With 60 per cent of nature's gifts that support life on Earth, such as fresh water, clean air and relatively stable climate, being degraded or used unsustainably, the harm to human health, despite net gains, is already being felt and could worsen significantly over the next 50 years, according to a United Nations report released today.

“Over the past 50 years, humans have changed natural ecosystems more rapidly and extensively than in any comparable period in human history,” UN World Health Organization (http://www.who.int/mediacentre/news/releases/2005/pr67/en/index.html) Director-General Lee Jong-wook said of the agency report, Ecosystems and Human Well-being: Health Synthesis, which describes the complex links between the preservation of healthy and biodiverse natural ecosystems and human health.

“This transformation of the planet has contributed to substantial net gains in health, well-being and economic development. But not all regions and groups of people have benefited equally from this process.”

WHO’s lead expert on the report, Carlos Corvalan, said the benefits should be acknowledged. “But these benefits are not enjoyed equally. And the risks we face now from ecosystem degradation, particularly among poor populations directly dependent on natural ecosystems for many basic needs, have to be addressed,” he warned. Ecosystems are absolutely vital to preventing disease the report stresses. Many important human diseases have originated in animals, and so changes in the habitats of animals that are disease vectors or reservoirs may affect human health, sometimes positively and sometimes negatively. For example, the Nipah virus is believed to have emerged after forest clearance fires in Indonesia drove carrier bats to neighbouring Malaysia, where the virus infected intensively-farmed pigs, and then crossed to humans. Intensive livestock production, while providing benefits to health in terms of improved nutrition, has also created environments favourable to the emergence of diseases. Greater human contact with wild species and ‘bush meat’ from encroachment in forests and changes in diet also create opportunities for disease transmission. Trends ranging from forest clearance to climate-induced habitat changes also appear to have impacted certain populations of mosquitoes, ticks and midges, altering transmission patterns for diseases like malaria and lyme disease.