WASHINGTON: Tree-munching beetles, malaria-carrying mosquitoes and deer ticks that spread Lyme disease are three living signs that climate change is likely to exact a heavy toll on human health.

These pests and others are expanding their ranges in a warming world, which means people who never had to worry about them will have to start. And they are hardly the only health threats from global warming.

The Lancet medical journal declared in a May 16 commentary: "Climate change is the biggest global health threat of the 21st century."