The death of mangrove forests stretched over 1000 kilometres of Australia's northern coast a year ago has been blamed on extreme conditions including record temperatures.

About 7400 hectares of mangroves strung along the Gulf of Carpentaria died in a single month in early 2016 because of the unusual warmth, a prolonged drought and an El Nino that reduced local sea levels by about 20 centimetres, said Norman Duke, head of the Mangrove Research hub at James Cook University.

"Essentially, they died of thirst," Dr Duke said, adding that the sea-level drop triggered a "highly significant loss of tidal waters".

El Nino events are marked by a stalling or reversal of the easterly equatorial winds that would typically build up waters in the western Pacific. Still, previous El Ninos had not produced the huge death rate of mangroves as seen last year.