For every 1% rise in deforestation there is an 8% rise in malaria mosquitos. Credit: © GettyImages

Destruction of the Amazon rainforest is opening the door to malaria-bearing mosquitoes, researchers are warning. They hope to highlight how environmental damage is fuelling human disease.

The team collected 15,000 mosquitoes swarming around a jungle road in northeast Peru - and counted how many of these were Anopheles darlingi, the local species that pumps the malarial parasite into human veins. Using satellite images, they tallied these figures with the level of deforestation caused by farming and villages.

Every 1% increase in deforestation boosts the number of A. darlingi by 8%, conclude Jonathan Patz of Johns Hopkins University in Baltimore, Maryland, and his team. A. darlingi may come to dominate other species because it thrives in open, sunlit ponds, Patz suggests.

The finding might inform forest managers, Patz hopes. In this study, for example, the insects ran wild once 30-40% of forest was destroyed. "Our goal is to prevent [disease] as far upstream as possible," he says.

Malaria expert Phil Lounibos of the University of Florida in Vero Beach agrees that deforestation might boost A. darlingi swarms. But the species first surged in the 1990s after the introduction of tropical fish farms, he points out: "The whole problem wouldn't be so acute if this species wasn't imported."

Field study

Patz is part of a burgeoning group of scientists studying the impact of environmental damage on the health of animals and humans. Dubbed 'conservation medicine', the field ranges from the impacts of pollution on cancer to the contribution of global warming to amphibians' global demise.

Conservation medicine has gained new recognition after the recent outbreaks of West Nile virus and severe acute respiratory syndrome (SARS) - diseases that crossed into humans partly because of our changing contact with animals. These events "drive home the message", says Peter Daszak, head of the Consortium for Conservation Medicine, part the Wildlife Trust, a charity based in Palisades, New York.

The consortium of five academic institutions - including Johns Hopkins University - is pushing for more studies to inform conservation policy decisions. Daszak himself is investigating whether urbanization or farming has cut the diversity of birds and hence fuelled the spread of West Nile virus from birds to humans.

Daszak and Patz are awaiting the 2005 release of a major report from the Millennium Ecosystem Assessment, convened by the United Nations. This group of scientists is piecing together a picture of changing ecosystems and their impacts on human health to inform policy-makers.

Meanwhile, a smaller milestone will come in March 2004 with the launch of the field's own journal, EcoHealth, as well as an online forum for researchers called ecohealth.net. "Everything we look at is common-sense," sums up Daszak, "but it's so massively overlooked it's unbelievable."