Rise in Fires Began 10,000 Years Ago
8/19/98
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Title: Rise in Fires Began 10,000 Years Ago
Source: United Press International
Status: Copyrighted, contact source to reprint
Date: 8/19/98
WASHINGTON, Aug. 19 (UPI) -- In a million-year survey of fires on
Earth, researchers have documented a dramatic rise in conflagrations
beginning 10,000 years ago in sub-Saharan Africa.
Michael Bird and J.A. Cali of the Australian National University in
Canberra say the incidence of fire in sub-Saharan Africa began rising
about 400,000 years ago. But, writing in Thursday's issue of the British
journal Nature, they report evidence that the incidence of fires didn't
really rise dramatically until sometime around 10,000 years ago, or
later.
The fires caused changes in vegetation patterns and produced carbon
dioxide emissions that apparently were the cause of global climate
alterations from interglacial to glacial modes, the scientists said.
The fact that the most dramatic increase in fires began 10,000 years
ago or less ``suggests human activity, and that humans have exercised
significant control over fire regimes in sub-Saharan Africa for at least
the past few thousand years.''
Fire affects vegetation patterns, climate, and plays a central role
in modern ecosystems, they said.
Bird and Cali said they studied a million-year record of elemental
carbon, produced by biomass burning, that was buried in sea-floor
sediment on the Sierra Leone Rise in the Atlantic, which is downwind of
sub-Saharan Africa.
Vegetative burning accounts for about one third of annual man-made
carbon dioxide emissions, the scientists said, and there's ample
evidence these emissions can and do affect climate.
``Combustion has underpinned the technological ascent of the genus
Homo and lies at the core of current concerns over global change, both
through biomass burning and combustion associated with the production of
energy,'' Bird said.
``The potency of fire as an agent of environmental change has led to
speculation that prehistoric humanity may have been actively engaged in
modifying vegetation patterns, regional climate and atmospheric trace-
gas concentrations since long before the advent of modern concerns over
global change.''
In short, the man-made activity that experts say is causing global
warming now may actually be an ancient phenomenon, the scientists
surmised.
They said they used deep-sea sediments because such material
preserves ``undisturbed'' records of large-scale burning activity.
The sediment offers tantalizing clues about the distant past, they
said. For instance, low fire incidence implies wet conditions. But with
the expansion of savannahs in drier conditions, Bird said, fire
incidence increased, as did the proportion of grasses emitting gases
into the atmosphere.
They said this research clearly shows that ``a range of human
activities in sub-Saharan Africa may have resulted in regional
modifications to 'natural' vegetation patterns and climate.''