Plants Adapt to Ozone Threat

By JAMIESON, Debbie

Food plants across the world are developing a poisonous protective layer to shield against harmful ultraviolet (UV) rays, scientists studying the effects of ozone depletion say.

The discovery has turned traditional thinking on its head, according to international experts on the environmental effects of ozone depletion gathered in Alexandra this week.

The 24 scientists are tasked with reporting changes to the ozone layer and subsequent consequences to the United Nations.

Until recently, it has been assumed that UV radiation only had a negative effect on plants — but it is now recognised that a screening pigment produced by most plants can be toxic to predators and help with disease prevention.

Now attempts are being made to harness that information to produce stronger and more natural food crops.

Dr Nigel Paul, of Britain, is already engaged in trials, funded by the Department of Agriculture, looking at reducing pesticide use on soft-root crops such as strawberries, blackcurrants and vegetables.

“In Europe, consumers really want produce untreated by pesticides. If growers can deliver that, it’s a real bonus,” he said.

No negative effects on humans have yet been identified, and some of the toxins have even been found to contain beneficial anti- oxidants.

They could also prove to be a big leap forward for organic growers, he said.

The only warning bells ringing are over the effects the increased levels of toxins might be having on the wider food chain, he said.

The scientists meeting in Alexandra are also concerned with the effects ozone depletion is having on the increasing incidence of skin cancer and cataracts on humans, the damage to the functioning of oceans, air quality and the degradation of plastics used in building.

Panel co-chairpersons Dr Jan van der Leun, of the Netherlands, and Professor Janet Bornman, of Denmark, said the production of chlorofluorocarbons, the substance that has caused most of the damage to the ozone layer, had reduced by 90% in recent years, enabling the ozone layer to begin recovering.

Now the knowledge was developing faster than the problem.

The biggest risk to that recovery, estimated to take 60 years, was unpredictable climate change and carbon dioxide emissions and their interaction with the ozone layer.

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