Keeping Gondwana Alive

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					                          KEEPING GONDWANA ALIVE

M J de Wit1 and J M Anderson2
1
University of Cape Town, Rondebosch, South Africa
2
The National Botanical Institute, South Africa

This sample abstract is only intended to illustrate the format requested for abstracts
submitted to the 5th EGU Alexander von Humboldt International Conference. The
content below dates from 2001.
We take a holistic view of the changing Earth during the life span of the supercontinent
Gondwana, from its birth 550 million years ago to its final demise 500 millions years
later. We use this view to link major extinctions and global biodiversity changes that
have repeatedly occurred in the past to help understand the build-up to the explosive
extinction phase in progress today. Through 0.5 billion years, from the early Cambrian
biosphere "explosion" and the Silurian, when vascular plants first colonised the
landscape, to the Tertiary when mammals came to dominate the environment, plate
tectonics has very evidently and dramatically set a chain reaction of change in motion --
continental realignments and mountain building to climate and vegetational remodelling.
Unexpected surprises abound during rapid transitions, and hypothesis and fact mingle
richly in the fields of endogenous processes and asteroids. Little is proven, but just as
new ferment was provided by the theories of continental drift in the early 1900s and
plate tectonics in the 1960s, so has realisation that the Earth operates as a gigantic
interactive recycling machine that is episodically disturbed by asteroid impacts. Earth
Systems Science provides scope for new insight into evolutionary patterns and
biodiversity fluctuations.
Coupled Earth Systems modelling is a 1990s giant leap forward, fuelling fresh insight to
the repeated profound evolutionary metamorphosis in the floral and faunal world, as we
will demonstrate for the Permian-Triassic extinction event during Gondwana's "mid-life
crises", 251 million years ago when chaos suddenly set in. Today Homo sapiens sapiens
is rapidly emerging as our greatest “challenge” on this changing Earth. Uniquely, in the
episodic cycles of life's radiations and extinctions, has one species colonized globally,
exploded in numbers, and impacted on their environment so totally as to be the cause of
one of these global major extinctions - the Sixth. We are that species. From our DNA,
from linguistics, from anthropology and archaeology, we learn that all 6 billion of us are a
close family arising from a single female (“Mitochondrial Eve”) most probably at the
southern end of Africa around 140,000 years ago. For ~100,000 years we spread
through Africa as hunter-gatherers, effectively just one predator amongst many in
balance in the ecosystem. Estimates suggest our saturation population across Africa
would have been a mere 50,000 individuals. We spilled out of Africa ca 44,000 B.P. to
the corners of the earth, and since then our population, our cultural diversity, our
technology and our disastrous impact on the other 10-100 million species sharing our
space has exploded exponentially. Only in the last couple of decades have the words
biodiversity and the Sixth Extinction been coined and popularized, and only with these
new words have we become conscious that we are the cause of this Sixth Extinction and
that it is already well advanced and deepening. It is only we who can stem the
Extinction, and we have perhaps a decade to make the most decisive moves. This is the
purpose of the “Gondwana Alive” initiative.

				
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