GIS-BASED CROP SUITABILITY AND CLIMATE CHANGE
VULNERABILITY OF FARMING SYSTEMS
IN CAGAYAN VALLEY
Januel P. Floresca1 1Isabela State University, Echague, Isabela, 3309, Philippines
Email: [email protected]
KEY WORDS: GIS-based crop suitability analysis, climate change vulnerability, farming systems
ABSTRACT: Geographic information system (GIS) is a tool capable of facilitating assessment of vulnerability to the
impacts of climate change of farming systems and analyzing crop suitability of crops for agroforestry establishment to
enhance the resiliency of existing farming systems. The study was aimed to assess the vulnerability of existing rice
and corn farming systems to the impacts of climate variability and extremes and to assess the suitability of tropical
fruits to be introduced for the establishment of agroforestry farming systems using GIS. The weighted rating model
(equal weights) was used in overlaying thematic maps following the IPCC framework that vulnerability is a function
of exposure, sensitivity and adaptive capacity. Results indicated Echague, Isabela had the highest land area with high
vulnerability of 99,726.53 ha, followed by Penablanca with 22,872.85 ha, then by Maddela with 7,737.87 ha and
Bagabag as the lowest with only 378.85 ha. For the four study sites, most of the land area had low vulnerability with
298,862.93 ha, followed by moderately vulnerable with 176,250.34 ha while the lowest was highly vulnerable with
130,716.10 ha. Babaran, Echague, Isabela had the highest climate change vulnerability index considering that the
main crop is only corn exposed to more frequent typhoons and drought. Results also indicated that all the tropical
fruits (rambutan, Mango, lanzones, pummelo) and bamboo were suitable to be planted in all the municipal study sites
and selected model farms based on the ecological requirements of each. Tropical fruits and bamboo are suitable in
climate change-vulnerable areas in Cagayan Valley. The GIS climate change vulnerability maps should be
disseminated to LGUs and vulnerable communities to enhance their awareness and utilize the information for
planning and decision-making on climate change-resilient farming system development.
1. INTRODUCTION The Cagayan Valley Region (where the Cagayan River, the longest river in the country of approximately 490 km long
is located) is geographically positioned adjacent the Pacific Ocean that made it exposed to the wide area climate
variability and extremes such as intensified and more frequent tropical cyclones, monsoon rains as well as the El
Niño-La Niña Southern Oscillation (ENSO) oceanic phenomenon that cause floods, flashfloods and landslides/soil
erosion, and droughts. Cagayan Valley is considered as one of the most vulnerable regions to climate variability and
extremes particularly typhoons and floods in the Philippines based on the collaborative action research titled
“Enhancing the climate change adaptive capacities of LGUs and Scientists in the Philippines” conducted by
CPAF-UPLB with ISU as their research partner. Results confirmed high degree of adverse impacts of typhoons and
monsoon rains on flooding affecting smallholder rice and corn farmers.
The identification of the areas most vulnerable to climate change risks in the Country is among the most urgent of
policy needs based on the National Framework Strategy on Climate Change (NFSCC) formulated by the Climate
Change Commission (CCC) in accordance to Section 13 of the Philippine Climate Change Act of 2009 or RA 9729
which is to assess risks and impacts of climate change and identify the most vulnerable communities, areas and
ecosystems. Moreover, Section 6(d) of the Philippine Disaster Risk Reduction and Management (PDRRM) Act of
2010 or RA 10121 ensures a multi-stakeholder participation in developing, updating and sharing DRRM information
through GIS-based risk mapping policy, planning and decision-making tools for science-based analysis and
information on geographically targeted interventions on climate change adaptation, mitigation and disaster
preparedness.
Agroforestry theoretically depicts a climate change-resilient farming system in terms of its ability to sustain
productivity in the face of recurring climate variability and extremes. The ecosystem services of agroforestry being
more diverse coupled with existence of water harvesting/impoundments offer opportunities to reduce the adverse
effects of extreme climate events. Tropical fruits and bamboo/forest trees serve as windbreaks and soil erosion/runoff
control during typhoons and monsoon rains. Backyard crops such as root crops provide alternative food and income
during calamities to take the place of field crops (rice and corn) that have higher risks of damage. Water
impoundments/groundwater provide available irrigation and potable water during periods of drought. Thus,
vulnerability of farming systems to the impacts of climate change are reduced and become climate change resilient.
From overlaying various spatially-referenced biophysical and socioeconomic factors (e.g. topography, soil, climate,
land use, demographic profile, farming practices, problems and constraints), GIS is capable of analyzing crop
suitability for any agroforestry crop (tropical fruits and bamboo) in a given geographic region using sets of criteria
based on ecological requirements.
The study aimed to assess the climate change vulnerability of existing farming systems using geographic information
system (GIS) and crop suitability of agroforestry crops (tropical fruits and bamboo) as intervention for enhancing the
climate change resiliency of existing farming systems in the study sites.
2. METHODOLOGY
2.1 Selection of Study Sites
Using the set criteria on high risk municipalities for floods, landslides and typhoons in Cagayan River basin identified
by DENR-MGB and accessibility being near the national road, four LGUs were selected namely: Penablanca,
Cagayan, Echague, Isabela, Maddela, Quirino and Bagabag, Nueva Vizcaya (Figure 1).
Figure 1. Selected study sites.
2.2 Climate Change Vulnerability Mapping
The climate change vulnerability mapping procedure of Yusuf and Francisco downscaled at Cagayan Valley was
adopted following the IPCC framework that vulnerability is a function of exposure, sensitivity and adaptive capacity
as follows:
1) Assessment of exposure using information from historical records of climate-related hazards as past exposure to
climate risks are considered as the best available proxy for future climate risks. Climate hazard maps for the
climate-related risks include tropical cyclones, floods, landslides, and droughts;
2) Use of population density as a proxy for human sensitivity to climate-hazard exposure. The assumption here is that
regions that are relatively less inhabited will be less vulnerable compared to regions with high population densities,
given the same degree of exposure to climate hazards;
3) In addition to the human aspect of vulnerability, ecological sensitivity of the region using biodiversity information
is included as a proxy variable. A biodiversity-rich region, measured by the percentage of protected areas, is thus
considered here as more vulnerable than other areas to climate hazards, other things being equal; and
4) Adaptive capacity is defined as the degree to which adjustments in practices, processes, or structures can moderate
or offset potential damage or take advantage of opportunities (from climate change). It is a function of
socio-economic factors, technology and infrastructure.
Cartographic Model – Exposure Map
TYPHOON HITS
1=L; 2=M; 3=H
TEMPERATURE
INCREASE
1=L; 2=M; 3=H
RAINFALL
INCREASE
1=L; 2=M; 3=H
RAINFALL
DECREASE
DUE TO EL NINO
1=L; 2=M; 3=H
FLOOD-PRONE
AREAS
1=L; 2=M; 3=H
EROSION-PRONE
AREAS
1=L; 2=M; 3=H
CLIMATE RISKS
MAP1=L; 2=M; 3=H
MULTI-HAZARD
MAP1=L; 2=M; 3=H
EXPOSURE
MAP
1=L; 2=M; 3=H
Intersect
Intersect
Merge
0.4
0.6
0.4
0.3
0.2
0.1
0.6
0.4
Reclass
Reclass
Reclass
Cartographic Model – Sensitivity Map
POPULATION/
AREA
(No. of indiv./ha)
BUILT-UP
AREAS
1=L; 2=M; 3=H
PRIME AGRIC’L
LANDS
1=L; 2=M; 3=H
FORESTS/
PROTECTED
AREAS
1=L; 2=M; 3=H
POPULATION
DENSITY1=L; 2=M; 3=H
LAND USE
SENSITIVITY
1=L; 2=M; 3=H
SENSITIVITY
MAP
1=L; 2=M; 3=H
0.3
0.4
0.2
Reclass
Calculate
Reclass
Reclass
Merge
0.6
Intersect
0.4
OTHER LAND
USES
1=L; 2=M; 3=H
0.1
The cartographic models (Figures 2-5) indicate the map layer inputs, the geoprocessing used (reclassification,
intersect) and the resulting output composite maps such as exposure, sensitivity, adaptive capacity and overall climate
change vulnerability.
Figure 2. Cartographic model for exposure map.
Figure 3. Cartographic model for sensitivity map.
Figure 4. Cartographic model for adaptive capacity map.
Cartographic Model – Adaptive Capacity Map
HDI
1=L; 2=M; 3=H
POVERTY
INCIDENCE
1=H; 2=M; 3=L
INCOME GAP
1=H; 2=M; 3=L
TECHNO-GABAY
(FITS+MS) CENTERS
1=L; 2=M; 3=H
SOCIO-
ECONOMICS
MAP
1=H; 2=M; 3=L
INFRA-
STRUCTUREMAP
1=H; 2=M; 3=L
ADAPTIVE
CAPACITY
MAP
1/3=H; 1/2=M; 1/1=L
TECHNOLOGYMAP
1=H; 2=M; 3=L
TELECOMS (GSM &
G3 COVERAGE)
ELECTRICITY
eq
ual w
eig
hts
0.6
Reclass
Merge0.2
0.2
0.6
Reclass
Reclass
Reclass
Merge
Merge
HEALTH CENTERS/
HOSPITALS
ROAD DENSITY
HOUSE & LOT
IRRIGATION
SAFE WATER
SOURCE
STRONG HOUSES
0.4
0.2
0.4
Figure 5. Cartographic model for overall climate change vulnerability map.
3.3 Multi-criteria Crop Suitability Analysis
Mapping of the biophysical conditions of selected farming systems using GPS and available geo-referenced digital
maps and digital elevation model (DEM) and linking attributes on ecological requirements of tropical fruits such as
climate (temp, rainfall), elevations and slope, and soil types (Table 1) as follows:
Table 1. Basic ecological requirements of selected tropical fruits.
Tropical
Fruit/ Bamboo
Topography (Elevation & Slope) Requirements
Soil Requirements Climate Requirement
Mango Flat to slightly rolling terrain
Should not be higher than 600 meters above sea level as it delays fruit maturity at higher elevations.
400 meters ideal for growing mango
Sandy loam,relatively rich in organic matter
Good drainage (very important)
pH 6.0-7.0
Distinct wet and dry season (4 to 5 months dry priod)
Temperature of 21 to 30 degree celsius
No strong winds
Sweet Tamarind
The tree tolerates a great diversity of soil types, from deep alluvial soil to rocky land and porous, oolitic limestone.
It withstands salt spray and can be planted fairly close to the seashore.
Distinct wet and dry season.
Dry weather is important during the period of fruit development.
Pummelo 400 meters ideal for growing pummelo.
The best orchards are situated on the banks of current and former river courses.
It can tolerate a wide range of soils from coarse sand to heavy clay.
Optimum pH from 5.5 to 6.5
Optimum temperature of 25-30o C
Annual rainfall requirement 1500-1800 mm
Lanzones Should not be higher than
650-750 meters above sea
level.
It prefers soil with good
drainage and water retention;
Rich in organic matter and
slightly acidic.
It cannot tolerate sandy
coastal soils and alkaline
soils.
It thrives best in humid
condition, plenty of
moisture.
Some shade is beneficial
especially during the early
years.
Rambutan Plants can grow at 10-500 m
above mean sea level
It prefers clay loam soil, but
can be grown in a wide range
of soil types.
pH 5 to 6.5.
Not water-logged.
Best grown in the
temperature range between
22C to 35C.
Well distributed rainfall.
Figure 8. Cartographic Model of Biophysical Suitability Analysis
SOIL PH6.5 = H; 5 –6.4 = M;
Below 5 = L
SLOPE0-18%=H;
18-50%=M; Above 50%=L
ELEVATION0-600 masl=H;
600-1,000 masl = MAbove 1,000 =L
LAND USE/COVERIdle/Grasslands=H;
Croplands/plantations=M;
Forests/prime rice/
builtup areas=Not
suitable
TOPO
SUITABILITY1=L; 2=M; 3=H
0.5
0.5
Intersect
TYPHOONFreq > 10 = M; Freq 10
& below + typh tack = M; Freq above 10 = L
0.5
Reclass
IntersectSOIL x
LAND USE
SUITABILITY1=L; 2=M; 3=H
Reclass
0.5
SOIL
SUITABILITY1=L; 2=M; 3=H
BIOPHYSICAL
SUITABILITY
1=L; 2=M; 3=H
Reclass
Reclass
0.5
TEMPERATURE22-28 = H;
Above 28 = M;
Below 22 = L;
0.5
CLIMATE
SUITABILITY1=L; 2=M; 3=H
Intersect
Intersect
Intersect
Reclass
0.5
0.5
0.5
0.5
SOIL TEXTUREClay = H;
Loam = M; Sand = L
RAINFALL200-220 mm = H;
101-199 mm = M;Below 100 mm = L;
TEMP x
RAIN
SUITABILITY1=L; 2=M; 3=H
Reclass
0.5
0.5
Intersect
LAND
SUITABILITY1=L; 2=M; 3=H
0.5
Intersect
Reclass
0.5
Figure 6 presents the cartographic model used in the crop suitability analysis using GIS. Meantime, the crop
suitability was only limited to biophysical (topography, soil and climate) criteria to come up with a composite
biophysical suitability map.
Figure 6. Cartorgraphic model of crop suitability analysis.
3. RESULTS AND DISCUSSION
3.1 Geographic Locations and Areas of
Existing Farming Systems
in Cagayan Valley
The study sites were dominated with rice and corn farming systems (Figure 7).
Figure 7. Dominant farming systems in Cagayan Valley and the Study Sites.
3.2 Climate Change Vulnerability of
Rice and Corn Farming Systems
Figures 8 - 10 are the layers used in generating exposure, sensitivity and adaptive capacity maps in Penablanca,
Cagayan for example.
Figure 8. Layers used in generating exposure map.
Figure 9. Layers overlaid to generate the sensitivity map.
Figure 10. Layers overlaid to generate the adaptive capacity map.
Sensitivity Index of the Study Sites
Study SitesDominant
Farming System
Ave. Area
Planted
No. of
Farmers
Sensitivity
IndexRank
Penablanca Upland Corn 2.0 84 2 1
Echague Upland Corn 1.9 87 2 1
Maddela Upland Corn 1.9 81 1 2
Bagabag Irrigated Rice 1.5 87 1 2
Overlaying the exposure, sensitivity and adaptive capacity maps, the overall climate change vulnerability map in
Cagayan Valley with the rice and corn farming systems resulted to the following: Echague, Isabela had the highest
land area with high vulnerability of 99,726.53 ha, followed by Penablanca with 22,872.85 ha, then by Maddela with
7,737.87 ha and Bagabag as the lowest with only 378.85 ha (Figure 11). For the four study sites, most of the land
area had low vulnerability with 298,862.93 ha, followed by moderately vulnerable with 176,250.34 ha while the
lowest was highly vulnerable with 130,716.10 ha.
Figure 11. Overall climate change vulnerability map
Farming systems in the study sites.
Based on the attributes of the layers, the exposure, sensitivity, adaptive capacity and overall climate change
vulnerability indices (Tables 2 - 5) of the rice and corn farming systems in the study sites were tabulated and ranked
as follows:
Table 2. Exposure index of rice and corn farming systems in the study sites.
Table 3. Sensitivity index of rice and corn farming systems in the study sites.
Table 4. Adaptive capacity index of rice and corn farming systems in the study sites.
Table 5. Overall climate change vulnerability of rice and corn farming systems in the study sites.
3.3 GIS-based Crop Suitability of Climate
Change-Resilient Tropical Fruits
3.3.1 Topographic Suitability: For topographic suitability combining elevation and slope as overlay factors, all the
tropical fruits (mango, pummelo, lanzones, rambutan and jackfruit) were within highly suitable topography (within
600 masl elevation and within 0-50% slope category). The eastern parts of Penablanca and Maddela which were the
mountain ranges of Sierra Madre are moderately suitable. Also the mountain ranges of Caraballo made some parts of
Bagabag and Maddela moderately suitable for the tropical fruits (Figure 12).
Figure 12. Topographic suitability of the study sites.
3.3.2 Soil Suitability: Overlaying the soil texture, soil pH and Land Use maps produced the soil suitability map
(Figure 13). Forests, built-up areas, aquatic areas and rivers were not suitable. Highly suitable areas were those that
have loam to clay loam soil and croplands mixed with brushlands and grasslands.
Figure 13. Soil and land use suitability of tropical fruits in the study sites.
3.3.3 Climate Suitability: Monthly temperature and rainfall were both suitable for tropical fruits considering
temperature and rainfall ranges of 24.3–27.2 oC and 465.7–657 mm, respectively. However, frequent occurrence and
tracks of typhoons in Cagayan Valley reduced suitability of tropical fruits (Figure 14).
Figure 14. Climate suitability of tropical fruits.
3.3.4 Overall Biophysical Suitability: Overlaying topographic, soil and climate suitability produced the following
overall biophysical suitability map (Figure 15).
Figure 15. Overall biophysical suitability of tropical fruits in the study sites.
4. CONCLUSION AND RECOMMENDATIONS
The monocrop corn farming systems in Penablanca, Cagayan and Echague, Isabela had the highest climate change
vulnerability index considering that the crop had higher exposure to multi-hazards, more areas with more farmers
affected, lower income, knowledge, perception and less access to land/water resources.
All the tropical fruits (rambutan, Guimaras Mango, lanzones, pummelo) and bamboo were suitable to be planted in all
the barangay study sites based on their basic ecological requirements: Elevation < 700 masl; Slope = 18-30%; Soil
texture= sandy clay-loam; Soil ph > 5; Gen. climate = pronounced; Rainfall > 1,000 mm/yr; and Temperature < 30oC.
The climate change vulnerability of major farming systems should be disseminated to farmers, communities and
LGUs and develop and formulate appropriate climate change adaptation plans for farming systems.
Hands-on training on GIS for LGUs should be conducted in order to utilize the geodatabase on crop suitability and
climate change vulnerability maps for climate change resilient-farming system planning and development.
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