'Little Ice Age' hastened fall of Aztecs, Incas
The vast empires of the Incas and Aztecs were highly advanced. They
kept detailed tax records, built elaborate temples, and at their height,
Central and South America boasted a thriving population of as many as 60
But their grand civilizations bore another trapping (feature) of
modernity, scientists have found one that until recently was thought
unique to our industrialised world: human-induced climate change.
In the 16th century, the diseases Europeans brought to the New World
decimated (destroyed) native peoples. With no natural defence against
smallpox, yellow fever, and a host of exotic new pathogens, 90 per cent
of the population was dead by 1600.
"We're talking about wiping out about nine per cent of the world's
population at the time," said Richard Nevle of Bellarmine College
Preparatory School, in San Jose, California.
Ruins of the old empire
According to Nevle and co-author Dennis Bird of Stanford University,
the killing left a lasting impact on the global climate. Suddenly as
much as 500,000 square kilometres (193,051 square miles) of cleared
farmland was no longer being tended, an area slightly larger than
California. And as the rainforest crept back in, it vacuumed carbon
dioxide out of the atmosphere in the process.
In all, the authors estimate that reforestation of South and Central
America could have removed up to 10 billion tons of carbon from the
Around the same time, climate records show from that global
temperatures cooled about 0.1 degrees Centigrade (about 0.2 degrees
Fahrenheit) from 1500 until 1750. But in northern Europe the dip was far
more dramatic, and came to be known as the Little Ice Age.
"You had advancing glaciers, frost and snow in places it had never
been seen before," Bird said. "When you have a couple of years of bad
weather, people take notice. But when you have 200 bad winters in a row,
that's something to write home about."
"You expect that after a pandemic like that, you're going to see a
recovery in land cover," said Jed Kaplan of Ecole Polytechnique Federale
de Lausanne (EPFL) in Switzerland, who was not involved in the study.
"We see a similar sort of reforestation following a real crash in
population after the Black Death, from 1350 to 1450."
CO2 levels didn't drop nearly as much after the Black Death, perhaps
three parts per million (ppm), compared to five to eight ppm following
the American pandemic.
Nevle and Bird admit that volcanic activity and a decrease in the
sun's intensity probably both played roles in triggering the Little Ice
Age. Still, Bird said, human activity was undeniably important.
"Humans have been altering the climate for longer than we ever
imagined," Bird said.
"We can use this as an analogy (comparison) to what we're dealing
with today [with global warming]," he added. "We are going to have to
have some drastic changes in our lifestyle, and they have to be
long-lived if we're going to get out of this mess we're currently in."