Climate change is favoring pests and parasites and triggering widespread outbreaks of disease in wildlife, according to U.S. 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 reported in the journal Science on June 21.
"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 percent. 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 meters (4,500 feet); 30 years ago, the malarial mosquitoes only survived up to an altitude of 800 meters (2,500 feet).
The team, led by Drew Harvell, of the ecology and evolutionary biology department at Cornell University, also used the hotspots of El Niñothe dramatic cyclic increase in the warmth of the tropical Pacific Ocean that also affects African and American climate patternsas a guide to climate trends.
The scientists looked at the massive die-off of corals during the unusually warm El Niño year of 1998. Much of the coral had died from fungal and other diseases thriving in warmer seas.
Oysters in Maine, in the U.S., 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 Niño 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.