Ozone blues

Forest and Bird, Volume 23, Issue 2, 1 May 1992, Page 9

Ozone blues

A MEETING of scientists from 25 countries has concluded that the ozone layer will continue to decline at least as fast in the 1990s as in the previous decade. The UN-sponsored meeting held earlier this year in Switzerland was reviewing the first complete study of the ozone layer since 1986. The report found that:

* the ozone layer is declining in all latitudes outside the tropics; and ¢ the overall decline between the latitudes of 65° north and 65° south — most of the inhabited world — was 2.5 percent over the past decade. The scientists opposed the use of hydro-chlorofluorocarbons (HCFCs), now being introduced as substitutes for CFCs. While only about one-tenth as dangerous as CFCs, HCFCs still pose a considerable threat to the ozone layer. Then, in March, NASA scientists discovered the beginning of an ozone hole at high northern latitudes. The immediate culprit is thought to be the eruption last year of

Mount Pinatubo in the Philippines. The eruption produced a high-altitude cloud of dust and acid droplets circulating in the northern hemisphere. This cloud is capable of accelerating the depletion of the ozone layer already burdened with synthetic compounds such as CFCs. Even cautious estimates suggest that a quarter to 40 percent of the ozone layer over Europe will be lost before it begins to repair itself with the onset of summer in June. This would be almost as bad as the 50 percent ozone loss now regularly recorded over Antarctica.

The Pinatubo particles will also gradually make their way into the southern stratosphere. Dr Tom Clarkson from the New Zealand Meteorological Service says that the ozone depletion rate over New Zealand will accelerate over the next two years from 0.5 percent to perhaps 4 percent a year before dropping back again as the volcanic particles fall out of the sky. The threats of increased ultra-violet radiation from a depleted ozone layer are not restricted to melanomas and cataracts in humans. Ultraviolet also damages plant DNA. Early spring, when ozone is at its most depleted and when plants are putting on new growth, is when they

are at their most vulnerable. Studies on Antarctic plankton suggest that because UV radiation harms some species more than others the balance within ecosystems may be changed. The US and European governments have now brought forward their phaseout dates for CFCs to 1995. New Zealand Environment Minister Rob Storey says that New Zealand will re-exam-ine its timetable. No decisions have been made, however, to accelerate the phase out of HCFCs which, under the Montreal Protocol, can continue to be made until 2040.