Ancient Hunters Could Have Started Anthropocene Earlier than Initially Thought
30.06.2010 - Flora & Fauna, Human Dimension, Arctic
A new study, accepted for publication in the journal Geophysical Research Letters, suggests that massive mammoth die-off could have resulted in an early contribution to global warming. The study by Chris Doughty, Adam Wolf, and Chris Field - all at the Carnegie Institution for Science - offers a possible scenario to explain how hunters could have triggered climate warming thousands of years ago.
As mammoth populations plummeted, this made it possible for birch trees to dominate the grasslands, since mammoths grazed down birch trees, keeping the terrain an open grassland. However being darker, the birches could absorb more light, adding to natural warming. Then as mammoth survival became increasingly difficult, the birch trees were free to settle even further.
In order to find out how much an effect this process had on climate, the team examined ancient records of pollen from lake sediments in Alaska, Siberia, and the Yukon Territory. By looking at the impacts of modern-day elephants, the team was further able to determine that the fall of mammoths would have allowed birch trees to spread over several centuries and cover one-quarter of Siberia and Beringia—the ancient land bridge between Asia and Alaska.
Using a climate simulation, the team tried to find out whether the spread of birch trees could have warmed the whole planet more than 0.1°C over the course of several centuries. While a mere quarter of the birch tree spread would have been due to mammoth extinctions, this study suggests that ancient hunters could have contributed to global warming by finishing off the species. This means thee Anthropocene - the current period in the Earth's history when human activities have had a significant worldwide impact on the planet’s ecosystems – would have started several thousands of years earlier than initially thought.
