posted on Jun, 21 2006 @ 10:31 AM
Originally posted by loam
Will someone show me a study, not a mere assertion, that says the Amazon was once grassland?
It was. Along with the boreal forests in the northern hemisphere.
It may have been rainforest during the ice age, maybe not. The study referenced above cautions about uncertainty, despite the title and brief
After the ice age the Amazon basin (but maybe not central Africa -- studies there are still inconclusive) reverted to savannah, and started
reforesting about 5000 years ago. After the ice retreated the boreal forest didn't exist, of course, and it had to reforest. There is some evidence
the Canadian shield was a temperate forest prior to the last ice age -- ponderosa pine stumps and tree boles have been found on Baffin Island. About
5000 years ago the Great Basin of the western U.S. was a prairie, not unlike the American midwest today. It was not a cold desert. the PJ
(pinyon-Juniper) forests that characterize the Great Basin today did not exist then, PJ was all south of the Colorado River. Much of the Sierra
Nevada and Cascades did not have significant forest cover until relatively recently. Surveys and analysis clearly show that despite the wild claims
of the environmental industry there is as much or more old growth now in the Sierra Nevada mountains as ever existed historically, and up to 3x as
much total forest biomass.
An interesting side discussion to global forest changes over time is Douglas-Fir -- the major timber tree of the NW U.S. Prior to the ice age it was
also the primary forest tree in northern Europe. Since Europe's mountain ranges run east-west and the North American are north-south, in Europe the
advancing glaciers 'pushed' the Douglas-fir into extinction. So is the planting of Douglas-Fir into the forests of Europe introducing an exotic
species or is it the re-introduction of a once widespread species?
That is a philosophical question that also impacts the rainforest debate. What time frame are you willing accept when discussing changes?