Latimer,
The claim about the Rio Negro comes from the National Institute of Space Research (INPE) in Brasil – see
http://www.ens-newswire.com/ens/oct2005/2005-10-24-05.asp
Feel free to take it up with them if you don’t believe them.
Peter,
Deforestation probably played a part, the main driver appears to have been increased ocean temperatures.
hunter,
Where did I say the drought is the worst ever?