"With a clearer understanding of the relative risks to the Amazon forest, we conclude that direct human impacts such as forest clearances for agriculture or mining should remain a focus of conservation policy. We also need more aggressive action to reduce greenhouse gas emissions in order to minimise the risk of drought and fire impacts to secure the future of most Amazon tree species."
The 12 tree species used in the study are broadly representative of the Amazon tree flora. Samples were collected in Panama, Ecuador, Brazil, Peru, French Guiana and Bolivia.
To determine the age of each tree species researchers extracted and sequenced DNA, analysing the number of genetic mutations. Using a molecular clock approach and population genetic models they estimated how long it would take for each of the species to accumulate the observed number of mutations, providing a minimum age for each species. They determined that nine of the tree species had existed for at least 2.6 million years, seven for at least 5.6 million years, and three for more than 8 million years.
With reference to climatic events that have occurred since those tree species emerged, the authors inferred that the tree species had previously survived warmer climates. Air temperatures across Amazonia in the early Pliocene Epoch (3.6 million to 5 million years ago) were similar to Intergovernmental Panel on Climate Change (IPCC) mid-range projections for the region in 2100. Air temperatures in the late Miocene Epoch (5.3 to 11.5 million years ago) were about the same as IPCC projections for the region in 2100 using some of the highest carbon-emission scenarios.
|Contact: Ed Nash|
University College London