Opinion It's generally assumed that it would mean a disaster for the planet if the rainforests of the Amazon were to be replaced with farmland. But it turns out that, actually, much of the area was indeed farmland just a few thousand years ago.
We learn this from new research just published in the august Proceedings of the National Academy of Sciences. A team of mainly British-based scientists carried it out, seeking to explain the presence of various large human-dug ditches and earthworks criss-crossing today's thick Amazon jungles - and pre-dating them.
Some in the paleo-boffinry community suggest that the ditches mean that the pre-Columbian civilisations of South America had slashed and burned the immemorial rainforests to create large intensively farmed areas home to dense populations. Others contend that actually the jungles remained largely intact, with just a few incursions by small communities of people.
Neither of these scenarios are true, apparently.
"We went to Bolivia hoping to find evidence of the kinds of crops being grown by ancient Amerindian groups, and to try to find how much impact they had on the ancient forest," explains Dr John Carson of Reading uni. "What we found was that they were having virtually no effect on the forest, in terms of past deforestation, because it didn't exist there until much later."
Carson goes on to say:
"The scale of the earthworks that were built on these sites suggests that the land was capable of supporting relatively large populations. Our analysis shows that they were growing maize and other food crops. They also likely caught fish, and there's evidence from other parts of the Bolivian Amazon for people farming Muscovy ducks and Amazonian river turtles.
"Our findings have serious implications for understanding past climate change, and how the Amazon basin might react to more modern forest clearance."
Carson cautions that the idea - advanced by some, since the earthworks have become known - that the rainforests will simply return naturally following modern deforestation is not supported by his new findings. The primitive Amazonians didn't deforest the area, so the fact that jungle spread across their farms from around the period 0-300AD - probably due to the climate getting wetter - doesn't mean that today's deforestations are easily reversible.
But the new research does rather conclusively cast doubt on the alternative notion, that the Amazon rainforests are an immutable necessity for a reasonable world climate. Plainly there have been times even just within recorded human history when large chunks of the current jungle simply weren't there, and the land was used for farms instead - without any associated eco-disaster.
Carson and his colleagues' research can be read by PNAS subscribers here. ®