Swells rise into a rice field in Dhal Char, Bangladesh, making it hard
to cultivate. Climate change may make such events more frequent and
severe.
Climate change is predicted to cause more intense and
frequent floods and droughts in Southeast Asia, threatening the world's
rice bowl and millions of people who live there unless preventive
actions are taken soon, scientists warn.
At the Climate
Smart Agriculture in Asia workshop held in Bangkok, Thailand, last
month, climatologists and agricultural researchers discussed farming
practices and technologies that could help the region cope with global
warming's effects, including rising temperatures, increased salinity,
and sporadic rainfall.
The conference was about "bringing all
these players together to look at how the research agenda needs to
change in the agricultural research world in relation to climate
change," said Bruce Campbell of the Consultative Group on International
Agricultural Research (CGIAR), which helped organize the two-day
workshop.
In addition, scientists at the meeting discussed
potential ways to use agriculture to mitigate the effects of climate
change by reducing greenhouse gas emissions such as methane.
Agriculture, forestry, and changes in land use account for a third of
greenhouse gas emissions, said Campbell, who is the program director of
CGIAR's Research Program on Climate Change, Agriculture and Food
Security (CCAFS).
"That's a significant portion," Campbell said, "but we can reduce it."
Breaking the Breadbasket?
The countries of
South and Southeast Asia are home to more than 30 percent of the world's
population, about half of whom depend on agriculture—mainly rice, but
also other crops such as wheat—for their livelihoods. But according to
the World Bank, global warming could reduce agricultural productivity in
the region by 10 to 50 percent in the next 30 years.
Some changes are apparent already. For instance, steadily rising sea levels have already led to an increase in the salinity of the water in Vietnam's Mekong Delta, where the Mekong River empties into the South China Sea. This has forced some people in the region to abandon rice production and shift to shrimp farming.
"In a way, they're prospering from the
change because they make more money raising shrimp than from rice," said
Matthew McCartney, a hydrologist with the CGIAR International Water
Management Institute, who attended the workshop. "But not everybody has
the capability to do that. Some people are adapting, but others are
losing out as a consequence of sea level rise."
According to the
United Nations Food and Agriculture Organization (FAO), rising sea
levels will increase salinity in the soils of rice-growing areas in
deltas and flood plains of other major rivers in Asia, including the Ganges, the Yangtze, and the Yellow Rivers.
In
the long term, such changes could force Asian countries to shift their
rice farms to other locations, similar to how some wineries in Australia
have moved to lower—and cooler—areas to counter the harmful effects of
global warming on their grapes.
"In Asia, there's the possibility
that you're really going to have to think more about radical
transformations in order to adapt, as the shift from rice to shrimp
illustrates," Campbell said.
Recharging Aquifers
But in other circumstances
adaptation can be incremental, and require only a gradual shifting of
farming systems. One such solution discussed at the Bangkok workshop was
using Managed Aquifer Recharge (MAR) technology in the region. MAR
involves using land in upstream areas of major rivers to capture and
store floodwater in natural underground aquifers, and then pump it out
during dry spells for farmers to use.
"The idea is to set aside
land where you know the soil conditions and geology will allow water to
infiltrate very quickly into the ground and pump it out later for
irrigation," McCartney explained.
MAR has been used for water
storage in arid areas such as Australia and Southern Europe, but not in
relatively wet regions that get regular rainfall such as Southeast Asia,
he added.
But the use of MAR in the region makes sense, because it could simultaneously solve two major problems that scientists foresee affecting the region. First, it would create a backup source of water that farmers could draw from in times of drought. It could also lessen damage from floods by diverting water from swollen rivers.
"In
Thailand, it could have had a major impact in reducing the flooding
[last year] in Bangkok," McCartney said. The floods caused $40 billion
in damage.
Early calculations indicate that about 40 square miles
(100 square kilometers) of recharge basins could irrigate more than 770
square miles (2,000 square kilometers) of farmland. Rather than
establishing one large recharge basin, the idea is to create lots of
smaller basins in suitable locations across the landscape.
"You
could quite easily make up the loss of production in the land that
you've set aside for the recharge basin," McCartney said.
Juliet
Christian-Smith, a senior researcher at the Pacific Institute in
Oakland, California, agreed that groundwater storage technologies such
as MAR could provide useful buffers against the increased variability in
rainfall that climate models predict.
"There are a lot of
positives associated with storing water underground," Christian-Smith
said. "We usually think of our water supply as coming from surface water
such as snowmelt and rivers, but in fact . . . much of the water that
supports irrigation and our global food supply comes from groundwater
and in many cases it is being depleted faster than it is being
recharged, leaving room for underground storage."
Because it
stores water underground, MAR isn't vulnerable to some of the problems
that plague dams, she added. For example, climate simulations predict
that many parts of the Earth will experience warmer temperatures, which
will in turn increase evaporation rates at dams. "There's also problems
with sedimentation, because if you have more flooding, you could have
more subsidence and erosion," she said. "That means your dam life and
the amount of water it can store is reduced."
CGIAR's McCartney
said MAR use in Southeast Asia is still only at the idea stage. "It
hasn't gone beyond people thinking about it," he said. "There would need
to be quite a lot more research done."
One question that will
need to be resolved, Christian-Smith said, is what impact recharge has
on water quality. A recent study in Bangladesh, for example, indicates
that repeated injection of water into underground aquifers could leach
arsenic and other toxic chemicals from the ground and concentrate it in
the water supply.
A Novel Solution for Water and Climate
Attendees
at the Bangkok workshop also discussed ways to help farmers not only
deal with climate change locally, but actually lessen its global impact
by reducing the amount of greenhouse gases their crops produce.
One
promising technology for doing this is called rice alternative wetting
and drying. As the name implies, it involves alternately flooding and
drying rice fields to reduce the amount of methane produced. Normally,
farmers leave their rice fields submerged for the entire growing season,
but this generates methane, a potent greenhouse gas. By drying the
fields periodically, scientists at the International Rice Research
Institute have shown that water consumption could be slashed by 30
percent and greenhouse gas emissions reduced by 25 to 50 percent,
without reducing yields.
"This is a fantastic technology for water
savings and greenhouse gas emission savings," Campbell said. "Rice is
so important across the whole of Asia that if one could implement this
technology in many different places, you could have significant
reduction in methane production."
But as with MAR, the details of
this technology will have to be worked out before it can be widely
implemented. For example, Campbell said, farmers must put much more
effort into water management; at the moment there are no incentives to
encourage them to do so. In other cases, large numbers of farmers would
have to coordinate their flooding and drying cycles for it to be most
effective.
Long-Term Management
While
promising technologies, neither MAR nor rice drying will be enough to
resolve all of the agricultural problems that scientists predict will
accompany climate change, experts say.
"To mitigate negative
effects of climate-induced floods and drought require the application of
integrated management concepts that have been developed in the past
years and are now increasingly applied," said Wolfgang Grabs, a
hydrologist with the United Nations World Meteorological Organization, a
co-sponsor of the Bangkok workshop.
"These include both
structural and non-structural methods," Grabs said, "such as dykes and
levees, land use planning, storage facilities for water, improved
forecasting and management of water resources, as well as suitable
climate change adaptation approaches."
CGIAR's Campbell agreed. "I
don't think there's going to be a silver bullet," he said. "You're
going to have to do many different things."
A Novel Solution for Water and Climate
Attendees
at the Bangkok workshop also discussed ways to help farmers not only
deal with climate change locally, but actually lessen its global impact
by reducing the amount of greenhouse gases their crops produce.
One
promising technology for doing this is called rice alternative wetting
and drying. As the name implies, it involves alternately flooding and
drying rice fields to reduce the amount of methane produced. Normally,
farmers leave their rice fields submerged for the entire growing season,
but this generates methane, a potent greenhouse gas. By drying the
fields periodically, scientists at the International Rice Research
Institute have shown that water consumption could be slashed by 30
percent and greenhouse gas emissions reduced by 25 to 50 percent,
without reducing yields.
"This is a fantastic technology for water
savings and greenhouse gas emission savings," Campbell said. "Rice is
so important across the whole of Asia that if one could implement this
technology in many different places, you could have significant
reduction in methane production."
But as with MAR, the details of
this technology will have to be worked out before it can be widely
implemented. For example, Campbell said, farmers must put much more
effort into water management; at the moment there are no incentives to
encourage them to do so. In other cases, large numbers of farmers would
have to coordinate their flooding and drying cycles for it to be most
effective.
Long-Term Management
While
promising technologies, neither MAR nor rice drying will be enough to
resolve all of the agricultural problems that scientists predict will
accompany climate change, experts say.
"To mitigate negative
effects of climate-induced floods and drought require the application of
integrated management concepts that have been developed in the past
years and are now increasingly applied," said Wolfgang Grabs, a
hydrologist with the United Nations World Meteorological Organization, a
co-sponsor of the Bangkok workshop.
"These include both
structural and non-structural methods," Grabs said, "such as dykes and
levees, land use planning, storage facilities for water, improved
forecasting and management of water resources, as well as suitable
climate change adaptation approaches."
CGIAR's Campbell agreed. "I
don't think there's going to be a silver bullet," he said. "You're
going to have to do many different things."
Ker Than@National Geographic News
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