The Amazon rainforest lost trees and plants in a 2005 drought – shedding carbon equivalent to the weight of 140,000 Eiffel Towers or almost 200 Great Pyramids of Giza.

The drought, one of the worst in the past century, revealed the forest’s unexpected vulnerability to shifting rainfall and a huge role in releasing greenhouse gases – compounding problems such as logging and land clearance to create farmland.

The study in today’s edition of the journal Science (see story here) showed that the forest lost the equivalent of the annual carbon emissions of Europe and Japan during the drought — that’s five billion tonnes of carbon dioxide, or 1.4 billion tonnes of carbon stored in vegetation. The drought killed off some trees and slowed growth of other vegetation.

The Great Pyramid weighs perhaps 7.5 million tonnes, the Eiffel Tower 10,000.

The lead scientist of the study, Oliver Phillips of Leeds University, said that one answer could be for governments to consider even deeper cuts in their industrial emissions: the drought shows that people can’t rely on tropical forests to soak up emissions as the Amazon has been at least since the 1980s, a period of good growth ( … at least away from areas being burnt and chopped down).

So what can the world do? Among ideas: plant a tree in your back yard? Give tropical countries more incentives to safeguard the carbon stored in forests?

 (The picture top left, by Rickey Rogers, shows a small community of houseboats left stranded by receding waters near the city of Manaquiri, Amazonas State, in October 2005.)