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USAID Mekong Adaptation and
Resilience to Climate Change
CAMBODIA CLIMATE CHANGE
VULNERABILITY PROFILE
BASED ON THE USAID MEKONG ARCC CLIMATE CHANGE IMPACT AND ADAPTATION STUDY
The Lower Mekong Basin (LMB) encompasses the major part
of Cambodia including the globally unique Tonle Sap Lake
and associated floodplains; the 3S Rivers Basin, an important
tributary network that drains into the Mekong; and the plains
of Mondulkiri Province that border Vietnam in the southeastern
part of the country. The results of the USAID Mekong ARCC
Climate Change Impact and Adaptation Study indicate that
Cambodia will experience pronounced changes in rainfall and
temperature patterns by 2050 with significant ramifications for
ecosystems, and communities and the livelihoods that support them.
Figure 1: Projected annual average maximum daily temperature and annual precipitation changes in the Lower Mekong
Basin
1.
Key findings include the following:
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Annual daily maximum temperatures will rise by roughly 2°C to 4°C in Cambodia (Figure 1) with
higher increases during certain months of the year.
Eastern Cambodia provinces such as Mondulkiri will experience some of the largest increases in
temperature projected for the LMB with significant impacts on agriculture, livestock and fisheries,
and non-timber forest products (NTFPs) (Figure 1); more precipitation during the traditional growing
season will also impact crops through increased flooding, waterlogging of soils, and higher incidence of
fungal disease and pests.
Large rainfall events will occur more frequently, particularly during the already wet rainy season. The
projected rainfall in the 3S Rivers Basin, for example, will increase by 11% during the rainy season
while decreasing by 3-10% in the dry season. Cambodia in general is dominated by lowland plains and
plateaus; increased frequency of large storms will result in more flooding and related costs, especially
in low-lying areas such as the extensive floodplains surrounding Tonle Sap Lake including southern
and central parts of Kampong Thom Province.
The projected changes in the timing and extent of rainfall in Cambodia will present challenges to
livelihood productivity such as increased waterlogging of crops during the growing season, e.g.,
affecting lowland rice, soybean, and cassava; and increased livestock exposure to disease and floodrelated population loss, e.g., affecting scavenging chickens, and smallholder cattle and buffalo. Extension
of drought at the end of the dry season will impact the availability of critical fisheries habitat
components such as refuge pools for migratory fish; and will reduce water quality in aquaculture
ponds. Additional heat stress during the dry season will impact the productivity of NTFPs such as false
cardamom, wild orchid, and rattan.
KAMPONG THOM PROVINCE AND THE TONLE SAP REGION
Kampong Thom Province is located in the
central part of Cambodia between Tonle
Sap Lake to the west and the Mekong River
mainstream to the east. With climate change,
daily maximum temperatures will increase
between 2°C to 4°C throughout the year.
Under baseline conditions, for example,
daily maximum temperature for a typical
year peaks in March at approximately 33°C.
Under climate change, daily maximum
temperatures in Kampong Thom will
typically exceed 35°C in March-April
(Figure 2), which will have serious effects
on crops, livestock, and other livelihood
sectors.
Increasing precipitation during the rainy
season (e.g., up by 40 mm per month
in September) may also have significant
impacts on crops such as cassava and
soybean (Figure 3).
2.
Figure 2: Daily maximum temperature for a typical year in Kampong Thom Province. The blue solid line represents
baseline (BL) average, and the orange solid line represents the future average as projected by global climate models
(GCM).
Typical Year
Figure 3: Monthly precipitation for a typical year in Kampong Thom Province, Cambodia.
Month - typical year
3.
Climate Change Threats /Sectoral Vulnerabilities in the Tonle Sap Region of Cambodia
Tonle Sap Lake and the surrounding floodplains are affected by strong seasonal inundation patterns; during
the wet season the lake historically expands to roughly 15,000 km2, while during the dry season it shrinks
to approximately 2,500 km2. This dynamic influences livelihoods in surrounding provinces; flooded rice
fields during the wet season serve as an important small-scale fishery and provide a vital cash source to
rural households. As the lake shrinks during the dry season, crops are grown for subsistence and cash.
Additionally, the culture of fish in cages in Tonle Sap Lake is one of the oldest aquaculture systems known
in the world and is of critical importance to local livelihoods. The downstream multi-species migration from
Tonle Sap to the mainstream Mekong also supports the commercially important bagnet fishery, which is of
great significance to the region’s economy.
Kampong Thom Province is located adjacent to Tonle Sap Lake and is affected by flooding in the southern
and central parts of the province. Rice, soybean, and cassava are the most vulnerable commodities there
due to increased temperature and higher incidences of floods under future conditions. Lately, there has
been an expansion of rubber cultivation in both industrial concessions and smallholder farms in Kampong
Thom, which will also likely be significantly impacted by future climate conditions including higher
temperatures and increased rainfall. The main threats and vulnerabilities for crops in Kampong Thom are
outlined in Table 1.
Table 1: Main threats and vulnerability for crops in Kampong Thom Province, Cambodia
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Vulnerable
Crop
Threat
Lowland
rainfed rice
Increased
temperature
Impact Summary
Vulnerability
More than 75% of the daily maximum
temperatures will be above the optimal zone for
lowland rainfed rice.
High
Irrigated rice
More than 50% of daily maximum temperatures
will be above 35°C in March and April affecting
irrigated rice.
High
Soybean
Extreme maximum temperatures higher than
35°C will occur during soybean crop growth.
High
Lowland
rainfed rice,
Cassava,
Soybean
Flooding
Flood prone area around the Mekong and
Tonle Sap Lake in the southwestern part of the
province. Monthly precipitation increase of 18% in
September will result in increased waterlogging.
High
Soybean
Decrease in water availability will be between 4%
Decrease in
water availability and 10% during the crop growth period.
High
Increased flooding may affect lowland rainfed rice at the end of the crop cultivation before harvesting,
potentially resulting in total loss of the culture. Late crops of soybean may also be affected by flooding,
especially during the harvest period as they require dry conditions. More than 12,000 km2 of land
within Kampong Thom Province will see a decline in soybean’s climate suitability by 2050 (Figure 4).
Cassava culture will also be threatened by flooding and increased rainfall and subsequent waterlogging
that reduces yield and facilitates the spread of disease.
4.
Figure 4: Baseline and 2050 land suitability for soybean in the Lower Mekong Basin with planting date in May and crop
duration 120 days.
Figure 5: Baseline and 2050 land suitability for rubber in the Lower Mekong Basin.
5.
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Increased temperatures will affect both dry and rainy season rice crops and, coupled with an increase in
rainfall, the decline in yield is estimated to be about 3.6% in Kampong Thom. This equates to reductions
of output of up to 15,000 tonnes of rice in the province compared to the 2010 baseline. Increases
in temperature will also affect soybean culture, leading to a drop in yield. The increase in rainfall and
temperature will reduce the suitable areas of rubber (Figure 5), which has recently expanded in the
province.
Subsistence fishing is a critical source of food security in the Tonle Sap and surrounding floodplains,
even if fishing is not a household’s principal activity. Commercial fishing (including aquaculture) as a
primary or secondary activity is common amongst many households. Higher temperatures will likely
affect the productivity of both capture fisheries and aquaculture in the Tonle Sap region. Loss of dry season
refuge pools in hydrologically connected rice fields, and reduced water quality in aquaculture ponds are
primary concerns.
Livestock may see reduced reproduction rates and immunity due to heat stress, and increased spread of
disease and herd loss due to increased flood events.
MONDULKIRI PROVINCE AND EASTERN CAMBODIA
Mondulkiri Province in southeastern Cambodia will experience large relative increases in temperature,
particularly during the wet season when an increase of almost 20% can be expected to the south (Figure 6).
Figure 6: Mondulkiri Province projected change in wet season temperature.
6.
The average daily maximum temperature in Mondulkiri will rise from roughly 31°C to 36°C during the dry
season month of April. In more extreme years, dry season temperatures may exceed 44°C. The increase in
both average and extreme temperatures will have potentially devastating impacts on crops, livestock, and
human health.
Monthly precipitation is projected to increase for all wet season months in Mondulkiri, with a particularly
significant increase of almost 70 mm expected for the month of October (Figure 7). Meanwhile, a reduction
in rainfall is projected for the dry season months of December through April. Overall, annual rainfall in
Mondulkiri is projected to increase by 173 mm (1,943 mm/yr to 2,116 mm/yr). However, the expected
seasonal distribution of the rainfall will result in two distinct phenomena consisting of increased flooding during
the wet season, and extended drought during the dry season.
Figure 7: Monthly precipitation for a typical year in an upland area of Mondulkiri, Cambodia.
Month - typical year
Climate Change Threats and Sectoral Vulnerabilities in Eastern Cambodia
The vulnerabilities of the main crops cultivated in eastern Cambodia are related to effects from storms
and increased precipitation, as well as higher temperatures and decreased soil water availability during
periods of the year (Table 2).
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Crop yield modeling estimates a decrease of 3% in rainfed rice yield in Mondulkiri, or about 1,114
tonnes per year for the province. The climate suitability modeling showed a decrease in suitability for
all the crops assessed in Mondulkiri; particularly the industrial crops including cassava, rubber, coffee,
and soybean. This could potentially strain the expansionary trend of commercial agriculture in the
province and impact on opportunities for the improvement of livelihoods. Decreases in crop suitability
in eastern as well as the majority of Cambodia will affect significant areas available for many crops
including rubber (Figure 5).
7.
Table 2: Main threats and vulnerability for crops in Mondulkiri Province, Cambodia
Vulnerable
Crop
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Threat
Impact Summary
Vulnerability
Increasing frequency of storms >100 mm/
day. Precipitation above 500 mm per month in
October. Increased precipitation may damage
crops and create waterlogging in lowland areas
that are more exposed.
Medium to
High
Cassava,
Soybean,
Lowland
rainfed rice
Storms and
increased
precipitation
Soybean
Decreased water Decrease in soil water availability will be between
18% and 20% during the crop season creating
availability
water stress.
High
Rice
Increased
temperature
Increase in maximum temperature will fall
between 12% and 17% compared to baseline
conditions during growth period. More than 50%
of the maximum daily temperatures will be above
the optimal zone for rainfed rice.
Medium
Cassava
Increased
temperature
Around 15% of the days will be above 35°C
during the growth cycle of cassava.
Medium
Rubber
Increased
temperature
Dry season (March to May) will have more days
above 35°C as daily maximum temperatures with
temperature increases of 17% in May.
Medium
Soybean
Increased
temperature
Higher maximum temperature in the rainy season Medium
will limit yield. This might be a stress for soybean in
the case of the early wet season crop in April or
May.
Fisheries in eastern Cambodia will be affected by increased temperatures and changes in rainfall patterns.
Migratory white fish may be impacted by the loss of suitable refuge pools due to higher temperatures
and decreased precipitation during a portion of the dry season. Higher temperatures will affect the
water quality of aquaculture ponds while increased flash flood events will decrease stocks and impact pond
infrastructure.
Livestock impacts include reduced
reproduction and immunity due to
heat stress, and secondary impacts
related to decreased fodder
availability. Increasing flood events
will accelerate the spread of disease
and herd loss. In eastern Cambodia,
smallholder cattle/buffalo systems
are the most vulnerable to
temperature.
8.
POTENTIAL ADAPTATION OPTIONS
Agriculture
Adapting the agriculture sector to climate change in Cambodia 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 the shifting of cropping calendars to avoid harvest during periods of high rainfall.
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 trends of 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
Due to its diversity of systems, scales of production, inherent manageability, and control of environments,
aquaculture potentially offers more scope for adaptation to climate change than capture fisheries.
Strategies for the fisheries sector include:
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Pond aeration to mitigate the effects of increased temperature;
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On-site water storage to reduce the risks of reduced water availability during the dry season;
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Strengthening of embankments to protect against flooding will be necessary for ponds in many areas;
and
Construction of diversion canals to channel water away from vulnerable pond areas.
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)
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