The authorities on the Brazilian stretch of the Amazon are taking emergency action to deal with one of the worst droughts in decades. Scientists say water levels in the river have fallen to a thirty-year low. This report from Simon Watts:

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When water levels fall, the biggest effect is on transport - ferries and barges are the only real way of moving goods and people around an area that spans about half the South American continent. In the last few weeks, the river and its tributaries have become increasingly difficult to navigate, and vital supplies of food, medicine and fuel are now struggling to get through. In an example of the risks, sixteen people were killed last Friday in a ferry accident which the captain blamed on difficult river conditions.

The dry weather in the Amazon has also caused huge fires in jungle areas. One recent blaze covered northern Bolivia in smoke, as well as the neighbouring part of Brazil. As to the cause of this low rainfall, scientists say it's probably cycles in the climate, not global warming. They think the weather in the Amazon is affected by sunspots and water temperatures in the Pacific - factors which vary in regular patterns. The bad news is that this dry cycle is expected to continue for another month.

Simon Watts, BBC, Americas Editor

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a lifeline
something which provides access to the necessary things in life

indigenous tribes
groups of people who were born and live in an area

tributaries
smaller rivers which run into a big river

vital
very important

blaze
another word for a very large fire

cycles in the climate
weather patterns which are repeated over years

factors which vary
things that change

this dry cycle
this period of dry weather