Climate
will alter the soil that feeds us
One
of the main species of microbes that hold the soil together is likely
to be affected by rising temperatures, with unpredictable
consequences for fertility and erosion.
By Tim Radford
4
July, 2013
Global
warming may be about to
change the ground under our feet –
and perhaps not in a good way. It could be about to affect one of the
most important communities on the planet: the tiny microbes that make
life possible for the rest of creation, according to new research by
scientists in the US and Spain.
Cyanobacteria are
almost everywhere, have been around for the whole of life’s 3.5
billion-year history, and fix nitrogen from the atmosphere to
fertilise plants and feed animals.
They
are so common, and so numerous, that they form collectives that can
be picked up by hand, and be seen even from space. As
photosynthesisers, these blue-green algae also deliver the oxygen to
keep the animal world on the move.
Ferrari
Garcia-Pichel and colleagues report
in the journal Science that
they examined cyanobacteria in desert soils through the whole of
North America. They found that two species dominated. One,
calledMicroceleus
steenstrupii,
lives in the hot deserts while the other, M.
vaginatus,
prefers cold dry places.
But,
of course, the planet is becoming warmer with each decade. “By
using our data with current climate models, we can predict that in 50
years, the cyanobacterium that fares better in warm temperatures will
push the cold-loving one off our map,” said Professor
Garcia-Pichel.
“M.
steenstrupii could
completely dominate the crusts everywhere in our study area by then.
Unfortunately we don’t know much about this microbe or what will
happen to the ecosystem in the absence of M.
vaginatus.”
“This study tells us we can no longer neglect microbes in our considerations”
The
real hazard, for humans and other creatures that depend on
cyanobacteria – and that adds up to all life on Earth – is that
there is likely to be a knock-on effect on soil fertility, and soil
erosion: it is the “living crusts” formed by these microbes that
in many places hold the soil together, and sometimes researchers try
to combat cases of severe erosion by injecting these cyanobacteria
into the dust to act as soil stabilisers.
The
finding is ominous: but an omen of what? Once again, researchers have
unearthed – to use an appropriate metaphor – evidence of the
intricacy of the connections between air, water, rock, temperature,
life and climate.
But
this same discovery is a reminder of just how little science yet
knows about the microbiology of the world beneath our feet. Before
this research, nobody had expected cyanobacteria to have divided the
deserts into two separate kingdoms, with presumably two separate
ecologies.
“Our
study is relevant beyond desert ecology”, says Garcia-Pichel. “It
exemplifies that microbial distributions and the partitioning of
their habitats can be affected by global change, something we’ve
long known for plants and animals. This study tells us we can no
longer neglect microbes in our considerations.” – Climate
News Network
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