Transcript Desertification a Challenge to the Horn of Africa

DESERTIFICATION A CHALLENGE TO THE HORN OF AFRICA: AN EXAMPLE OF THE AFAR RGION
Girma Taddese, [email protected] and Don Peden ,[email protected]
International Livestock Research Institute
P. O. Box 5689 Addis Ababa Ethiopia
INTORODUCTION
Figure 10. Wherever Awash River crosses there is life.
Manifestations of desertification include accelerated soil erosion by wind
and water, increasing salinization of soils and near-surface groundwater
supplies, a reduction in soil moisture retention, an increase in surface runoff
and stream flow variability, a reduction in species diversity and plant
biomass, and a reduction in the overall productivity in dry land ecosystems
with an attendant impoverishment of the human communities dependent on
these ecosystems. Additional impacts include an increase in particulate and
trace gas emissions from biomass burning in dry lands and an increase in
atmospheric dust loads.
Desertification can generally be defined as land degradation in arid, semiarid and dry sub-humid areas resulting mainly from adverse human impact
and climate variation. This phenomenon overlaps with a number of related
environmental issues such as climate change, population growth, trade and
biodiversity. There is also a complex cause-effect relationship between
desertification, population growth and poverty.
Observation Site
1. Udic SMR = Ppt > 1000 mm, AWC = 300-392 mm
2. Ustic SMR = Ppt = 700-1000 mm, AWC = 192-342 mm
3. Xeric SMR = Ppt = 300-700 mm, AWC = 50-198 mm
4. Aridic SMR = Ppt < 300 mm,
(SMR = Soil moisture regime, AWC = Available water holding capacity,
Ppt = Precipitation)
Figure 3. Soil moisture regime zones in Ethiopia (Source Hawando 1989).
Uses
1. Perennial and annual crops & forestry
2. Annual crops, perennial crops grazing forestry j
3. Rangelands, annual crops, irrigated farms
4. Rangelands, farms, sporadic annual crops
Constraints
Poor farming systems, deforestation, over grazing & population pressure
Poor farming system, deforestation, over grazing, population pressure & land degradation
Deforestation, over grazing, erosion, salinity, draught, erratic & low rainfall
Moisture deficit, wind erosion, drought, over grazing erratic and low rainfall, salinity
Lower Awash Valley (Afar Region)
1. Hyper-arid (PR/PET < 0.02)
3. Semi-arid (0.20  RR/PET < 0.5)
Figure 11. The last chance for extinction for this plant
species and complete desertification.
2. Arid (0.2  RR/PET  0.20)
4. Dry sub-humid (0.5  RR/PET< 0.65)
5. Humid (R/PET> 0.65)
Figure 4. Salt patches and and salt tolerant grass and
shrub species.
Figure 5. Salt and draught tolerant shrub species
staggering in extreme climatic conditions.
Figure 6. Draught and over grazing persistent shrub
and grass species in plain areas can survive
with little shower of rainfall.
Figure 7. Exposition of the slope type and erosion-draught
tolerant plant spices may some times help in
sand stabilization.
Figure 1. Dry land areas in Ethiopia delineated on the bases of
PR/PET ratio. (Source: Tamirie Hawando. 2001)
3000
2500
mm/year
2000
Figure 12. We can stop desertification if we really
understand the nature of arid land and
allow the community to care of their land.
1500
1000
500
0
425-3000
120-2700
625-2550
175-1000
Humid
(moist)
Dry subhumid
Semi-arid
Arid
0-660
Hyper-arid
Elivation (mm) at different ecological zones
Rainfall
Evaporation
Figure 2. Relationship between elevation, rainfall and evaporation.
Humid (moist)
Dry sub-humid
Semi-arid
Arid
Hyper-arid
Aridity index
1.25
0.60
0.38
0.12
0.03
Land area (km2 x 1000)
350
300
207
300
53
Figure 8. Aggressive Prosopis Juliflora species is salt and draught
tolerant, due to tough throne and alkaloid content it is not
preferred by livestock (Girma Taddese and Shimelis Taddese.
1996. Julifolora Reclaims wasteland in Middle Awash Valley.
IAR News of Agricultural Research. Vol. 11 No. 2).
Figure 9. Dead land with out vegetation of higher order.
Figure 13. Research and Development is needed to
understand this draught- salt tolerant and
wind persistent multi purpose plant species.