Download Vietnam Climate Change Vulnerability Profile

USAID Mekong Adaptation and
Resilience to Climate Change
VIETNAM CLIMATE CHANGE
VULNERABILITY PROFILE
BASED ON THE USAID MEKONG ARCC CLIMATE CHANGE IMPACT AND ADAPTATION STUDY
The area of the Lower
Mekong Basin (LMB) found
in Vietnam includes both
the Delta and the Central
Highlands, two distinct
regions of importance to
the country’s economy
and culture.The results of
the USAID Mekong ARCC
Climate Change Impact and
Adaptation Study indicate
these regions will experience
pronounced changes under
future climate conditions
related to: significantly higher
temperatures, changes in the
extent and distribution of
rainfall, and sea level rise (SLR).
Figure 1: Projected average maximum daily temperature
change in the Lower Mekong Basin including the Vietnam
Central Highlands and the Mekong Delta.
Key findings include the following:
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Annual mean temperature will rise by 3°C with daily maximum temperatures exceeding 40°C
in some years (Figure 1); expected ramifications include significant decline in crop yields, reduced
livestock productivity, and loss of NTFPs.
Annual rainfall will increase in the Vietnam portion of the LMB with wet season rainfall increasing up
to 20% in the Central Highlands (Figure 2); the increased rainfall will cause widespread flooding during
already wet periods with associated effects such as landslides, loss of crops, and reduction in yield.
Relatedly, extreme rainfall events and associated flooding will occur more often. For example, in the
Central Highlands, the number of large rainfall events (exceeding 100 mm/day) is expected to double
in frequency compared to baseline occurrence.
Meanwhile, dry season months will generally become drier, prolonging water stress; in the Delta, for
example, drought will occur 80% of the years in April compared to 60% under baseline conditions.
The compounded effects of SLR and increased rainfall throughout the LMB catchment during the wet
season will result in annual floods of significantly greater depth and duration in the Delta.
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Figure 2: Projected increases in peak daily precipitation in the wet season for the Lower Mekong Basin.
DELTA
Figure 3: Agro-ecological
zones in the Mekong Delta.
The delta encompasses several distinct agro-ecological zones (Figure 3) including
freshwater alluvial wetlands along the upper portion of the Mekong’s distributary
channels (green shade in figure); acidic peatlands to the west and east of the Mekong
channels (pink); and mangroves and saline coastal areas to the south (yellow). These
three zones drive some marked differences in crop types and calendar in the delta.
For example, in the freshwater zone, intensive triple rice crop farming is prevalent,
while along the saline coastal zone, an annual rice-shrimp rotation is more common.
The Mekong Delta Flood Regime
SLR and increasing average flood volumes along the Mekong mainstream will increase the depth and
duration of average floods in the Mekong Delta. Large areas of the delta that were historically rarely
or never flooded to depths of 1.0 m and 0.5 m are projected to be regularly inundated to these levels.
Maximum flood depths are projected to increase by over 1.0 m with the highest increases along the South
China Sea coastline.
The culmination of increasing average flood flows and SLR will significantly alter the flooding regime of the
delta as described below:
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Approximately 19% of the total delta area (600,000 ha) that historically was rarely or never flooded to
a depth of 1.0 m will experience floods at this level or greater for four or more days during an average
flood year.
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The area of the delta that is rarely or never flooded to a depth of 0.5 m or greater during an average
flood year will change significantly - from nearly 60% to only 10% of the total delta area (1.9 million ha
to 300,000 ha).
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There will be a sharp increase in the area of the delta that is inundated to 0.5 m for over 121 days
from 75,000 ha to close to one million ha.
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During an average flood year the area of delta flooded to over 1.0 m depth will increase from 45%
to 57% under projected climate conditions – an increase of over 650,000 ha (Figure 4).
Figure 4: Comparison of flood depth in
the Vietnam Delta for baseline and climate
change conditions.
Climate Change Threats and Sectoral Vulnerabilities in the Mekong Delta
As SLR increases in the future, some areas of the delta that were not previously affected by salinity
intrusion will become so, particularly during the dry season from January to April. Such a change will
require the use of saline-tolerant rice varieties or a reduction in rice production from three to two rice
crops per year. Without saline-tolerant varieties, rice yields could decrease by almost 50% in the case of mild
saline water intrusion.
In provinces such as Kien Giang, Bac Lieu,
and Ca Mau where seasonal salinity intrusion
is common, salinity control infrastructures
(embankments and sluice gates) have been
developed to protect and maximize rice
production in freshwater areas. With increasing
SLR, these areas will be more affected by
saline intrusion possibly requiring a shift in the
cropping system and cropping calendar and a
switch to brackish water aquaculture.
As outlined above, SLR will also affect the
duration and amplitude of the delta flood
regime. Extreme flooding events or early
flooding in August has been known to affect
the harvest of the second wet season rice
crop. Rice production will be increasingly affected
by excessive flooding in the tidally inundated
areas and through longer flooding periods. These
adverse impacts could affect all three cropping
seasons.
Climate change related impacts to the Mekong Delta’s fishery include increased temperatures, fluctuating
salinities, and excess flooding. Increased temperatures can result in compromised water quality within
aquaculture ponds. Increased flooding during the rainy season will require higher pond embankments and
increased farm construction and maintenance costs. Flood events can also result in dramatic swings in
salinity levels, negatively affecting shrimp production.
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CENTRAL HIGHLANDS
The Central Highlands of Vietnam is a dynamic agricultural region, with both traditional systems based on
rainfed rice farming and a more recent industrial agriculture based on rubber, cassava, maize, sugarcane, and
robusta coffee production.
Coffee production in the Central Highlands is mostly concentrated in Gia Lai and Dak Lak Provinces, which
are well suited to coffee growing as a result of climate and soil conditions.
During the past decade, the planted area of irrigated rice, maize, cassava, and sugarcane has also been
expanding in provinces such as Gia Lai and Dak Lak. In Gia Lai Province, for example, the area planted with
cassava has grown by about 13% per annum for the last 10 years. A similar rate of growth is found for
maize (10% p.a.). These trends are the result of growing market demand and higher prices for commercial
crops.
Climate Change Threats and Sectoral Vulnerabilities in the Central Highlands
Both the industrial and traditional agricultural systems of the Central Highlands will be vulnerable to
changing climate factors. Significant increases in daily maximum temperatures (for example, up to 5°C higher
during the wet season in Gia Lai), as well as changes in the frequency and intensity of extreme rainfall events
will have significant implications for all livelihood sectors. Rainfall in the 3S basin is predicted to increase
during the wet season by 11%, and decrease by as much as -10% during the dry season. Crops such as rice
and robusta coffee will face severe threats from high temperatures during their growth cycle. Increased
temperatures will also induce higher water demands particularly during the dry season, which is projected
to get even drier in the future. Without adaptation, crop yields will be notably affected; for example,
significant areas in the Central Highlands are predicted to be less suitable for cassava, robusta coffee, and
rubber culture by 2050 assuming continuation of current agricultural systems and practices (Figures 5 and 6).
Figure 5: Baseline and 2050 land suitability for rubber in the Lower Mekong Basin.
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Figure 6: Baseline and 2050 land suitability for robusta coffee in the Lower Mekong Basin.
The ongoing industrialization of crops in the hill terrain of the Central Highlands has resulted in negative
environmental consequences such as erosion and reduced soil fertility. The increasing frequency and
intensity of extreme rainfall events that is projected for this region will only exacerbate these issues. Rainfall
events larger than 100 mm/day are projected to double in frequency by 2050 in Gia Lai, for example, resulting
in more flooding in narrow upland valleys, increasing erosion and landslides, and the washing out of crops.
Meanwhile, expansion of the number of farmers raising fish in small ponds and rice fields in the Central
Highlands will likely continue as wild fish catches decline due to hydropower development. However,
weather events such as droughts and flash flooding may present farmers with challenges for maintaining
infrastructure and stocks as these extreme events continue to become more frequent.
Livestock concerns include compromised productivity of both small-scale and commercial pig systems due
to increasing temperatures. Reproduction rates and natural disease immunity will decline as the animals
are stressed due to factors such as water shortages and lack of suitable ventilation. Flash flooding will affect
cattle production due to herd loss and increased spread of disease.
POTENTIAL ADAPTATION OPTIONS
Agriculture
Adapting the agriculture sector to climate change in both the Mekong Delta and Central Highlands will
involve a mix of strategies, possibly including:
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Strengthening the resilience of both rainfed and irrigated rice-based systems through adoption of
improved varieties and better management practices and reducing vulnerability to extreme climate
events. This could include the use of specific varieties to mitigate the impact of flooding and extreme
heat, as well as varieties that are tolerant to saline water.
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Adopting/improving water efficiency and water management practices (water harvesting, small–scale
irrigation, etc.) in drought-prone areas such as in the Central Highlands in order to alleviate the
impacts of water shortages.
Improving soil fertility and soil management of both cash and subsistence systems such as improved
erosion control techniques and intercropping.
Promoting agricultural diversification and mixed farming systems to mitigate current reliance on
monocultures.
Livestock
The improvement of livestock development and resilience to climate change falls into five broad strategies:
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Nutrition: The quality and quantity of feed production, storage, and the nutritional balance of diets
needs to be increased to reduce undernourishment.
Disease resistance: Internal resistance needs to increase to reduce the threat of disease through
improvement of nutritional status, body condition, and vaccination levels. It also requires improved
biosecurity to prevent the movement of diseases onto and off farms and to reduce the risk of
pathogens entering the herd or flock.
Housing: Location and design should maximize natural ventilation and minimize exposure to extreme
events.
Production planning and offtake: Reducing inbreeding, earlier weaning, and strategic offtake plans can
increase resilience of livestock systems.
Access to markets: Improved access to input and output markets and producer organizations would
reduce input costs, increase prices received, and reduce price volatility.
Fisheries
Aquaculture -- due to its diversity of systems, scales of production, inherent manageability, and control
of environments -- potentially offers more scope for adaptation to climate change than capture fisheries.
Adaptation strategies for aquaculture may include:
• pond aeration to mitigate the effects of increased temperature;
• on-site water storage to reduce the risks of reduced water availability during the dry season;
• re-use of pond water also for water conservation and to mitigate the release of effluents to the
environment;
• strengthening of embankments to protect against flooding will be necessary for ponds in many
areas;
• diversion canals may also have to be dug to channel water away from vulnerable pond areas; and
• more climate-friendly systems, (e.g., tiger shrimp/crab production in mangrove replanted areas of
the delta), should be utilized and promoted more widely.
Regardless of the livelihood sector, successful adaptation will require flexibility and a diversity of
approaches to adapt to shifting conditions.
USAID Mekong Adaptation and Resilience to Climate Change (USAID Mekong ARCC)
11 Floor, Mahatun Plaza Building, 888/118 Phloenchit Road, Lumpini, Pathumwan, Bangkok, 10330, Thailand
Tel: +66.2.650.9919 to 21
Fax: +66.2.650.9922
E-mail: [email protected]
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Source: http://www.mekongarcc.net/resource
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