Presiding Officer Training module 2024 lok sabha elections
Cn 2 th14_inida_assessment of land degradation_baptista
1. Assessment of land degradation
indicators in an insular sahelian
mountain region – case study of
the“Ribeira Seca” watershed
J. Tavares; I. Baptista; A.Ferreira; L.Varela; J. Bentub
and COA Coelho
2. Content
• Introduction (background and justification
and objectives)
• Country data
• Factors contributing to land degradation
• Soil and water conservation techniques
• Materials and method
– The study site
– Methodology
• Results and discussion
• Conclusion
3. Introduction • Cape Verde, as a sahelian
country, has been severely
affected by the desertification
phenomenon, although extreme
efforts are being made to
reverse the process
• Desertification is a major issue in
Cape Verde and directly
influences the livelihoods of local
farmers
• Several techniques were
implemented throughout the last
decades to halt the
desertification process
– Efficiency has hardly been accessed.
4. Introduction • To combat desertification,
integrated approaches are to
be sought, combining social and
biophysical viewpoints, and
linking local and scientific
knowledge
• The first step is to assess the
problem using an integrated
approach, to identify variability
and worst cases, as basis of
strategy and actions to be
defined
• Indicators are very useful in
this context
5. Indicators
• Environmental and socio-economic indicators play an
increasingly important role in supporting development
policies for combating desertification
• An indicator is a measurement that reflects the
status of social, economic or environmental systems
• They can be used to track changes in complex
systems and monitor progress towards pre-
determined goals
• Their role is to simplify the complex interrelations of
the socio-economic and environmental reality and
convey them in an unambiguous way
6. Some country data
• Location: West African coast
• Surface area: 4033 km2
• Composed of 10 islands and 5 islets
• Population: 430 000
• Arable land: 10% of total land area (42000 ha)
• Dryland agriculture: 38 000 ha (>90%)
• Irrigated land: 3000-5000 ha (<5.0%)
• Climate: dry tropical w/2 distinct seasons: dry season (November to
June) and the rainy season (July to October)
• Mean annual rainfall: 230 mm with great spatial-temporal variability
• Terrain: steep, rugged, rocky and volcanic
• Contribution of agriculture to GDP: 12 %
7. Objectives
• Goal: To improve the knowledge on
desertification risks related with land use
• Specific objectives:
1. assess the indicators applied in the various
land use type
2. analyze the main drivers of desertification and
their impact on social, economic, natural
capital, ecological and economic functions
8. Factors contributing to land
degradation
• Heavy rainfall events ⇒ Flash floods (Soil erosion by
water)
• Low, insufficient and irregular rainfall (space and time)
• Frequent droughts
• Soil fertility decline (no nutrient replenishment)
• Low soil OM content
• Cultivation of very steep slopes
• Inadequate rain-fed farming practices
• Overexploitation of ground water ⇒ Water and soil
salinization
Land degradation and desertification
9. Soil and water conservation
techniques
• To deal with land degradation (erosion and
drought), CV governments have implemented
several SWC techniques
– in field (mechanical and biological structures)
• Terraces, stone walls, contour ridges
• Vegetation live barriers (green belts)
– off field
• water harvesting (large dams, reservoirs, etc)
• check dams, etc.)
10. Contour ridges combined
with leucaena leucocephala
Contour stone wall combined w/
agroforestry species
Contour stone walls combined
w/ Furcraea gigantean
Stone walls combined with
aloe vera
11. • Contour stone walls in corn/bean production
system (left)
• Terraces built on slope, planted with rainfed crops -
corn & beans (right)
12. Contour ridges on very steep
slope for peanut production
in-field (contour stone wall w/
vegetation barrier) and off-field
(check dams) SWC techniques
contour stone wall
Aloe vera barriers
16. Study site characteristics
• Location: East-central side of
the Santiago island
• Population: 14 343
• Main activity: agriculture
• Drainage area: 71.50km2
• Land use: 83% rainfed
agriculture; 5 % irrigated land;
4% forest; 1% rock outcrop; 7%
other
• 4 bioclimatic zones: 11%
humid; 20% sub humid; 49%
semiarid; 20% arid
• Main dryland crops: maize and
beans
• Irrigated crops: banana,
sugarcane, roots and tubers
and vegetables
• Average slope: 8.6%
17. The study site: Physiographic indices
Sub basin /
basin
Area Length
river
Alt.
max
Alt. min Gravelius
Index (Kc)
Shape
form
(Kf)
River
slope
Basin
slope
Km2
Km m m - - % %
Longueira 4,18 3,45 1126 239 1,31 0,35 26 33,0
Grande 4,86 4,98 750 130 1,33 0,20 12,4 15,9
Godim 5,01 5,30 570 145 1,37 0,20 8,5 24,0
Seca 24,94 18,0 642 0 2,47 0,07 7,2 6,3
Ribeira Seca 71,50 18 1394 0 1,31 0,22 7,20 8,60
18. Methodology
• 103 points were surveyed in the
watershed following WB2
methodology
• The indicators used are based in
the DPSIR framework
• Classes were assigned using
existing classification systems
such as the European geo-
referenced soil data base, or
existing research data
• The various classes of indicators
were organized according to the
importance to land degradation
and desertification risk
DRIVER
S
Efficiency/Descr
iptive Indicators
Performance
Indicators
RESPONSES
Risk
Assessment
PRESSURES
Descriptive
Indicators
STATE
IMPACTS
Descriptive
Indicators
DPSIR elements and related indicators
24. Desertification risk map
• Almost 90 % of the
study area is sensitive
to desertification
• This situation reflects
the particular geo-
morphological
characteristics of the
watershed: low lands,
high population
density, and lack of
soil cover
25. Conclusion
• The indicators used to assess the desertification risk
at the Ribeira Seca catchment revealed to be a very
practical and useful tool:
– Allowing direct comparison between different
realities, rank the desertification risk,
– Identifying the more detrimental practices and
– Pinpointing the locations at higher risk of
desertification
• They allow perception of different realities within a
same area, and to evaluate the performance of
different conservation strategies, practices and
techniques.
