Posts
Earth
has lost a third of arable land in past 40 years, scientists say
‘We
are reducing soils to their bare mineral components. We are creating
soils that aren’t fit for anything except for holding a plant up.’
By
Oliver Milman
2
December 2015
(The
Guardian) – The world has lost a third of its arable land due to
erosion or pollution in the past 40 years, with potentially
disastrous consequences as global demand for food soars, scientists
have warned.
New
research has calculated that nearly 33% of the world’s adequate or
high-quality food-producing land has been lost at a rate that far
outstrips the pace of natural processes to replace diminished soil
[Soil loss: an unfolding global disaster].
The
University of Sheffield’s Grantham Centre for Sustainable Futures,
which undertook the study by analysing various pieces of research
published over the past decade, said the loss was “catastrophic”
and the trend close to being irretrievable without major changes to
agricultural practices.
The
continual ploughing of fields, combined with heavy use of
fertilizers, has degraded soils across the world, the research found,
with erosion occurring at a pace of up to 100 times greater than the
rate of soil formation. It takes around 500 years for just 2.5cm of
topsoil to be created amid unimpeded ecological changes.
“You
think of the dust bowl of the 1930s in North America and then you
realise we are moving towards that situation if we don’t do
something,” said Duncan Cameron, professor of plant and soil
biology at the University of Sheffield.
“We
are increasing the rate of loss and we are reducing soils to their
bare mineral components,” he said. “We are creating soils that
aren’t fit for anything except for holding a plant up. The soils
are silting up river systems – if you look at the huge brown stain
in the ocean where the Amazon deposits soil, you realise how much we
are accelerating that process.
“We
aren’t quite at the tipping point yet, but we need to do something
about it. We are up against it if we are to reverse this decline.”
[more]
Yield
stagnation in cereals. This graph illustrates the yield trajectory
for several major cereal crops in the UK. Data from the World Bank.
Graphic: Grantham Centre
2
December 2015 (Grantham Centre) – Soil loss is an unfolding global
disaster that will have catastrophic effects on world food
production, scientists at the United Nations Conference on Climate
Change have warned.
Speaking
today (2 December 2015) at the 21st Conference of the Parties in
Paris, experts from the University of Sheffield’s Grantham Centre
for Sustainable Futures revealed that nearly 33 per cent of the
world’s arable land has been lost to erosion or pollution in the
last 40 years and vital action must now be taken to prevent the
devastating knock-on effects.
In
a new report, the Sheffield scientists urge that a sustainable model
for intensive agriculture is crucial to cope with the increase in
global food production needed to feed the world’s growing
population.
Meeting
this demand will become increasingly difficult as we feel the
intensifying effects of climate change.
At
the moment, intensive agriculture is unsustainable – under the
intensive farming system current crop yields are maintained through
the heavy use of fertilizers, which require high energy inputs to
supply inorganic nitrogen via the industrial Haber-Bosch process.
This consumes five per cent of the world’s natural gas production
and two per cent of the world’s annual energy supply.
However,
scientists have discovered that the key to creating a future
sustainable model for intensive agriculture could lie in the past and
even be supplemented by human excrement as an organic fertiliser.
Duncan
Cameron, Professor of Plant and Soil Biology at the University of
Sheffield, said: “Soil is lost rapidly but replaced over millennia
and this represents one of the greatest global threats for
agriculture.
“Erosion
rates from ploughed fields average 10-100 times greater than rates of
soil formation and nearly 33 per cent of the world’s arable land
has been lost to erosion or pollution in the last 40 years.
“This
is catastrophic when you think that it takes about 500 years to form
2.5 cm of topsoil under normal agricultural conditions. A sustainable
model for intensive agriculture could combine the lessons of history
with the benefits of modern biotechnology.”
Colin
Osborne, Professor of Plant Biology at the University of Sheffield
and Associate Director of the Grantham Centre for Sustainable
Futures, added: “Historically, good soil management was
supplemented by the collection and application of ‘night soil’,
which is human excrement – a practice that continued into the 20th
century.
“In
a historical example of the circular economy, this closed the
nutrient loop, recycling organic nitrogen and phosphorus back into
soil.
“A
sustainable soil-centric reengineering of the agricultural system
would reduce the need for fertiliser inputs and pesticide
application, and require less irrigation, thus contributing towards
safeguarding finite natural resources.”
Professor
Cameron and his team believe that a sustainable model for intensive
agriculture is founded on three principles:
Managing
soil by direct manure application, rotating annual and cover crops,
and practising no-till agriculture (not cultivating and preparing the
land). These practices connected to ‘conservation agriculture’
restore soil organic matter, structure, water-holding capacity and
nutrients, averting soil loss while benefiting crops.
Using
biotechnology to wean crops off the artificial world we have created
for them, enabling plants to initiate and sustain symbioses (close
interactions) with soil microbes. These symbioses allow crops to
exploit microbial biology to tap into soil organic nutrient reserves,
and prime plants to better defend themselves against pests and
diseases.
Recycling
nutrients from sewage in a modern example of the circular economy.
Inorganic fertilizers could be manufactured from human sewage in
biorefineries operating at industrial or local scales. A number of
technical challenges impede the immediate adoption of this idea, but
these can readily be addressed through research.
Professor
Peter Horton, Emeritus Professor of Biochemistry and Associate
Director of the Grantham Centre, said: “In order to facilitate such
a wholesale redesign of the agricultural system, we need to assess
the potential scientific, economic, cultural and political
impediments to this happening, and resolve the potential benefits of
this redesign for sustainability.
“In
doing so, we could reduce our dependence on energy-intensive and
non-renewable inorganic fertiliser, reduce fertiliser pollution of
watercourses, and create a soil fit for future generations.
“Of
course, no one model equally fits all problems; different
agricultural scenarios such as varying geography, climate or crop
might benefit from our approach more than others and any redesign of
the agricultural system needs to be sufficiently flexible to
accommodate this.”
No comments:
Post a Comment
Note: only a member of this blog may post a comment.