| World sickens as heat rises Infections in wildlife spread as pests thrive in climate change Tim Radford, science editor Friday June 21, 2002 from :The Guardian Climate change is favouring pests and parasites and triggering widespread outbreaks of disease in wildlife, according to US scientists. Warmer summers and milder winters are encouraging disease-bearing infections that blight coral reefs, kill shellfish colonies, and threaten lions, cranes, vultures and even ferrets. The global warming is also helping to spread tropical diseases to human habitations previously unaffected by such illnesses, they report in the journal Science today. "This is not just a question of coral bleaching for a few marine ecologists, nor just a question of malaria for a few health officials. The number of similar increases in disease incidence is astonishing," said Richard Ostfield, of the Institute for Ecosystem Studies, in Millbrook, New York. Andrew Dobson, of Princeton University, said: "The accumulation of evidence has us extremely worried. We share diseases with some of these species. The risk for humans is going up." Frosts and cool periods can cut insect, parasite and fungus pest populations by up to 99%. But mellow winters, followed by long spells of warmth and humidity, provide perfect conditions for their survival. Ecologists and health officials began predicting years ago that mosquitoes, ticks, rodents, viruses, fungi and bacteria were likely to spread into other areas as temperatures rose, with potentially devastating effects on wildlife. In Hawaii, avian malaria has already wiped out native song birds living below an altitude of 1,400 metres (4,500ft); 30 years ago, the malarial mosquitoes only survived up to an altitude of 800 metres. The team, led by Drew Harvell, of the ecology and evolutionary biology department at Cornell University, also used the hotspots of El Nino - the dramatic cyclic increase in the warmth of the tropical Pacific ocean that also affects African and American climate patterns - as a guide to climate trends. The scientists looked at the massive die-off of corals during the unusually warm El Nino year of 1998. Much of the coral had died from fungal and other diseases thriving in warmer seas. Oysters in Maine, in the US, had been blighted by parasites normally restricted to more southerly waters. Lions in the Serengeti had suffered canine distemper, and cranes, vultures and even wild American ferrets had been hit by disease outbreaks. The monarch butterfly came under pressure from an exploding parasite population. Rift valley fever, a devastating viral illness of cattle and humans, spread by mosquitoes, also spread during the hot El Nino year of 1998. In a warmer world, such events could occur more regularly: viruses in the mosquito population would multiply , and so too would the mosquitoes. The scientists fear that the spread of tropical infections to temperate zones could have even more calamitous effects. The tropics, compared with other geographical regions, have a richer variety of species and fewer individuals in each species; diversity acts as a buffer to the spread of disease. But temperate zones have a smaller range of species, with greater numbers in each, so pathogens moving into the temperate zones could affect a few common and abundant susceptible species. "And human destruction of biodiversity makes this a double whammy. It means we are exacerbating the problem," said Dr Dobson. "We have to get serious about global change. It is not only going to be a warmer world, it is going to be a sicker world." |
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