May 2007