Climate change to disrupt soil nutrients

The increased aridity expected this century as a
result of climate change may disrupt the balance
of key soil nutrients with a knock-on effect on soil
fertility threatening livelihoods of more than two
billion people, a study finds.
The drop in nitrogen and carbon concentrations
that occurs as soils become dryer could have
serious effects on ecosystem services such as
food production, carbon storage and biodiversity,
according to the Nature paper published today.
Loss of nitrogen and carbon, which are the basic
building blocks of living organisms, drastically
affects land’s productivity, says Fernando T.
Maestre, a biologist and geologist from King Juan
Carlos University, Spain, and a co-author of the
report.
“If plant productivity is reduced, the capability of
the land to support livestock and crops will be
affected and this will have a big impact on people
who depend on them,” he tells SciDev.Net.
Drylands make up more than 40 per cent of the
world's land area, and host a similar proportion
of the world’s population. Many are expected to
get drier because of climate change.
“As global climate change progresses,
the ecosystem properties of many
drylands could pass a tipping point.”
David A. Wardle, Swedish University of
Agricultural Sciences
The study measured the nitrogen, carbon and
phosphorus content of soil at 224 sites across all
continents except Antarctica, which together
represent a wide range of soil and vegetation
types, climates and species diversity.
As ecosystems became more arid, it found, both
nitrogen and carbon concentrations decreased,
which may significantly impair plant and
microbial activity, with knock-on effects on
organic decomposition and plant growth.
Limited nitrogen content could also reduce plants’
ability to convert carbon dioxide into organic
compounds such as sugars through
photosynthesis, resulting in even greater climate
change, the study says.
Despite a rise in phosphorus levels, plants cannot
use this important element, as the enzyme they
need to absorb it through their roots is dependent
on nitrogen availability.
The study’s data suggest that “as global climate
change progresses, the ecosystem properties of
many drylands could pass a tipping point that will
be difficult or impossible to reverse,” writes David
A. Wardle, a researcher at the Swedish University
of Agricultural Sciences, in an accompanying
comment piece in Nature.
He adds: “Reduced soil carbon and nitrogen may
impair the supply of nutrients from the soil and
therefore the productivity of crops and livestock,
with potentially dire consequences for many of
the more than two billion people who inhabit
dryland regions.”