Science and Technology Avian malaria and climate change Bite the birds
科技 禽虐与气候变化 鸟类受害
Malaria among birds is becoming more prevalent
MOSQUITOES, which carry malaria parasites, like the warm and wet conditions that are expected to become more common with climate change.
This has led many to reason that malarial infections will increase.
Yet studies run into the unreliability of modelling future climatic effects and sometimes ignore changes in land use and health care.
However, a new analysis of the spread of avian malaria shows that for the birds, at least, there is a real worry.
Laszlo Garamszegi, of the Do?ana Biological Station in Spain, studied patterns of malarial infections in birds to avoid confounding human factors in determining the epidemiology of a closely related parasite.
He looked at 43 previous studies that had carefully screened 3,000 bird species for malaria in different locations over the past 70 years.
He found that an increase in global temperatures of 1°C was accompanied by a two-to threefold increase in the average prevalence of malaria in birds.
The most dramatic increases took place during the past 20 years.
Dr Garamszegi's work, published in Global Change Biology, found that the house sparrow (Passer domesticus) showed a malaria prevalence that was less than 10% before 1990 when worldwide temperatures were cooler, but in recent years nearly 30% were infected.
The great tit (Parus major) presented a similarly worrying increase, with less than 3% infected with malaria before 1995 but closer to 15% in recent studies.
The blackcap (Sylvia atricapilla), a migrant bird common in Europe that breeds in gardens, once had virtually no avian malaria but a study in 1999 showed nearly 4% had the disease.
The effects of warming on avian malaria were not universal.
Birds in Asia, North America and South America suffered much less change in their levels of infection during warm years than did birds dwelling in Africa and Europe.
Such trends may not have any relevance to the malaria parasites that infect humans.
But avian malaria is already ravaging the native birds of Hawaii and it is now wreaking havoc in New Zealand, says Dr Garamszegi.
Human beings may be able to mitigate the spread of malaria, but birds will need the help of conservationists if some species are to survive.