91Èȱ¬

Tree species in the Amazon rainforest are so many and varied that it would take three centuries to catalogue them, a major study has estimated.

In research published in the , more than 500,000 museum specimens dating back 300 years were audited.

They say nearly 12,000 tree species have been discovered so far.

Based on this figure, they predicted that about 4,000 rare types remained to be discovered and described.

The scientists say the species list will assist those trying to preserve the world's most bio-diverse rainforest.

"The checklist gives scientists a better sense of what's actually growing in the Amazon basin, and that helps conservation efforts," said one of the study's authors, Dr Hans ter Steege, from the Naturalis Biodiversity Centre in the Dutch city of Leiden.

The research was made possible by the digitisation of museum collection data worldwide.