The world's population is due to exceed 7 billion this month and is forecast to rise to over 10 billion by 2050, putting a phenomenal strain on global resources, scientists say.
The Earth's natural resources like food, water and forests are already being depleted at an alarming rate, causing hunger, conflict, social unrest and species extinction, experts at a climate and health conference in London warned.
Increased hunger due to food yield changes will lead to malnutrition; water scarcity will deteriorate hygiene; pollution will weaken immune systems and displacement and social disorder due to conflicts over water and land will increase the spread of infectious diseases, they said.
By 2050, there could be 70 million additional deaths in sub-Saharan Africa alone, said Tony McMichael, professor of population health at the Australian National University.
As mosquito species spread due to climate change, the transmission rate of diseases like malaria will increase, engulfing countries like Zimbabwe from 2025 to 2050.
An extra 21 million people in China could be at risk from schistosomiasis as global warming increases floods, enabling disease-carrying water snails to travel to new areas.
Health risk central
"Climate change will progressively weaken the Earth's life support mechanism," McMichael said. "Health is not just collateral damage on the side; the risk is central and represents a denouement of all the other effects of climate change."
The effects of climate change will only exacerbate the problems, putting the health of ecosystems, animal species and humans in danger, the experts said.
Health effects will not just be felt in Africa or Asia – Europe will also feel the consequences.
"The problem of over-consumption in high income countries has produced an ecological and financial debt," Ian Roberts, professor at the London School of Hygiene and Tropical Medicine, told Reuters.
"The biggest risk to human health is from the rise in fossil fuel use, causing cardiovascular disease, stroke and cancer," he added.
Europe will also be at risk from heat waves, floods and more infectious diseases as pests shift to northern latitudes, said Sari Kovats, lead author of the Europe chapter for the Intergovernmental Panel on Climate Change's (IPCC) fifth assessment report.
"The fact is, there is more evidence that diseases are moving north," she said.
Other species also endangered
The IPCC's next report, which is due out in 2013-2014, will include chapters on human security and livelihoods and poverty for the first time to reflect the new raft of scientific evidence, she added.
Human health is not only at risk. Animal and plant species are also endangered.
"Many species are already facing a raft of pressures and climate change is creating a new range of additional problems," said Paul Pearce-Kelly, senior curator at London's Zoological Society.
Around 15% to 37% of over 6,000 species of amphibians are predicted to become extinct by 2100, he said.
In the Earth's history, there have been five mass extinctions, but there is now a 10,000-fold faster extinction rate than at any time on record.
"We are losing three species an hour, and this is before climate change is doing anything," said Hugh Montgomery, director at University College London's institute for human health and performance.
(Reuters Health, Nina Chestney, October 2011)