The Woolly Mammoth at the Royal BC Museum, Victoria, British Columbia.
Credit: Wikimedia
WASHINGTON DC: Even as far back as 15,000 years, humans may have had a hand in global warming, scientists suggest. Ancient hunters may have hastened the extinction of mammoths, which used to thrive in Siberia and North America.
According to a new study in the American Geophysical Union (AGU), the resulting change in vegetation may have contributed to heating by as much as 0.1 degrees Celsius (or 0.18 degrees Fahrenheit), which doesn't seem like much, but it could've had a huge impact.
"By showing that the disappearance of the mammoths probably impacted climate, we get to an interesting if-then situation. If humans contributed to the disappearance of the mammoth, they impacted the climate in doing that," said a researcher on the study, Chris Field of the Carnegie Institution for Science in Stanford, California.
Mammoths make way for birch tree explosion
Like modern elephants, mammoths had the propensity to knock down (and graze on) trees, particularly the birch trees that might have proliferated in the area that, before mammoth extinction, remained a grassland.
But as numbers of mammoths died off, birch trees spread, changing the face of the landscape.
The trees, which were darker than the grasses, absorbed more heat from the Sun, which heated up the atmosphere.
"Grasslands at high latitudes lead to cooling while forests lead to warming," said Adam Wolf, another researcher on the study also of the Carnegie Institution of Science.
Heat linked to mammoth decline
A warmer world made it harder for mammoths to adapt, which pushed them further toward extinction as the birch trees kept spreading.
The team of scientists looked at ancient birch pollen preserved in lake sediments from Siberia, Alaska, and the Yukon Territory, and found a spike in the amount of it about 15,000 years ago, around the time mammoth populations began a sharp decline.
