New Analysis Of Amazon Trees Shows They Will Survive Global Warming

Lawrence LeBlond for – Your Universe Online

Past studies on climate change´s effect on trees–notably those in the Amazon Rainforest–have suggested they will likely die out as a result of warming temperatures. However, a new genetic analysis has revealed this is not the case, finding that Amazon tree species would likely survive man-made climate change.

Researchers from the University of Michigan and University College London show through their research that some Amazonian tree species have survived previous periods as warm as many of the global warming scenarios forecast for the century´s end.

However, while Amazonian tree species will likely survive man-made climate warming trends, they remain susceptible to other factors that are sure to come in the wake of a warming planet. The study, published in the latest issue of Ecology and Evolution, suggests that extreme drought and forest fires will be the biggest threat to Amazonia forests as the temperatures rise.

Over-exploitation of the region´s resources will also threaten the future of the forest. While the trees will likely endure man-made warming trends, man himself is a much bigger threat–in the form of deforestation–to the fate of the forests. The authors recommend that a tough conservation policy should focus on preventing deforestation for agriculture and mining to preserve the Rainforest and reducing greenhouse gas emissions.

Interestingly enough, while man-made warming itself is not going to kill off Amazonian tree species, man is creating warming trends by felling these very same trees. Trees and other plants are important for the removal of planet-warming carbon dioxide from the atmosphere, and fewer trees mean an even warmer planet. By preserving the forests through conservation, man would be helping to keep the planet a little cooler.

A cool planet is vital for a sustainable life. Think of the Earth as a computer: a computer needs to remain relatively cool to operate efficiently. In personal computers, fans are used to keep the system cool. If the fan fails, the computer heats up and eventually gets too hot to run efficiently and crashes. But if other problems compromise the system, such as a virus, it doesn´t necessarily harm the fan. While the computer runs inefficiently, the fan continues to run as it normally should, but may burn out due to other issues that have affected the machine.

The same is being seen with trees in the Amazon.

“Our paper provides evidence that common Amazon tree species endured climates warmer than the present, implying that — in the absence of other major environmental changes — they could tolerate near-term future warming under climate change,” said lead author Christopher Dick, an associate professor of ecology and evolutionary biology and acting director of the UM Herbarium.

Study co-author Dr. Simon Lewis, of UCL Geography, said: “The past cannot be compared directly with the future. While tree species seem likely to tolerate higher air temperatures than today, the Amazon forest is being converted for agriculture and mining, and what remains is being degraded by logging, and increasingly fragmented by fields and roads.”

“Species will not move as freely in today’s Amazon as they did in previous warm periods, when there was no human influence,” added Lewis. “Similarly, today’s climate change is extremely fast, making comparisons with slower changes in the past difficult.”

“With a clearer understanding of the relative risks to the Amazon forest, we conclude that direct human impacts, such as forest clearance for agriculture or mining, should remain a focus of conservation policy,” Lewis said. “We also need more aggressive action to reduce greenhouse gas emissions in order to minimize the risk of drought and fire impacts to secure the future of most Amazon tree species.”

For the study, Dick and his colleagues used a molecular clock approach to determine the ages of 12 Amazon tree species (including balsa and kapok) most common throughout the region. Samples were collected in Panama, Ecuador, Brazil, Peru, French Guiana and Bolivia.

Once they had their samples, the team looked at climatic events that have occurred since those tree species emerged. In general, the researchers surmised that the older the age of the species, the warmer the climate it has previously survived.

Dick and his colleagues determined that nine of the species collected have been around for at least 2.6 million years, seven for at least 5.6 million years, and three of those have existed in the Amazon since 8 million years ago.

“These are surprisingly old ages,” Dick said. “Previous studies have suggested that a majority of Amazon tree species may have originated during the Quaternary Period, from 2.6 million years ago to the present.”

In its 2007 Third Assessment Report, the Intergovernmental Panel on Climate Change (IPCC) projected that the planet will warm to between 3.2 and 8.1 degrees Fahrenheit by the end of this century. The researchers said air temperatures across much of Amazonia during the Early Pleistocene Epoch (3.6 million to 5 million years ago) were similar to the lowest projections of about 3.2 F warmer for our future. In the Late Miocene Epoch (5.3 million to 11.5 million years ago) air temps were similar to the highest IPCC projections of 8.1 F by century´s end.

“The most lasting finding of our study may be the discovery of ancient geographic variation within widespread species, indicating that many rain forest tree species were widely distributed before the major uplift of the northern Andes,” said co-author Eldredge Bermingham of the Smithsonian Tropical Research Institute.

To determine the age of each tree species, the team extracted and sequenced DNA from plant samples, then looked at the number of genetic mutations contained in the sequences. Using the molecular clock approach, they were able to estimate how long it would take for each tree population to accumulate the observed number of mutations, providing a minimum age for each species.

“An important caveat is that because we’ve been in a cold period over the past 2 million years — basically the whole Quaternary Period — some of the trees’ adaptations to warmth tolerance may have been lost,” Dick said, adding that more research will be needed to “test whether this has occurred.”

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