One-fifth of global farm soil degraded by salt
by Carol Smith
Salt is degrading one-fifth of the world's irrigated land and causing
around US$27.3 billion per year in economic losses, according to a new
assessment from the United Nations University (UNU). That's because
every day for the past 20 years, an average of 2,000 hectares of
farmland has been impacted by salt accumulation in arid and semi-arid
regions across 75 countries. Now these lands currently cover about 62
million hectares - equal to the size of France.
Salt-induced land degradation occurs in regions where rainfall is too
low to maintain regular percolation of rainwater through the soil and
where irrigation is practiced without a natural or artificial drainage
system. Irrigation that doesn't include drainage management causes salts
to stay behind in the root zone after the water has evaporated,
affecting soil properties and reducing productivity.
What with all the other agricultural and food security challenges of
today, this is a concerning trend. Which is why the UNU Institute for
Water, Environment and Health (UNU-INWEH) has published a new study
entitled The Economics of Salt-induced Land Degradation and Restoration
authored by eight experts based in Canada, Jordan, Pakistan and Sri
Lanka.
"To feed the world's anticipated nine billion people by 2050, and
with little new productive land available, it's a case of all lands
needed on deck," says principal author Manzoor Qadir, Assistant Director
of the Water and Human Development programme at UNU-INWEH. "We can't
afford not to restore the productivity of salt-affected lands."
Indeed, UNU-INWEH Director Zafar Adeel notes that the UN Food and
Agriculture Organization projects that we need to produce 70 percent
more food by 2050, including a 50 percent rise in annual cereal
production to about 3 billion tonnes.
"Each week the world loses an area larger than Manhattan to salt
degradation. A large portion of the affected areas in developing
countries have seen investments made in irrigation and drainage but the
infrastructure is not properly maintained or managed. Efforts to restore
those lands to full productivity are essential as world population and
food needs grow, especially in the developing world."
Big costs
Published in the UN Sustainable Development journal Natural Resources
Forum, the paper details crop productivity losses at farm, regional, and
global scales, the cost of doing nothing and the net economic benefit of
preventing and/or reversing land degradation.
The study estimates that the inflation-adjusted cost of salt-induced
land degradation in 2013 was US$441 per hectare, which puts global
economic losses at US$27.3 billion per year. The estimated cost of crop
losses was drawn from a review of more than 20 studies over the last 20
years in Australia, India, Pakistan, Spain, Central Asia and the United
States.
Well known salt-degraded land areas include:
Aral Sea Basin, Central Asia
Indo-Gangetic Basin, India
Indus Basin, Pakistan
Yellow River Basin, China
Euphrates Basin, Syria and Iraq
Murray-Darling Basin, Australia, and
San Joaquin Valley, United States
The paper presents selected case studies that highlight the potential
for economic and environmental benefits of 'action' to remediate
salt-affected lands compared to taking 'no action'.
In India's Indo-Gangetic Basin, crop yield losses for wheat, rice,
sugarcane and cotton grown on salt-affected lands could be 40 percent,
45 percent, 48 percent and 63 percent respectively. Employment losses
could be 50-80 man-days per hectare, with an estimated 20-40 percent
increase in human health problems and 15-50 percent increase in animal
health problems.
In the Indus Basin in Pakistan, wheat grain yield losses from
salt-affected lands ranged from 20-43 percent with an overall average
loss of 32 percent. For rice, the crop yield losses from salt-affected
lands ranged from 36-69 percent with an overall average loss of 48
percent.
Even in the US's Colorado River Basin, studies show the annual
economic impact of salt-induced land degradation in irrigated areas at
US$750 million.
"It is important to note that the above numbers on global cost of
salt-induced land degradation refer to economic losses based on crop
yield losses only," the paper says.
"These costs are expected to be even higher when other cost
components such as infrastructure deterioration (including roads,
railways, and buildings), losses in property values of farms with
degraded land and the social cost of farm businesses are taken into
consideration. In addition, there could be additional environmental
costs associated with salt-affected degraded lands as these lands emit
more greenhouse gases, thus contributing to global warming."
Salt-induced land degradation may also affect the business sector
negatively either directly or indirectly, targeting their inputs,
outputs, or processes.
The businesses in close connection with natural resources may be
affected, such as those dealing with basic resources (forestry, wood,
pulp, and paper), food and beverage, construction and materials,
industrial goods and services (transportation and packaging), utilities
(water and electricity), personal and household goods (clothing,
footwear, and furniture), leisure and travel (hotels and restaurants),
and real estate.
Therefore, reversing salt-induced land degradation would help these
sectors achieve potential economic gains by providing needed levels of
materials and services.
Reversing the trend
Although there are investment costs to preventing and reversing land
degradation, or to restoring degraded land into productive land, these
costs are much less than the costs of allowing land degradation to
continue and intensify.
But investing in effective remediation of salt-affected lands should
be part of a broader strategy for food security that would be defined in
national action plans, the authors argue. This approach would ensure
that barriers to the adoption of sustainable land management, including
perverse subsidies, are identified and removed.
Pertinent policies, well-designed salinity management plans,
supportive institutions, skilled human resources, provision of
facilities and infrastructure for disposal of salts, capacity
development of farmers, utilization of locally available resources and
the indigenous knowledge of local communities are crucial in combating
salt-induced land degradation.
While reversing salt-induced land degradation would obviously take
several years, the authors say that interim salinity management
strategies could set the course for effective remediation while
showcasing the importance of reversing land degradation and illustrating
the rewards of investing in sustainable land management.
- Our World
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