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GAIA lives鈥攐r at least she appears to have been fighting fit 55 million
years ago. The argument that Earth鈥檚 organisms regulate the global environment,
and possibly even damp down global warming, received a boost this week.

Global temperatures soared around 55 million years ago when volcanoes pumped
huge amounts of the greenhouse gas carbon dioxide into the atmosphere. But
according to Santo Bains of the University of Oxford, huge growths of plankton
formed in the oceans shortly afterwards and absorbed so much atmospheric
CO₂ that temperatures returned to normal within 60 000 years.

Bains鈥檚 evidence for a huge plankton bloom is a big increase in the amount of
barium sulphate in ocean sediments laid down at that time in the North Atlantic
and off Antarctica. Living organisms are the main source of barium sulphate, and
modern studies show a strong link between the amount of barium sulphate and
organic carbon falling to the ocean bed as plankton die.

As the atmospheric CO₂ levels rose, temperatures initially climbed
by 6 掳C over 30 000 years. The combination of these rising temperatures,
extra rainfall washing nutrients into the oceans and the fertilising effect of
the CO₂ may have triggered a vast bloom of phytoplankton, according to
Bains. 鈥淎dvocates of the Gaia hypothesis might view this as one of the strongest
supporting pieces of evidence yet,鈥� he says.

Marine geologist Birger Schmitz of the University of Gothenberg in Sweden has
found similar barium sulphate peaks in Middle Eastern sediments from the same
period. Schmitz points out that these results contradict the predictions of
climate models, which suggest that the oceans should become less productive
under greenhouse conditions. 鈥淗ere the exact opposite happens,鈥� he says. 鈥淚t
shows the biosphere successfully regulating the climate as it goes to the
别虫迟谤别尘别.鈥�

The release of CO₂ from volcanoes mimics fossil fuel burning today.
But Bains points out that we would have to wait 60 000 years for plankton to
counteract current global warming.