Despite net gains, humans’ treatment of nature significantly threatens health

Dr. Lee Jong-wook

9 December 2005 – 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 (WHO) 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.

Pressures on ecosystems could have unpredictable and potentially severe future impacts on health, the report states. Regions facing the greatest present-day risks, meanwhile, include sub-Saharan Africa, Central Asia, parts of Latin America, and certain areas in South and Southeast Asia.

Some of the most serious problems include:

  • Nutrition: Degradation of fisheries and agro-ecosystems are factors in the malnutrition of some 800 million people around the world. At least an additional billion people experience chronic micronutrient deficiency.
  • Safe Drinking-Water: Water-associated infectious diseases claim 3.2 million lives, approximately 6 per cent of all deaths globally. Over 1 billion people lack access to safe water supplies, while 2.6 billion lack adequate sanitation, and related problems of water scarcity are increasing, partly due to ecosystem depletion and contamination.
  • Solid Fuel Dependency: About 3 per cent of the global burden of disease has been attributed to indoor air pollution, a major cause of respiratory diseases. Most of the world's population uses solid fuels to cook and heat, a factor in deforestation.

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