When you think of the remotest and wildest
places on Earth, aside from the polar regions, tropical rainforests are
likely to come to mind straight away. However, a paper that I have recently
read questions whether ‘virgin’ rainforest is actually as pure as we have
previously thought.
They argue that our three major rainforests
are actually secondary rainforests, and the areas have been deforested once
before. The forests investigated are the Amazon basin, the Indo-Malay basin and
the lower Congo basin. To test their hypothesis three geographers from the
University of Oxford collated many case studies of the areas. Their objective
was to look at evidence that humans have previously diminished the rainforests,
with the forests subsequently regaining their biodiversity up to its current
status.
An item of evidence put forward are the
presence of fertile “terra preta” soils as standard in rainforests today. The
formation of these soils is known as being due to prehistoric burning and
subsequent agricultural activity. Additionally there is plentiful
archaeological confirmation of substantial past settlements, which indicate
formation of intensive agricultural land and parkland. Included in this
evidence are stone tools, pottery fragments and palm oil nuts. Palaeoecological
findings also firmly support the terra preta soils’ burning hypothesis, because
distinct charcoal horizons are found.
Using this evidence it is thought that
these three rainforest regions (and possibly others) supported huge networks of
prehistoric humans who were actively changing the landscape around them,
followed by population crashes in the areas. The time at which these activities
were occurring varies between the regions, as illustrated in the figure above.
As this paper is based on a multitude of
studies and has many points of evidence, I believe it puts forward a good case
for our present day rainforests being secondary. This is an important
realisation, because it shows these areas are not as fragile as we once
thought, and are clearly well adapted for bouncing back providing enough forest
is left for that to be viable. Further palaeoecological work could now be done
to see the rate at which the rainforests recovered, and whether biodiversity is
as high as it was in the primary rainforests.
This may help to put into perspective just
how much of a risk to rainforests we humans are being presently. Could it be
that the depletion of natural resources that comes as the rainforests are being
chopped down, for example wood and medicinal plants, may not be as irreversible
as once thought?
