1. Chapter 5
THE CLIMATE OF ETHIOPIA AND THE
HORN
Ethiopia is characterized by a wide variety of altitudinal
ranges and diverse climatic conditions.
because of its closeness to the equator and the Indian
Ocean, the country is subjected to large temporal and
spatial variations in elements of weather and climate.
1
2. …cont’d
The climate of Ethiopia is therefore mainly controlled by the
1. Seasonal migration of the Intertropical Convergence Zone
(ITCZ) and associated atmospheric circulations
2. The complex topography of the country
Weather is the rapid or current state of the atmosphere
composing temperature, atmospheric pressure, humidity, wind
speed and direction, cloudiness and precipitation.
2
3. …cont’d
Climate refers the state of the atmosphere over long periods of
time, decades and more.
It is the composite of daily weather conditions recorded for long
periods of time. Averagly 30 years
Climate also takes into account the extremes or variations that
may occur beyond the average conditions.
3
4. 5.2. Elements and Controls of Weather and Climate
All weather conditions may be traced to the effect of the Sun on
the Earth.
Most changes in weather involve large scale horizontal motion
of air which is called wind.
Weather is expressed by a combination of several elements.
The climate of a region is ultimately determined by the
radiation, its distribution and temporal fluctuations.
4
5. Table 5.1. Elements and controls of weather and
climate
5.2.1. Controls of Weather and Climate
The climate of any particular location on earth is determined by
a combination of many interacting factors.
5
6. …cont’d
These include latitude, elevation, nearby water, ocean
currents, topography, vegetation, and prevailing
winds.
Hotness or coldness, rainy or cloudiness, sunniness,
windiness or calmness, of air you are feeling on the
daily base in your current location are expressions of
weather
6
7. …cont’d
Controls of weather and climate
Climatic controls :
A. Latitude
Latitude is the distance of a location from the equator.
The sun shines directly on equator for more hours during the year than
any where else.
As you move further away from the equator towards the poles, less
solar insolation is received during the year and the temperature become
colder.
Ethiopia’s latitudinal location has bearings on its temperature
7
8. …cont’d
Latitudinal location of Ethiopia and the Horn resulted in:-
High average temperatures,
High daily and small annual ranges of temperature,
No significant variation in length of day and night between
summer and winter.
B. Inclination of the Earth's Axis
8
9. …cont’d
The Earth's rotation axis makes an angle of about 66 ½ ° with the
plane of its orbit around the sun, or about 23 ½ ° from the
perpendicular to the ecliptic plane
This inclination determines the location of the Tropics of Cancer,
Capricorn and the Arctic and Antarctic Circles.
As the earth revolves around the sun, this inclination produces a
change in the directness of the sun's rays;
which in turn causes the directness of the sun and
differences in length of day and seasons.
9
10. Equinoxes and Solstices .
An equinox is the instant of time when the sun strikes the plane of
the Earth's equator.
During this passage the length of day and night are equal.
Equinox appears twice a year. Let's see two major equinoxes
1. The Vernal (spring) equinox:-
is the day when the point of verticality of sun’s rays crosses the
equator Northwards
This equinox experiences in Northern Hemisphere when the sun is
exactly above the equator.
10
12. …cont’d
Vernal (spring) equinox marks the beginning of spring season.
March 21 marks the offset of the vernal equinox.
2. The Autumn equinox:
appears to happen when the sun crosses equator giving
approximately equal length between day and night.
It appears to happen when the visible sun moves south across the
celestial equator on 23rd of September.
It marks the beginning of Autumn season.
12
13. …cont’d
Solstice is an event when the overhead sun appears to
cross northern or southern points relative to the
celestial equator resulting in unequal length of days and
nights in the hemispheres.
1.The summer Solstice:
on June 21st, the northern hemisphere has maximum
tilt towards the sun experiencing longest daylight of the
year.
13
14. …cont’d
It is the astronomical first day of summer in the Northern Hemisphere.
The sun is at its highest position in the noonday sky, directly above
23 ½ in the Tropic of Cancer.
2. The winter solstice:
22nd of December is the day when the maximum southward
inclination is attained in the Southern Hemisphere.
In this event the sun travels shortest length causing longest night and
shortest daylight. In the Northern Hemisphere, it occurs when the sun
is directly over the Tropic of Capricorn, which is located at 23 ½ °
south of the equator.
14
15. …cont’d
c.Altitude
Altitude is the height of location above the sea level.
Under normal conditions there is a general decrease in
temperature with increasing elevation.
The average rate at which temperature changes per unit of
altitudinal change is known as lapse rate.
The lapse rate is limited to the lower layer of the atmosphere
named as troposphere.
The normal lapse rate is 6.5°C per kilometer rise in altitude.
15
16. …cont’d.
Atmosphere extends to
32,000 km (20,000mi)
from surface
Exosphere’s top is at
480 km (300 mi)
The atmosphere is
structured. Three
criteria to examine
atmosphere
Composition
Temperature
Function
16
17. Types of lapse rate
Three types of lapse rates are identified:-
1.Dry adiabatic laps rate
The temperature changes occurring in the rising or subsiding air
mass are not the result of additions of heat to, or withdrawals of heat
from outside sources, but rather are the consequence of internal
processes of expansion and contraction. This is known as adiabatic
temperature change.
An adiabatic lapse rate -is the rate at which the temperature of an
air parcel changes in response to the expansion or compression
process associated with a change in altitude.
17
18. …cont’d
Ascending motion: the parcel
of air expands, does work
on the rest of the
atmosphere and cools down
Descending motion: the air
parcel compresses, work is
done on the air parcel and it
warms up
Adiabatic process: no heat
is exchanged between the
air parcel and the rest of the
atmosphere
18
19. …cont’d
. When air rises, it expands because there is less weight of air
upon it
if a mass of dry air at sea level rises to an altitude of about
18,000ft (5486.22 meters), the pressure upon it is reduced by
nearly half and consequently its volume is doubled.
More precisely, if the upward movement of air does not produce
condensation, then the energy expended by expansion will cause
the temperature of the mass to fall at the constant dry adiabatic
lapse rate.
The rate of heating or cooling is about 10°C for every 1000 m of
change in elevation.
This rate applies only to unsaturated air, and thus it is called the
dry adiabatic laps rate.
19
20. …cont’d
Vertical displacements of air are the major cause of adiabatic
temperature change
2 . Wet Adiabatic laps rate
Due to the fact that the heat added during condensation starts
cooling following the expansion, the air will no longer cool at the
dry adiabatic rate.
This is due to the latent heat in the water vapor carried by the air.
The heat is released in the process of ascent, therefore affecting
or lowering the rate of temperature change of the rising air.
saturated air containing water droplets were to sink, it would
compress and warm at the moist adiabatic rate.
20
21. …cont’d
The rate at which rising or sinking saturated air changes its
temperature is less than the dry adiabatic rate.
Prolonged cooling of air invariably produces condensation,
thereby liberating latent heat.
Therefore, rising and saturated or precipitating air cools at a
slower rate than air that is unsaturated.
This process is called wet adiabatic temperature change. The rate
of cooling of wet air is approximately 5 c per 1000 meters ascend.
21
22. 3. Environmental lapse rate or Atmospheric lapse late
This refers to the actual, observed change of temperature with
altitude
The fact that air temperature is normally highest at low elevations
next to the earth and decreases with altitude
clearly indicates that most of the atmospheric heat is received
directly from the earth's surface and only indirectly from the sun.
But the lower layer is warmer, not only because it is closest to the
direct source of heat but also b /c of its high density.
It contains more water vapor and dust, which causes it to be a
more efficient absorber of earth radiation than is the thinner, drier,
cleaner air aloft.
22
23. …cont’d
This decrease in temperature upward from the earth's surface
normally prevails throughout the lower atmosphere called
troposphere.
The principal exception to the rule is the cause of temperature
inversions. The rate of change is 6.5 C/1000 meters.
23
24. Adiabatic lapse rate:
the rate of change of the
temperature of a rising (sinking)
air parcel with altitude as a result
of adiabatic expansion .
(compression) .
. Dry adiabatic lapse rate: the
air parcel is unsaturated
(RH<100%),
(otherwise condensation,
latent heat, see below)
For the Earth: 10 deg C/km.
For Jupiter: 2 deg C/km.
Environmental lapse rate: the
actual rate of change of the
temperature with height.
24
25. 5.3. Spatiotemporal Patterns and Distribution of
Temperature and Rainfall in Ethiopia
5.3.1. Spatiotemporal Distribution of Temperature
Altitude is an important element in determining temperature of
Ethiopia and the Horn.
Latitude, humidity and winds, with varying magnitude have also
significant impacts on temperature conditions in Ethiopia.
The spatial distribution of temperature in Ethiopia is primarily
determined by altitude and latitude
The location of Ethiopia at close proximity to equator, a zone of
maximum insolation, resulted for every part of the country to
experience overhead sun twice a year.
However, in Ethiopia, as it is a highland country, tropical
temperature conditions have no full spatial coverage. They are
limited to the lowlands in the peripheries.
25
26. …cont’d
Mean annual temperature varies from over 30 degree C in the
tropical lowlands to less than 10 degree c at very high altitudes
the Bale Mountains are among highlands where lowest mean
annual temperatures are recorded.
The highest mean maximum temperature in the country is
recorded in the Afar Depression.
Moreover, lowlands of north-western, western and south-
eastern Ethiopian experiences mean maximum temperatures of
more than 30 degree C.
26
28. …cont’d
The major controls determining temperature distributions are
latitude and cloud cover. However, some parts of the country
enjoy a temperate climate.
In the tropics, the daily range of temperature is higher and the
annual range is small, whereas the reverse is true in the
temperate latitudes. In Ethiopia, as in all
places in the tropics, the air is frost free and changes in solar
angles are small making intense solar radiation.
28
29. …cont’d
Ethiopia’s daily temperatures are more extreme than its annual
averages.
Daily maximum temperature varies from a high of more than 37
58 degree C over the lowlands in northeast and southeast to a low
of about 10 degree C-15 C over the northwestern and southwestern
highlands.
in the case of monthly averages, variation is minimal and the annual
range of temperature is small true in both the highlands and lowlands
In Ethiopia and elsewhere in the Horn, temperature shows seasonal
variations.
For example, months from March to June in Ethiopia have records of
highest temperatures. Conversely, low temperatures are recorded from
November to February.
29
30. …cont’d
Southern part of Ethiopia receives highest records of
temperature in autumn and spring following the relative shift of
the sun; whereas in the northern part of the country, summer
season is characterized by higher temperature.
Unlike other parts of Ethiopia, the southern and southwestern
highlands experience reduced temperature.
This is because the temperature and the amount of energy
reaching the surface is directly related with the directness of the
sun.
30
31. 5.3.2. Spatiotemporal Distribution of Rainfall
. Rainfall system in Ethiopia is characterized by complexities. To
encompass the system, it needs an understanding of the position of
Inter Tropical Convergence Zone (ITC), pressure cells, and
Trade Winds.
the rainfall system in Ethiopia is characterized by spatial and
temporal variabilities.
Rainfall in Ethiopia is the result is influenced by the position of
Intertropical Convergence Zone (ITCZ).
The convergence of Northeast Trade winds and the Equatorial
Westerlies forms the ITCZ, which is a low-pressure zone.
31
33. …cont’d
The inter-annual oscillation of the surface position of the ITCZ
causes a variation in the Wind flow patterns over Ethiopia and
the Horn.
Following the position of the overhead sun, the ITCZ shifts
north and south of the equator.
As the shift takes place, equatorial westerlies from the south and
southwest invade most parts of Ethiopia bringing moist winds.
The ITCZ shifts towards south of equator (Tropic of Capricorn)
in January.
During this period, the Northeast Trade Winds carrying non-
moisture-laden dominates the region.
Afar and parts of Eritrean coastal areas experience rainfall in this
period.
33
34. …cont’d
Following the directness of the Sun in March and September
around the equator, the ITCZ shifts towards equator.
During this time, the central highlands, southeastern highlands and
lowlands receives rainfall as the south easterlies bring moist winds.
Seasonal or Temporal Variabilities
What winds bring summer rainfall for Ethiopian highlands?
The seasonal and annual rainfall variations are results of the
macro-scale pressure systems and monsoon flows which are
related to the changes in the pressure systems
34
35. The temporal variabilities of rainfall are characterized
by;
1. Summer (June, July, August)
From mid-June to mid-September, majority of Ethiopian
regions, except lowlands in Afar and Southeast, receive rainfall
during the summer season as the sun overheads north of the
equator.
High pressure cells develop on the Atlantic and Indian Oceans
around the tropic of Capricorn although the Atlantic
contributes a lot, the Indian Ocean is also source of rainfall.
35
36. …cont’d
During this season, Ethiopia and the Horn come under the
influence of the Equatorial Westerlies (Guinea monsoon) and
Easterlies
ii. Autumn (September, October and November)
Autumn is the season of the year between summer and winter
The exact position of the ITCZ changes over the course of the
year, oscillating across the equator
36
37. …cont’d
In autumn the ITCZ shifts towards the equator weakening the
equatorial westerlies.
During this season, the south easterlies from Indian Ocean
showers the lowlands in southeastern part of Ethiopia.
iii. Winter (December, January and February)
In winter, the overhead sun is far south of equator. During this
season, northeasterly winds originating from the landmass of
Asia dominantly prevail Ethiopian landmass
37
38. …cont’d
The northeasterly winds crossing the Red Sea carry very little
moisture and supplies rain only to the Afar lowlands and the Red
Sea coastal areas.
iv. Spring (March, April and May)
In this season, the noonday sun is shining directly on the equator
while shifting north from south.
The shift of the ITCZ, results in longer days and more direct
solar radiation providing warmer weather for the northern
world.
38
39. …cont’d
the effect of the northeast trade wind is very much reduced.
the southeasterlies from the Indian Ocean provide rain to
the highlands of Somalia, and to the central and
southeastern lowlands and highlands of Ethiopia.
Rainfall Regions of Ethiopia
Based on rainfall distribution, both in space and time, four
rainfall regions can be identified in Ethiopia and the Horn.
These are:
39
40. …cont’d
1. Summer rainfall region
This region comprises almost all parts of the country, except the
southeastern and northeastern lowlands.
The region is divided in to dry and wet summer rainfall regions.
Hence, the wet corresponds to the area having rainfall of 1,000 mm or
more
2. All year-round rainfall region
It has many rainy days than any part of the country. It is a rainfall
region in the southwestern part of the country.
40
41. …cont’d
Both duration and amount of rainfall decreases as we move from
southwest to north and eastwards.
Months in summer gain highest rainfall whereas the winter
months receive the reduced amount.
The average rainfall in the region varies from 1,400 to over 2,200
mm/year.
iii. Autumn and Spring rainfall regions
The region comprises areas receiving rain following the influence
of southeasterly winds
41
42. …cont’d
South eastern lowlands of Ethiopia receive rain during autumn
and spring seasons when both the north easterlies and equatorial
westerlies are weak
The south-easterlies bring rainfall from the Indian Ocean.
About 60 percent of the rain is in autumn and 40 percent in spring.
The average rainfall varies from less than 500 to 1,000 mm
42
43. …cont’d
iv. Winter rainfall region
This rainfall region receives rain from the northeasterly winds.
During the winter season, the Red sea escarpments and some parts of the
Afar region receive their main rain.
5.4 Agro-ecological Zones of Ethiopia
As a result of the diversified altitude and climatic conditions, Ethiopia
possesses diverse agro climatic zones.
43
44. …cont’d
These zones have traditionally been defined in terms of
temperature
This system divides the nation into five major climatic zones
namely Bereha, Kolla, Woina Dega, Dega and Wurch
The Wurch Zone
The Wurch-zone is an area having altitude higher than
3,200 meters above sea level and mean annual temperature
of less than 10°C
44
45. …cont’d
Mountains having typically fitting characteristics of this zone
include mountain systems of Ras Dashen, Guna, Megezez in North
Shoa, Batu, Choke, Abune Yoseph etc.
45
46. …cont’d
Dega Zone
This is a zone of highlands having relatively higher temperature
and lower altitude compared to the wurch Zones.
In Ethiopia, the Dega-zone is long inhabited and has dense
human settlement due to reliable rainfall for agriculture and
absence of vector-borne diseases such as malaria.
Weyna Dega Zone
This zone has warmer temperature and moderate rainfall.
It lies between 1500-2,300 meters above sea level.
It is the second largest zone covering more than 26% of the
landmass of Ethiopia.
46
47. …cont’d
The temperature and rainfall of this category is highly
suitable for majority of crops grown in Ethiopia
Hence, the zone includes most of the agricultural land.
The Weyna Dega zone has also two growing seasons.
Kolla Zone
In Ethiopia, the geographic peripheries in south,
southeast, west and northeastern part are mainly in this
category.
47
48. …cont’d
Kolla is the climate of the hot lowlands with an altitudinal
range of 500 to 1500 meters above sea level.
Average annual temperature ranges between 20°C and 30°C.
Although mean annual rainfall is erratic (changeable), it
can be as high as 1500 mm in the wet western lowlands of
Gambella.
Rainfall is highly variable from year to year. The region is
boundary between the hot arid (Bereha) and the humid
climates (Woina Dega).
48
49. …cont’d
Bereha Zone
Bereha is the hot arid climate of the desert lowlands.
The Bereha agro-climatic zone is largely confined to lowland areas with
altitude of lower than 500 meters.
Around Danakil depression, the elevation goes below the sea level.
Its average annual rainfall is less than 200 mm, and average
annual temperature is over 27.5oC. Strong wind, high temperature,
low relative humidity, and little cloud cover usually characterize
Bereha.
49
50. …cont’d
Evapotranspiration is always in excess of rainfall. Djibouti,
majority of Somalia, and coastal areas of Eritrea are categorized
under Kolla and Bereha zones.
50
52. 5.5. Climate Change/Global Warming: Causes, Consequences
and Response Mechanisms
Climate change refers to a change in the state of the climate that
can be identified (e.g. using statistical tests) by changes in the
mean and/or the variability of its properties and that persists for an
extended period, typically decades or longer.
It refers to any change in climate over time, due to either
natural variability or human activities.
5.5.1. Current Trends of Climate in Ethiopia
Besides spatial and temporal variations in different parts of the
country, Ethiopian climate experiences extremes such as drought,
flood etc.
52
53. …cont’d
Ethiopia ranked 5th out of 184 countries in terms of its risk of
drought.
In the country, 12 extreme drought events were recorded
between 1900 and 2010.
Among the 12, seven of the drought events occurred since 1980.
The majority of these resulted in famines.
The severe drought of 2015-2016 was exacerbated by the
strongest El Nino that caused successive harvest failures and
widespread livestock deaths in some regions
53
54. Trends in Temperature Variability
Over the last decades, Ethiopia has experienced climatic
changes.
Mean annual temperature has shown 0.2°C to 0.28°C rise per
decade over the last 40- 50 years.
A rise in average temperature of about 1.3°C has been observed
between 1960 and 2006.
The rise has spatial and temporal variation.
Higher rise in temperature was noted in drier areas in northeast
and southeast part of the country.
54
55. …cont’d
Higher rise in temperature was noted in drier areas in northeast
and southeast part of the country.
Notably the variability is higher in July-September.
The number of ‘hot days’ and ‘hot nights’ has also shown
increment. Consequently, the country’s minimum temperature has
increased with 0.37°C to 0.4°C per decade.
55
57. Trends in Rainfall Variability
Precipitation has remained fairly stable over the last 50 years when
averaged over the country.
However, these averages do not reflect local conditions which are
extremely divergent and the natural variability in rainfall in the country
makes it difficult to detect longterm trends.
Rainfall variability is increasing (and predictability is decreasing) in
many parts of the country. In some regions, total average rainfall is
showing decline.
57
58. …cont’d
This has strong implications for crop production, which becomes
clear when assessing the change in areas that receive sufficient rain
to support crop production.
Changes in temperature and rainfall increase the frequency and
severity of extreme events.
Major floods have been a common occurrence, leading to loss of
life and property in numerous parts of the country.
58
59. …cont’d
5.5.2. Causes of Climate Change
The causes of climate change are generally categorized as Natural
causes and anthropogenic/manmade causes.
A. Natural Causes
Climate change has many natural causes, such as variations in the
energy budget, the position of Earth relative to Sun, the
position of continents relative to the equator, and even whether
the continents are together or apart.
Here are some of the major natural causes:
59
60. …cont’d
Here are some of the major natural causes
Earth orbital changes (More tilt means warmer summers and colder
winters)
Energy Budget
Volcanic eruptions:(volcanic eruption releases large volumes of
sulphur dioxide, carbon dioxide, water vapor, dust, and ash into the
atmosphere).
B. Anthropogenic Causes
The growing influence of human activities on the environment
60
61. …cont’d
global warming caused by such anthropogenic effects is growing.
The warming of earth planet in the past 50 years is majorly
driven by human activities.
Human induced greenhouse gases such as carbon dioxide,
methane and nitrous oxide have caused much of the observed
increase in Earth's temperatures over the past 50 years.
The major gases that contribute to the greenhouse effect include
Water vapor, Carbon dioxide (CO2), Methane, Nitrous oxide,
Chlorofluorocarbons (CFCs)
61
62. …cont’d
Although, methane is less abundant in atmosphere, it is by far
more active greenhouse gas than carbon dioxide.
5.5.3. Consequences of Climate Change
Caused loss of life, damaging property and affecting livelihoods
Higher impact in low income countries, since they have limited
capacity to cope with the changes.
62
63. …cont’d
Impacts on human health
Impact on water resources:(snow and glaciers that increases rise in sea
level, increase drought and floods, distorts wind flow pattern, decreases
water table
Impact on Agriculture
Impact on Ecosystem:
5.5.4. Climate Response Mechanism
A. Mitigation and its Strategies
• reduce and control greenhouse gas emissions changing the climate.
63
64. …cont’d
There are some mitigation measures that can be taken to avoid
the increase of pollutant emissions.
Practice Energy efficiency
Increase the use of renewable energy such as solar
Efficient means of transport
implementation: electric public transport, bicycle, shared cars etc.
B. Adaptation and its Strategies
adjusted to and coped with changes in climate and extremes with
varying degrees of success.
64
65. …cont’d
adapting to life in a changing climate.
adjusting to actual or expected future climate
reduce our vulnerability to the harmful effects of climate change
such as extreme weather events or food insecurity
Some of the major adaptation strategies include:
building flood defenses,
plan for heat waves and higher temperatures,
installing water-permeable pavements to better deal with floods
and storm water
65
66. …cont’d
landscape restoration and reforestation,
flexible and diverse cultivation to be prepared for natural
catastrophes
preventive and precautionary measures (evacuation plans, health
issues, etc.)
improve water storage and use are some of measures taken by
cities and towns
66
67. Chapter 6
SOILS, NATURAL VEGETATION AND WILDLIFE
RESOURCES OF ETHIOPIA AND THE HORN
The past geological process and varied climatic events ensued Ethiopia
to have varied soil and biological diversity.
The formation and spatial variabilities of soils in Ethiopia is largely
related to topographic and climatic factors, parent material (rocks) and
land use.
Ethiopia possess unique characteristic fauna and flora with a high
level of endemicity.
67
68. 6.2. Ethiopian Soils Types, Degradation and Conservation
Soil is a delicate but highly varied composition of mineral
particles, organic matter and living organisms in dynamic
equilibrium.
Soil formation is a long-term process.
The formation of a particular type of soil depends on parent
material, climate, topography, living organism and time
Weathering disintegrates the inorganic substances (rocks) of soils.
68
69. …cont’d
There are three types of weathering involving in soil formation.
These are:
A.Mechanical (physical) weathering
Physical disintegration causes decrease in size without
appreciably altering composition
Abrasion (erosion by friction) due to water containing sediment or
wind carrying debris is another type of physical weathering
69
70. …cont’d
B. Biological weathering
The process of biological weathering involves the weakening and
subsequent disintegration of rock by plants, animals and microbes.
Roots of plant can exert pressure on rock
C. Chemical weathering
the modification of the chemical and mineralogical composition of
the weathered material.
A number of different processes can result in chemical weathering.
70
71. …cont’d
the most common chemical weathering processes are hydrolysis,
oxidation, reduction, hydration, carbonation, and solution.
In most cases, the minerals in the parent materials are also found in the
soils, which are formed from the disintegration and decomposition of the
rock
Soils have two basic properties;
1. Physical properties
composition and proportion of major soil components.
Properties such as texture, structure, porosity etc.
71
72. …cont’d
2. Chemical Properties
Soil chemistry is the interaction of various chemical constituents
that takes place among soil particles and in the water retained by
soil.
Soil properties like availability of minerals, electrical
conductivity, soil pH, etc.
Soil chemical properties affect soil biological activity and
indirectly the nutrient dynamics.
72
composition and proportion of major
soil components. Properties such as
texture, structure, porosity et
composition and proportion of major
soil components. Properties such as
texture, structure, porosity et
73. 6.2.2. Major Soil Types in Ethiopia
Soils of Ethiopia are basically derived from crystalline, volcanic
and Mesozoic sedimentary rocks.
soil divisions in the country are based on the geologic structure.
FAO has identified 18 soil associations in Ethiopia at scale of
1:2,000,000.
Out of the major soils, 11 soil associations cover about 87.4
percent of the land area. The six major groups of soils are
identified in Ethiopia based up on:
73
74. …cont’d
The six major groups of soils are identified in Ethiopia based up on:
A. Environmental condition i.e. parent material, climatic conditions,
topography, the way they were formed.
B. Characteristic i.e. significant chemical and physical properties.
C. Agricultural suitability in relation to texture, structure,
topography, moisture-storage capacity, etc.
D. Occurrence: general location of the soil types.
74
75. …cont’d
1. Nitosols and Acrisols
Nitosols develop on gently sloping ground.
Their parent materials include trap series volcanics, volcanic ash,
and even metamorphic rocks.
They are strongly weathered soils but far more productive than
most other tropical soils.
They are basically associated with highlands with high rainfall and
they were, probably, formed on forest covered areas originally.
75
76. …cont’d
There is considerable soil leaching which makes the nitosols to
be poor in soluble minerals like potassium, calcium etc.; and
rich in non-soluble minerals like iron and aluminum.
The reddish-brown color of these soils is because of high
concentration of iron (ferric) oxides due to leaching.
But they are now widely found on cultivated areas and on
mountain grasslands.
Nitosols are dominantly found in western highlands (Wellega),
southwestern highland (Kaffa, Illuababora), Southern highlands,
Central highlands, and Eastern highlands.
76
77. …cont’d
Acrisols ; are one of the most inherently infertile soils of the tropics,
becoming degraded chemically and organically very quickly when
utilized.
Acrisols have very low resilience to degradation and moderate
sensitivity to yield decline.
In Ethiopia, it has lost most of the base nutrients and are
characterized by low productive capacity.
Acrisols are found along with nitosols mostly in some pockets of
southwestern highlands of Ethiopia where there is high rainfall.
77
78. …cont’d
2. Vertisols
are heavy clay soils with a high proportion of swelling clays when
wet, and cracks when dry.
These soils are extremely difficult to manage (hence easily
degraded), but has very high natural chemical fertility.
Vertisols mostly develop on volcanic plateau basalt, trachyte and
pyroclastic materials, sedimentary rocks, colluvial slopes and alluvial
plains.
78
79. …cont’d
The vertisols are also soils of highlands and moderate climates.
In Ethiopia, they are commonly found in parts of Northwestern,
Central and Southeastern highlands (especially in Gojjam, Shewa,
Arsi, Bale and central Hararghe)
3. Lithosols, Cambisols and Regosol
found in rugged topography and steep slopes.
There is little evidence of pedogenic processes (soil forming
processes).
they are young, shallow and coarse textured and so have low
water holding capacity
found in areas of low rainfall.
79
80. …cont’d
most of the areas covered by these soils have limited agricultural
use.
in most cases, left under the natural plant cover and used for
grazing.
found in rugged and steep slopes of Central Highlands, on the
Rift Valley Escarpments and highlands in of western Hararghe
Regosol and Lithosols are also found in the Danakil and eastern
Ogaden.
80
81. …cont’d
4. Xerosols, Yermosols and Solanchaks
desert or dry steppe soils majorly available in arid and semiarid
areas.
high salt content and low organic content, because of the scanty
vegetation.
but are rich in phosphorus and potash and can be very fertile if
irrigated.
Xerosols are soils of the deserts, has low organic content.
Yermosols are even drier and more problematic than Xerosols.
81
82. …cont’d
Solanchaks are saline soils which develop in areas of high
evaporation and capillary action
Badly managed irrigation schemes may turn soils into
solonchaks
In Ethiopia, Xerosols are found in Ogaden and northeastern
escarpments, whereas the Yermosols and Solonchaks cover the
Ogaden and Afar plains.
The Solonchaks are majorly located in salty plains of Afar
82
83. …cont’d
5. Fluvisols
Fluvisols -These soils are associated with fluvial (river), marine
(sea) and lacustine (lake) deposits
fluvisols develop on flat or nearly flat ground, on recent alluvial
deposits.
These are soils formed due to deposition of eroded materials from
highlands.
The deposition takes place in depressions, lower valleys and
lowlands.
83
84. …cont’d
Lower regions of rivers like Omo, Awash, Abay and the plains of
Akobo and Baro Rivers are home for fluvivsols.
Lakes region (main Ethiopian rift) is also characterized by fluvisols.
Fluvisols are highly variable, but much prized for intensive
agriculture because:
they develop on flat ground, deposition sites,
they are associated with rivers and ground water, making them
important for largescale irrigation and
84
85. …cont’d
6. Luvisols
Luvisols develop mainly in areas where pronounced wet and dry
seasons occur in alternation.
Where leaching is not very high, they are found in association
with nitosols.
Luvisols have good chemical nutrients and they are among the best
agricultural soils in the tropics. So, they are intensively cultivated.
85
86. …cont’d
However, when luvisols are found on steep slopes (stony) and on flat
areas (waterlogged) they are avoided and left for grazing.
In Ethiopia, places with luvisols include Lake Tana area, parts of
Northern, Central and Eastern Highlands and Southern lowlands.
6.2.2. Soil Degradation
Soil degradation is defined as a change in any or all of soil status
resulting in a diminished capacity of the ecosystem to provide
goods and services.
86
87. …cont’d
deterioration of the physical, chemical and biological properties of
soil.
It is a major concern for at least two reasons.
First, soil degradation undermines the productive capacity of an
ecosystem.
Second, it affects global climate through alterations in water and
energy balances and disruptions in cycles of carbon, nitrogen,
sulfur, and other element
87
88. …cont’d
There are three major types of soil degradation.
1.Physical Degradation: refers to the deterioration of the physical
properties of soil. This includes:
A.Compaction:
B.Soil erosion; detachment of individual soil particles, transportation
and deposition
rain droplets considerably weakness the soil and makes susceptible
to erosion.
the soil will begin to move towards lower slope until the erosive
agent loses its energy.
In Ethiopia, an estimated average of 42 tons per hectare of soils
is eroded annually
88
89. …cont’d
ii. Biological Degradation
Reduction in soil organic matter content, decline in biomass
carbon, and decrease in activity and diversity of soil fauna are
ramifications of biological degradation.
Because of prevailing high soil and air temperatures, biological
degradation of soil is more severe in the tropics than in the
temperate zone.
It can also be caused by indiscriminate and excessive use of
chemicals and soil pollutants.
89
90. …cont’d
iii. Chemical Degradation
Nutrient depletion is a major cause of chemical degradation.
In addition, excessive leaching of cat-ions in soils with low-
activity clays causes a decline in soil pH and a reduction in base
saturation.
Chemical degradation is also caused by the buildup of some toxic
chemicals and an elemental imbalance that is injurious to plant
growth.
90
91. …cont’d
Causes of soil degradation
natural and human-induced causes.
Topographic and climatic factors such as steep slopes, frequent
floods and tornadoes, storms and high-velocity wind, high-
intensity rains and drought in dry regions
Deforestation and overexploitation of vegetation, overgrazing,
indiscriminate use of agrochemicals and lack of soil conservation
practices, and over extraction of ground
91
92. …cont’d
6.2.4. Soil Erosion Control Measures
We have two major soil erosion control mechanisms.
A.Biological Control measures
include vegetative strips, plantation, and reforestation.
prevent splash erosion, reduces the velocity of surface runoff,
increases surface roughness which reduces runoff and increases
infiltration,
92
93. …cont’d
B. Physical control measures
control the movement of water and wind over the soil surface.
physical erosion control measures commonly applied in Ethiopia
includes terracing, check dams, gabion, trenches, contour
ploughing, soil bunds etc
93
94. 6.3. Natural Vegetation of Ethiopia
6.3.1.Introduction
Natural vegetation refers to a plant cover that develops with little
or no human interference
It can also be seen as any original plant cover grown in an area.
Its distribution on the surface of the earth is uneven majorly
controlled by factors such as climate, soil types, drainage
temperature and precipitation affect the spatial distribution and
the original plant cover of a region
94
95. …cont’d
the natural vegetation of an area becomes a very good indicator of
the climatic conditions.
Natural vegetation are vital for human beings in many ways.
These are can provide shelter, food, source of fuel, pasture and
grazing, raw material for industries, source of timber and non-
timber products.
moderating effect on local climate, as home of wild life,
medicinal values, minimizing soil erosion etc
Ethiopia's natural vegetation are to a large extent determined by
elevation (and temperature) and rainfall.
95
96. …cont’d
Lowlands due to their low rainfall and high temperature have
harsh environment and are characterized by xeromorphic plants
(plants which are adapted to drought and high temperatures)
Ethiopia possesses an estimated number of 6000 species of higher
plants of which 10% are endemic
6.3.2. Major Natural Vegetation Types of Ethiopia
Taking altitude into consideration it is possible to broadly classify
the vegetation belts of Ethiopia into the following five groups
96
97. …cont’d
1.Afro-alpine and sub-afro alpine Region 2. Forest Region 3.
Woodland Savannah Region 4. Steppe Region 5. Semi-desert Region
1.Afro-alpine and Sub-afro alpine Region
Ethiopia has the largest extent of Afro-alpine and sub afro-alpine
habitats in Africa
Also known as high mountain vegetation is similar to the Alpine
vegetation in temperate regions
These ecosystems are found on mountains having an elevation
ranging between 3,200 and 4,620 meters above sea level.
97
98. …cont’d
The Afro-alpine habitat covers nearly 1.3% of the total landmass
of Ethiopia
Like any other landform in Ethiopian, the climate of Afro-alpine
ecosystems is controlled by latitude and altitude
The annul precipitation which ranges between 800 and 1,500 mm,
is mostly in the form of sleet or snow.
Temperature records of 0 oC and below are widely experienced in
these ecosystems.
Soils in this ecosystem are mostly shallow and eroded.
98
99. …cont’d
The Bale and Semein mountains are typical examples of afro-
alpine vegetations.
Compared to the Afro-alpine, the Sub-afro-alpine region is found
at a lower elevation, roughly between 3,300 and 4,000 meters.
Vegetation in the Afro-alpine region consists of tussock
grasslands, scrub, scattered mosses and lichens while the Sub-
afro alpine region is dominated by woodland, often degraded to
scrub stages and also wet grasslands.
99
100. …cont’d
Lobelia rhynchopetalum (giberra) and Erica arborea (Asta) are
some of the dominant species in the Afro-alpineand Sub-afro
alpine regions respectively
2. Forest Region
Forest is a complex ecosystem consisting predominantly of trees
that shield earth and support numerous life forms
In any geographical region, environmental factors such as climate,
soil types, topography and elevation determine the types of
forests.
10
0
101. …cont’d
In Ethiopia, forests are found at different elevations, 450 to 3,500m
in humid parts and 2,300 to 3,300 m in most arid parts.
Moreover, forests are characterized by variation in mean annual
rainfall that range between 200 and 2,200mm.
These wide variations in rainfall and altitude result in two broad
classification of forests: Highlands and Lowland forests
Highland forests include Hagenia Abyssinia (Kosso), Juniper procera
(tid), Arundinaria Alpina(kerkha),Podocarpusfalcatus (zigba),
Aningeria adolfi-friedericii (keraro) and Olea africana (Weyra)
forests; while Baphia are classified as lowland forests.
10
1
102. …cont’d
Moreover, there are also Gallery (Riverine) Forests.
These are forests that stretch along the banks of the lower courses
of rivers.
Riverine forests are classified as lowland forests and are found in
some places such as the banks of Awash, Wabishebelle, Ghenale
etc.
Dominant species include Ficus sur (sholla) and different kinds of
acacia trees.
10
2
104. …cont’d
3. Woodland Savannah Region
Like the forests, the woodland savannahs are also found in areas of
wide altitudinal ranges (250 to 2,300 m).
Although the mean annual rainfall ranges between 200 and 1,400
mm, the large part of this region is found at a lower elevation and in a
drier environment.
The plants in the woodland savannah are known for their
xeromorphic characteristics like shading of leaves during the dry
season.
10
4
105. …cont’d
Vegetation types with intermediate characteristics between
savannahs and woodlands are shrub lands and bush lands
Woodland savannah region can be broadly classified into three
divisions:
Juniper procera (tid) is dominant species for both the Junipers Forests
and Junipers Woodlands. The difference is in height: 3 - 45 meters
tall in the forests and 10 -15 meters in the woodlands.
Acacia woodlands are dominated by both trees and shrubs, which
belong to the same genus 'Acacia'. E.g. Acacia etbaica(grar),Acacia
mellifera (Konter
10
5
106. …cont’d
Mixed deciduous woodlands: As the name implies, most of the
trees in mixed deciduous woodlands shed their leaves during the
dry season.
10
6
107. …cont’d
4. Steppe and Semi Desert Regions
These are regions in the arid and semiarid parts of the country
where the temperature is very high and the rainfall very low
Both are found at low elevations, the steppe at elevations of 100
to 1,400 m above sea level and the semi-deserts at 130 meters below
sea level to 600 meters above sea level.
The steppe gets a mean annual rainfall of 100 to 550 mm as
compared to 50 to 300 mm for the semi desert areas
10
7
108. …cont’d
Growing period lasts up to 2 months for the steppe and a
maximum of one month for the semi-deserts.
Even though there is a variation in the degree of alkalinity and
salinity; soils in both regions are generally alkaline and saline.
In these regions xerophytic (i.e. drought-resisting plants) are the
dominant vegetations. Xerophytic plants such as short shrubs,
scattered tufts of grass species and a variety.
10
8
109. …cont’d
Where there are moist soils, rich vegetation of acacia and palm
trees may be observed. Trees are normally restricted to fringes
along watercourses; Natural vegetation map of Ethiopia
10
9
110. …cont’d
6.3.3. Natural vegetation Degradation
Over the past century, a rapid growth of the already dense
Ethiopian population has led to overexploitation of the land.
In areas with settled agriculture, new land has been cleared at
the expense of forests.
Ethiopia's forest resources have been disappearing at an alarming
rate.
A century ago, forests covered about 40 % of the total land area.
For the last few decades, forests have been cleared for different
reasons.
11
0
111. …cont’d
Major causes for the gradual disappearance of the natural vegetation in Ethiopia are:
Clearing of forests for cultivation
Timber exploitation practices
Charcoal burning and cutting for fuel
6.3.2. Natural Vegetation Conservation
There are three main approaches of biodiversity conservation:
1. Protection; sanctuaries, national parks, and community conservation areas.
11
1
112. …cont’d
2. Sustainable forest management
3. Restoration or rehabilitation
6.4. Wild Life/wild animals in Ethiopia
Ethiopia has about 860 avian species (16 endemic species and two
endemic genera), 279 species of mammals (31 endemic species and
six endemic genera), 201 species of
reptiles (14 endemic species), 23 species of amphibians (23 endemic
species), and 150 freshwater fish (6 endemic species)
11
2
113. …cont’d
A total of 279 mammalian species of which 31 are endemic are
known to occur in Ethiopia including those that require urgent
conservation action i.e. Walia Ibex (Capra walie), Gelada Baboon
(Theropithecus gelada), Mountain Nyala (Tragelaphus buxtoni),
Ethiopian Wolf (Canis simensis), Starck’s Hare (Lepus starcki).
Generally speaking, the main wild life concentrations in the
country occur in the southern and western parts.
11
3
114. …cont’d
The wild animals in Ethiopia can be classified into five major
groups:
1.Common wild animals (those animals that are found in many parts
of the country (e.g. hyenas, jackals)
2.Game (lowland) animal, (which include many herbivores like
giraffes, wild asses, zebras etc. and carnivores like lions, leopards,
and cheetahs)
3.Tree animals or arboreals (which include monkeys, baboons)
11
4
115. …cont’d
4. A variety of birds in the Rift Valley lakes
5. Rare animals-These are wild animals found only in Ethiopia.
These days Ethiopia’s endemic animals exist in only very small
numbers. They inhabit highland and other areas. The following are
some of them.
Walia Ibex (wild goat), found in the Semein highlands.
Mountain Nyala (Dega Agazon), found in the Bale mountains.
11
5
116. …cont’d
Gelada’ or ‘Chelad’ baboon, found in the Semein highlands.
Menilik’s Bushbuk (‘Dikula’) in the Shoan and Bale highlands
Swayne’s Hartebeest (‘Korkay’), found in the Nechsar park and
the Sankalle sanctuary.
Semein Fox (‘Key Kebero’), found in the Bale and Semein
Highlands.
Wild Ass (Yedur Ahiya), found in the Afar and Southeast
Lowlands.
11
6
117. …cont’d
6.4.2. Wildlife Conservation
Wild animals can be used for:
scientific and educational researches
physical and mental recreation (aesthetic value)
promotion of tourism (economic value)
its potential for domestication
maintaining ecological balance
To prevent the destruction of wildlife a total area of nearly 100,000
square kilometers of national parks, sanctuaries, community
conservation areas, botanical gardens, wildlife
11
7
118. …cont’d
21 major national parks- National parks are conservation areas
for wild animals in which legal hunting is allowed, with some
restrictions.
2 major wildlife sanctuaries- Sanctuaries are wild-animal
conservation areas where hunting is strictly prohibited. Example:
Babille, Sankale,
3 wildlife reserves, 6 community conservation areas, 2 wildlife
rescue centres,
22 controlled hunting areas,
17 Game reserves- are wild-animal conservation areas where
tourists are allowed to practice licensed hunting.
11
8
