As
loyal readers of ExSE have probably noticed by now, this site, at its core, is
dedicated to Mekong River and the people who are connected to it. Thus it seems
odd that so little attention has been given to the Mekong Delta on ExSE. As is
the case with most international coverage of the Mekong, the upper and lower
reaches of the river are largely ignored in favor of stories about hydropower
projects and the livelihoods they will affect.
However, the challenges that the Mekong Delta
(MKD) is currently facing and will face in the future are also serious. These
challenges are directly related to global warming and are shared with other
deltas, though the unique geography and ecology of the Mekong makes the
consequences of climate change here even graver.
The
Delta itself is an astounding place. Completely contained within the borders of
Vietnam, the region is an agricultural powerhouse. The Delta accounts for half
of Vietnam’s rice production, three-fourths of its fish catch and 70% of the
national fruit harvest while occupying 36,000 square kilometers, only 12% of
Vietnam’s total area. While much of the fish is consumed domestically, rice and
fruit are shipped to countries in Southeast Asia and beyond, contributing to
Vietnam’s status as the world’s second-largest rice exporter.
Historically,
most of the 22 million inhabitants of the Mekong Delta have settled densely
along the three main branches of the Mekong and 90,000 km of canals and
waterways that crisscross the region, with boats greatly outnumbering cars. The
Delta is a highly aquatic environment and the human inhabitants wholly depend
on the local water resource regime for their livelihoods. Unfortunately for
them, the region’s hydrology is changing rapidly.
Precipitation
modification is one area that is affecting the MKD. According to projected data
from the Delta’s Can Tho
University, the rainy season in the 2030′s will start two weeks later on
average and annual total precipitation will decrease by 20% when compared with
measurements from the 1980′s. In addition, the distribution of
precipitation over the rainy season months of May through October has changed.
There is now less rain during the early and middle stages of the season and
heavier rain during the later months of August, September and October. This
runs counter to the water needs of paddy rice.
Monthly Rainfall
Distribution in the Delta: Changes between 1980′s and 2030′s
All
across Southeast Asia, people rely on the May through August rice crop both for
year-round personal consumption and outside income. Like many crops, paddy rice
has specific water needs during each stage of growth. During the first stage,
large amounts of water are needed to soften the fields for plowing. Much less
water is needed during planting, but the required amount increases as the rice
buds and finally flowers in late July andwhen the rice ripens in August, the
need for water decreases. Traditionally, precipitation patterns and water needs
of paddy rice correlated well, however this has changed in recent years. The
new of pattern of drought in the first half of the rainy season and heavy rain
in the later months unbalances the paddy rice cycle and as a result, farmers in
the Delta have been experiencing lower yields of their most vital crop.
Along
with precipitation distribution, the amount of rainfall the Delta receives is
also changing. As mentioned before, modeling indicates that average annual
precipitation the 2030′s will have fallen by 20 mm when compared with 1980
levels. Coupled with modified distribution patterns, farmers will be forced to
resort to expensive water pumping and revised irrigation techniques in an
effort to maintain yields. However, this drop in rainfall will be short-lived.
Research done by the International Panel on Climate Change (IPCC) shows that
this trend will reverse in the 2050′s and average precipitation will double by
2070, posing completely different challenges for farmers.
Predicted change in
precipitation for 2030′s when compared with data from 1980′s.
Unfortunately,
changing precipitation levels are not the only aspect of climate change that is
affecting the Delta. Across the world, temperatures are increasing and southern
Vietnam is no exception. Based on modeling by the IPCC the average temperature
in the MKD will increase by 1°C between 2010 and 2039. Further modeling indicates
that the Delta will become an oven by 2080, with average temperatures 3-4°C
higher than 2010 levels. Furthermore, the annual number of days over 35°C is
set to double by 2030, when compared with numbers from the 1980′s.
Aside
from more active sweat glands and a boon for the air conditioner industry,
these numbers have real consequences for the people of the Mekong Delta, especially
because hotter temperatures affect their crops. According to research done in
the last decade, the average minimum temperature of an area and its rice
production are correlated; for every 1°C increase in minimum temperature,
average rice yields fall by 10%. When coupled with the data on climate change
in the MKD, the future of the region’s rice production is bleak. Average yields
will decrease by almost 10% by the 2030s and by the 2080s, and the Delta’s rice
production will only be 60% of its 2010 levels. In addition, changes in
precipitation patterns might also have a negative effect on rice harvests, only
exacerbating the impacts of rising temperatures.
However,
Delta farmers in the 2070s may not have to worry about crop yields because by
then, there might not even be fields to plant seeds in. There are two
interrelated reasons for this possibility: salinity intrusion and coastal and
riverbank erosion. Salinity intrusion poses a danger to agriculture because
almost all crops, like rice and tropical fruit, need fresh water to grow;
saltwater intrusion damages the water table and the land above it used for
farming. In recent years, salinity intrusion has increased in intensity and
scope. Comparing levels measured in 2005 and 2010, researchers from Can Tho
University found that salinity intrusion more than doubled, reaching 70 km
upstream. What used to be a problem only for the most coastal of Delta farmers
has now become a danger to almost half the region.
With increased sea
levels rise (SLR), saltwater makes deeper incursions into the Delta, leading to
overall higher salinity levels (measured in grams/liter).
Rising
sea levels and a changing river course both contribute to salinity
intrusion. Rising sea levels are a
global phenomenon that has been well documented but its effects vary by
location and the MKD is an especially hard hit area. It is ranked as the most
vulnerable delta in the world by the IPCC, and with good reason as the Delta
could lose significant portions of livable land in the coming decades. Based on
geography and population distribution, the MKD will lose 25% of its land with
one meter of sea level rise and a two meter rise will take away half. With
livable land already scarce, just a one meter rise would leave 3.5 million Delta
residents homeless.
As the
sea levels rise, more salt water enters into the farmland, especially during
times when high tides are stronger. Salinity intrusion is only exacerbated by
the Mekong’s flow modification. Increased irrigation and a string of already-built
and planned hydropower projects on the Mekong and its tributaries are
decreasing the flow rate of the river in the MKD. This weakens the Delta’s
capacity to resist incursions by the sea. What’s more, the same irrigation and
hydropower projects also decrease the amount of sediment that reaches the
Delta. Thus when the tides finally retreat from the Delta, vital nutrients that
could help replenish the soil are lacking.
Unfortunately
for the 22 million residents of the Delta and tens of millions more that depend
on their crops, these are only a few of the environmental problems facing the
region. Increasingly erratic flood cycles and intense tropical storms are just
two more. Socio-economic problems also plague the region and from the look of
environmental modeling, the window to solve these issues is rapidly closing. At
the same time, such a dynamic environment offers great opportunities for study
and experimentation, both of which could benefit delta regions globally. The
forecast for the MKD is not good, but there are possible solutions, some more
conventional than others. In the coming weeks, look for more discussion on the
issues facing the Mekong Delta, only from ExSE.
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