Mass die-offs set to be a gruesome feature of global warming

Even small temperature rises could have devastating results

August 2010: This shocking picture shows how a flock of budgerigars literally dropped dead during a heatwave in Western Australia. It is not the only incident of its kind, with similar die-offs increasingly common across both India and Australia during periods of extreme hot weather.

MASS DEATHS: Budgerigars drop dead in the heat in Western Australia

Tragically, according to the latest research, this looks set to become a growing phenomena world wide as global warming takes its toll, with relatively minor temperature changes having major dramatic effect.

Blair Wolf, an associate professor of biology at the University of New Mexico, and his collaborator Andrew McKechnie from the University of Pretoria, South Africa, have been studying how increasing global temperatures will impact desert bird populations. They have found that during heat waves, increases in air temperatures of as little as two degrees Fahrenheit can double the rate of water loss in a small bird and importantly impact its survival time.

The Intergovernmental Panel on Climate Change (IPCC) predicts that the average temperature of the planet will rise between 3.5 and 6.5 degrees Fahrenheit (2 to 4 degrees centigrade) over the next 100 years. This may not seem like much, but according to Wolf, these changes could be disastrous for birds and some mammals because of the increased intensity and frequency of heat waves that will result.
This is due in part to the fact that when environmental temperatures are above air temperature, birds and other animals have to get rid of body and environmental heat by evaporating water across the skin and by panting.

Evaporative water loss increases rapidly with increasing temperature and excessive water loss reduces a bird's ability to stay cool. The resulting high body temperatures can produce heat stroke, which causes damage to body tissues, organ failure and blood clotting that quickly lead to death.

Wolf and McKechnie examined the effects of increased global temperatures and more intense heat waves on the water budgets of desert birds of differing sizes. They used a mathematical model to predict the future water costs for birds living during heat waves in the 2080s compared to the current costs for two hot desert regions, Yuma, Arizona and Birdsville, Australia. Their research shows that during heat waves in the 2080s, small birds will show greater increases in water loss rates than larger birds leading to greatly reduced survival times in small birds. For small birds, survival times may be reduced by as much as 30-40 per cent.

Die-offs are already becoming ‘routine'
For small birds the increase rate in water loss may decrease their survival time by a much as a quarter - meaning that the heat may simply be overwhelming and they may not be able to keep their body temperature below lethal levels.

‘This is what appears to be happening almost routinely in Western Australia and India now,' says Wolf.

Incidents of large die-offs have occurred in Australia and India and were reported by the regional news media or by the locals. A similar phenomenon has also been noted with fruit bats dropping from the trees during heat waves in Eastern Australia.

‘We don't have good research on these die-offs,' says Wolf. ‘No researchers have actually been present during these incidents and no one has actually done the autopsies - so we don't even know the exact cause of death of these animals, whether it was dehydration or heatstroke.'

Local knowledge suggests that die-offs can result in the loss of some species from regions for decades and the long-term effects these die-offs have on other groups of plants and animals are as yet unknown. ‘These incidents illustrate a need for more basic research on how animals function so that predictions can be made and measures can be taken to preserve our biodiversity,' says Wolf.