THE Amazon rainforest is enduring its most severe drought in half a century and the Brazilian Government has declared a state of emergency in the worst-affected area as falling river levels cut off communities from the wider world.

Many tributaries in the Amazon basin have dwindled to a trickle or dried up, the result of an exceptionally harsh dry season that some scientists believe may be linked to the violent hurricane season in the northern hemisphere that spawned Katrina, Rita and Stan.

Traditionally, droughts in the Amazon are linked to unusually warm surface water in the Pacific Ocean, a phenomenon known as El Niño. But some scientists have speculated that unusually warm water in the North Atlantic has caused more air to rise in that area, the reason for the destructive hurricane season this year.

Rising air in the northern Atlantic is in turn offset by descending air in the Amazon, which decreases the chances of rain. Carlos Nobre, a meteorologist with the Brazilian National Institute for Space Research, said: “This is still speculative, but it is physically consistent.”

Rainfall across the Amazon during July was only one third of average and in June and August only two thirds. River levels at the Peruvian jungle city of Iquitos are the lowest in 36 years. The Solimoes tributary on Brazil’s border with Colombia has dropped to 5ft, its lowest recorded level.

At 4,000 miles, the Amazon is the world’s second-longest river, after the Nile, but it carries far more water than any other river system. The Amazon basin is made up of a vast network of tributaries that drain water from Bolivia, Peru, Ecuador, Colombia and Venezuela into its main branches in Brazil. There it runs across the north of the country and empties into the Atlantic Ocean.

Many towns and villages in this sparsely populated rainforest region are reachable only via the rivers, which play the role of motorways. These can handle ocean-going vessels hundreds of miles inland.

As water levels have fallen, deliveries of food, medicine, fuel and other supplies have not been able to get through to inhabitants of these riverside communities, known as ribeirinhos, or river folk.

Drinking water is becoming scarce, leading to fears of outbreaks of diseases as people resort to using stagnant pools for drinking and washing. Medical supplies are also running low, and the authorities are worried about dwindling stocks of malaria and yellow fever treatments in mosquito-infested jungle towns.

The governor of Amazonas declared a state of emergency on Monday and has called for Brazilian army helicopters to fly supplies into cut-off communities. Soldiers will also be sent to dig wells in towns without drinking water.

Boats carrying fuel from the river port of Manaus to power generators in the capital of the neighbouring western Amazonian state of Rondônia had to turn back as their hulls were scraping along riverbeds. Now supplies are being brought by trucks via the far longer and more expensive southern land route.

Several communities have suspended their school year because no supplies have been able to get through. Fires set by farmers to clear land are reported to be burning out of control without rain to dampen them down.

Scientists say that the impact of the drought has been worsened by deforestation — a fifth of the original rainforest has been cut down in recent decades. Cleared areas release less moisture into the air and are less able to hold water in the ground when it does rain, causing excessive run-off.

The smoke from fires used to clear forest is also thought to inhibit rainfall. Smoke particles prevent the formation of large drops of water that fall as rain, instead forming smaller drops that rise with clouds until, at great height, they produce huge hailstones, a process that also causes intense thunderstorms. The hail melts in descent, causing downbursts rather than moderate rain — again aggravating run-off.

The Brazilian environmental protection agency says that the drought threatens long-term damage to the flora and fauna of the jungle. It says that severe drought kills Amazonian trees, making the ecosystem more vulnerable to fires.

Also threatened are rare aquatic species. The agency says that it has received reports of the deaths of more than 100 freshwater manatee — an endangered mammal unique to the Amazon that grows up to 10ft (3m) long and can weigh nearly half a tonne.

There are two species of Amazon dolphin and countless fish, including piranha, catfish, electric eels and stingrays. In rivers and pools throughout the region shoals have been trapped and killed by the receding waters. The capybara — a pig-sized amphibious rodent that lives on riverbanks — is also under threat as its diet, mainly of aquatic plants and grasses, disappears. Tapirs, which grow up to 600lb (270kg), share a similar diet and are also at risk. Predators, such as the jaguar, giant otters and wild dogs, suffer in turn.

But inhabitants of the Amazon hope that the dry spell will end soon. The rainy season should start by the end of the month.

LAND OF 50 MILLION SPECIES

The area was probably named after the mythological women warriors, the Amazons, after Spanish settlers fought fierce local women

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