Do tree shelterbelts have the relative advantage to convince farmers to grow
them: an empirical example from the Gezira Agricultural Scheme, Sudan.
Siddig El Tayeb Muneer
Department of Agricultural Extension and Rural Sociology
Faculty of Food and Agricultural Sciences
King Saud University
Do tree shelterbelts have the relative advantage to convince farmers to grow
them: an empirical example from the Gezira Agricultural Scheme, Sudan.
Abstract:
One of the major environmental problems facing the arid, semi-arid and dry subhumid areas of the world and causing substantial reduction in agricultural
production and agricultural income of many farmers is desertification. In Sudan
desertification is considered one of the main causes of low crop productivity in
many areas, among which is North West part of the Gezira Agricultural Scheme. In
1991 the scheme administration started establishing a tree shelter–belt to protect
the entire scheme from desertification, starting with the most affected areas (like
Abu Gota and Bagigah blocks) in the North West part of the scheme. This study is
intended to examine the effect of this tree shelter-belt in mitigating the negative
impacts of desertification.
Abu Gota block of the Gezira Agricultural Scheme which is one of the most
affected areas by desertification and where the tree shelter-belt is established was
chosen as the study area. The data was collected through personal interviews with a
stratified random sample of 300 farmers. Chi-square test is used to analyze the
data.
The study results indicates that farmers whose farms are located close to the tree
shelter-belt were less affected by desertification and consequently they obtained
high agricultural production and income compared to those whose farms are
located far from the tree shelter-belt and they tend not to resort to poverty coping
strategies such as hiring their family labor to others and pulling their children out
of school.
Introduction
Agriculture plays a vital role in the economy of many countries. In such countries a
large portion of the population earn their income from utilizing agricultural natural
resources such as agricultural land, irrigation water, forests, grazing lands etc…
and in many countries these resources are increasingly overexploited and problems
like rural poverty, food insecurity and rural-urban migration are encountered. The
poor in the rural areas of the developing countries are often forced by
circumstances and factors beyond their control to destroy the few resources
available to them (de Boom, 1990; FAO, 1992). By doing so, they are ultimately
trapped in a vicious circle of lack of food and fuel on one hand, and deterioration
of the environments producing these necessities on the other hand. Therefore,
many researchers associate poverty and environmental degradation and argue that
the relationship between them is direct and symmetrical; i.e. poverty induces
environmental degradation and environmental degradation deepens poverty
(Grainger, 1982; Nicholson, 1986; de boom, 1990; FAO, 1994). Furthermore, and
because of the fact that the poor constitute the majority of the adopters’ category
labeled as laggards who are not expected to adopt any environmental conservation
or rehabilitation innovation (Rogers, 1993), reinforces the vicious spiral of poverty
and environmental degradation and makes it difficult to be halted. In the case of
environmental problems related to desertification and deforestation, the problem is
even aggravated more by the negative attitude usually some farmers have towards
the presence of trees in their farms. Farmers usually believe that trees make less
land available for planting crops and harbor insects and birds that damage their
crops (Clarke and Thaman, 2006).
1
One of the major environmental problems facing the arid, semi-arid and dry subhumid areas of the world and closely related to poverty is desertification.
Desertification is caused by various factors including climatic changes and human
activities and, it is accompanied by a reduction in the natural potential of the land
and a decrease in surface and ground water resources and has negative
repercussions on the living conditions and economic development in the affected
areas. Worldwide, desertification affects about two thirds of the countries of the
world and one third of the earth’s land surface (about 4500 million hectares) which
is inhabitant by approximately one billion people (FAO, 2006). One of the main
important causes of desertification is deforestation. Deforestation means the loss of
trees with its many functions. It is attributed to factors such as cleaning of land for
horizontal agricultural expansion and excessive trees cutting for fuel-wood
consumption. The most desertification affected regions are the Sudano-Sahelian
regions followed by Africa south of the Sudano-Sahelian region and South Asia.
Sudan is one of the Sudano-Sahelian regions that are severely affected by
desertification. Bayoumi (1984), reported that in Sudan human activities were
responsible for the loss of 20 million metric tons of wood annually. Furthermore, it
has been observed that severe cutting of national forests east of the White Nile
allowed the encroaching sand to reach the Gezira scheme, clog the canals and
cover the villages in the affected areas (FAO, 1986). In the past these forests acted
as a barrier to the moving sands.
Problem Statement
The Gezira Scheme is the largest agricultural scheme in Sudan with an area of 2.1
million feddans1. It lies south of Khartoum between the Blue and White Niles.
It is irrigated by gravity irrigation2 from Sennar Dam. It provides livelihood for
more than 100,000 farmers and families. Before mid 1970s the scheme was
1
Feddan = 0.42 hectar
Gravity irrigation is directing the water to flow down taking advantage of the natural slope of the
land (gradient) without pumping and/or lifting.
2
2
adopting a farming system where only cotton was receiving all the official
attention and sorghum and beans were grown as farmers’ crops and necessary
components of the rotation. After then, a diversified farming system is adopted and
the farmers are encouraged to produce wheat, sorghum, groundnut and vegetables
in addition to cotton. The scheme contributes significantly to the country economy.
It produces about 80%, 30%, 60%, 60% and 20 % of the country total production
of long stable cotton, medium stable cotton, groundnut, wheat and sorghum
respectively; in addition to considerable amounts of vegetables, fruits and milk
(Sudan Gezira Board, 1992).
One of the main problems causing low crop productivity in the scheme,
particularly in the northwest boundaries, is desertification. Consequently, in 1967
the scheme administration (Sudan Gezira Board) had established a protective tree
shelter - belt, the Tahamied shelter - belt, which is believed to play an effective role
in mitigating desertification negative impacts. During recent years this belt is not
managed properly (i.e. not properly irrigated and not protected against cutting and
grazing). This has led to appearance of large gaps through which moving sands
entered the fields, clogged irrigation canals and made irrigated agriculture difficult
or impossible in some cases (FAO, 1986; Forestry Administration, 1987). A study
conducted by the University of Gezira (1987) to examine the negative impacts of
desertification in the Gezira Scheme indicated that sand encroachment has resulted
in irrigation problems such as burial of canals and coverage of fields with sand
which led to reduction in the cropped area. Consequently, farmers in severely
affected areas are unable to grow some crops that are grown during the dry season
and have high water requirements and even the grown crops neither get the
required number of irrigations, nor the optimum quantity of water per irrigation.
Furthermore, sand encroachment on the fields made gravity irrigation difficult and
the water requirements of the different crops had increased due to the increased
evapotranspiration. Moreover, soil fertility is expected to change depending on the
type of the added soil. Plants’ height and leaves were also affected by blowing
winds. All this has resulted in low crop productivity and agricultural income which
in turn caused migration, particularly of young people, from the affected areas
(Echholm, 1984; United Nations Environment Program, 1986).
Although there are no accurate statistics about the size of the area affected by
desertification in the Gezira Agricultural Scheme, there is no doubt that it is
increasing annually (Mohamed, 1994). Accordingly, in 1991 the scheme
administration started establishing a new tree shelter–belt to protect the entire
scheme from desertification, starting with the most affected areas (like Abu Gota
and Bagigah blocks) in the North West part of the scheme (Forestry
Administration, 1995).
Thus, this study aims at examining the relative advantage of this tree shelter-belt in
terms of its role in mitigating desertification effect in Abu Gota block and how it
could be used to encourage farmers’ participation in the forestation efforts.
Objectives of the study:
The study aims at:
1. Examining the effect of the tree shelter-belt on the total cropped area by each
farmer.
2. Assessing the effect of the tree shelter-belt on the farmer’s total agricultural
income.
3. Assessing the effect of the tree shelter-belt on agricultural productivity.
4. Exploring the role of the tree shelter-belt in mitigating desertification effects.
3
Methods:
One of the most affected areas by desertification in the North West part of the
Gezeira Agricultural Scheme and where the new tree shelter-belt is established
(Abu Gota block) was chosen as the study area. The total area of this block is
20161 feddans and it is cultivated by 1305 farmers who represent the study
population. About one third of the farmers in the study area are near the tree
shelter-belt which is believed to mitigate desertification effects particularly with
regard to blocking of irrigation canals and consequently availability of irrigation
water. Accordingly, the farmers in the study area were divided into two categories
based on how close their farms are to the tree shelter-belt and the extent to which
their farms were affected by desertification. About one third of the farmers were
identified as near the tree shelter-belt and less affected by desertification and two
thirds as away from the tree shelter-belt and more affected by desertification.
A random sub-sample of 100 farmers was selected from the farmers’ group
identified as near the tree shelter-belt whose farms are located about 1.5 Kilometers
or less from the shelter-belt. Another random sub-sample of 200 farmers was
selected from the farmers’ group identified as away from the tree shelter-belt
whose farms are located more than 1.5 Kilometers away fro the shelter-belt. Thus,
a stratified weighted random sample of 300 farmers was selected. Chi-square test is
used to examine the differences between the two groups of farmers in terms of the
extent to which they were affected by desertification and the strategies they used to
cope with those effects.
Measurement of some of the study variables:
1. Gross farm income: Was measured by the total monetary value of all the crops
grown by each farmer.
2. Farm productivity: was measured by gross farm income per feddan and was
obtained by dividing the total gross farm income by the total area of all crops
grown.
3. Cropped area: Was measured by the total area of all crops grown by each
farmer in feddans.
4. Number of days the family members worked as hired laborers: Was measured
by the total number of days the family members (whom their primary
occupation is agriculture) worked as hired laborers for others in their village or
outside their village.
5. Average school drop-out rate: Was measured by the number of the household
members who are in the school age (6 – 22 years) and not attending school
divided by the total number of the household members who are in the school
age (6 -22 years).
Literature review
To understand the relationship between poverty and environmental degradation
(usually referred to as the vicious circle), it is useful to distinguish between two
types of poverty: conjunctional poverty and structural poverty (Tigani, 1990).
Conjunctional poverty occurs when people loose their wealth and assets during
times of natural disasters and environmental problems such as droughts and floods
or man made disasters such as wars. As a result of conjunctional poverty that is
induced by natural environmental degradation, people will either over-exploit and
misuse the remaining natural resources or migrate to other areas (usually big cities)
where they cause pressure on the already limited services and deteriorating
environment. Thus, by impoverishing the natural potential of ecosystems,
environmental problems such as desertification, reduce agricultural yield and make
4
it less predictable and render rural population in the affected areas vulnerable to
food shortages, the vagaries of weather and natural disasters. In order to get their
most urgent needs people will develop survival strategies which in turn aggravate
environmental problems such as desertification and impede development. The
other type of poverty is structural poverty which usually results from structural
adjustment and economic reform policies and it affects certain segments of the
population because of their personal characteristics (e. g. small farmers, women,
female-headed households, wage workers etc…). Again, and in order to get their
basic needs and necessities people who are affected by structural poverty will be
engaged in activities that will lead to environmental degradation (de Boom, 1990).
Thus, while conjunctional poverty is the consequence of environmental
degradation, structural poverty is the cause of environmental degradation.
One of the main environmental problems facing the world and closely related to
poverty, particularly in rural areas, is desertification. Desertification as defined in
Chapter 12 of Agenda 21 and in the International Convention on Desertification is
the degradation of the land in arid, semi-arid, and dry sub-humid areas resulting
from various factors, including climatic variations and human activities
(Koohafkan, 2006). It manifests itself initially in destruction of soil fertility,
declining crop yield, a change in the quality and quantity and diversity of
vegetation where perennial trees and grasses decrease, palatable and nutritious
plants are replaced by less valuable species, or even toxic shrubs (Echholm,1976).
Consequently, it is accompanied by a reduction in the natural potential of the land
and a decrease in surface and ground water. Thus, it leads to a reduction of plant
biomass and land carrying capacity to support crops and livestock and has negative
repercussions on the living conditions and economic development in the affected
areas (United Nations, 1977).
Different investigators had reported different causes of desertification in different
parts of the world (Ibrahim, 1978; Mabbutt, 1984; Noordwilk, 1984; Grainger,
1990). Nevertheless, the most important and common causes of desertification
include: land clearance and over-cultivation, which refers to the expansion in
cropping (both rain-fed and irrigated) and shortening of fallow periods. It occurs
when farmers try to use land more intensively regardless of its natural fertility and
without adding fertilizers or allowing it to generate its fertility naturally. Therefore,
over-cultivation reduces the soil fertility, damages its structure and exposes it to
erosion. The second cause is over-grazing, which occurs when the number of
livestock is increased beyond the carrying capacity of the range-land, leading to the
destruction of vegetation and the compaction and erosion of the soil. In Sudan,
over-grazing is caused by the enormous increase in livestock, deterioration of
range-land, and settlement of nomads so as to be provided with improved services
and development of water points (de Boom, 1990). A third cause of desertification
is deforestation. Natural and cultivated vegetation plays an essential role in
protecting the soil, particularly trees and bushes which due to their long life and
their capacity to develop powerful root systems, guarantee effective protection
against soil degradation (FAO, 2006). Therefore, deforestation, which means
disappearance of trees with its many functions, increases the vulnerability of the
land to desertification considerably. Deforestation is attributed to factors such as
cleaning of land for horizontal agricultural and urban expansion and excessive trees
cutting for fuel-wood consumption. Clarke and Thaman (2006) reported that
deforestation has led to severe erosion in the pacific islands (Wallis and Futuna, the
Cook Islands, French Polynesia) where most of the indigenous forest has been
5
removed , leaving degraded lands and grasslands no longer suitable for agriculture
and they argued that Pacific Islanders, like people everywhere, prospered by
disturbing the natural order. Bayoumi (1984) reported that in Sudan human
activities were responsible for the loss of 20 million metric tons of wood annually.
Furthermore, it has been observed that severe cutting of national forests east of the
White Nile allowed the encroaching sand to reach the Gezira scheme and clogged
the canals and covered the villages in the affected areas (FAO, 1986). In the past,
these forests acted as a barrier to the moving sands. A fourth factor that contributed
to desertification is drought. Although, there is no conclusive consensus about the
relationship between drought and desertification, there is no doubt that drought
makes the impacts of desertification, which are reflected in crop failure, livestock
mortality etc.., more felt by those living in the affected areas (Grainger, 1990;
Nicholson, 1986).
Bellefontaine et al. (2000) indicated that over the past few decades several of
desertification causes have been at work; fallow periods are increasingly being
curtailed, soil is becoming ever less fertile, land clearance for agricultural and other
purposes is being stepped up, overgrazing is increasing and fuel-wood needs are
constantly rising. Thus desertification is expected to be a real threat to livelihood of
many people worldwide. Consequently, and because of it’s devastating effects it
has been widely accepted that combating desertification must form an integral part
of the socioeconomic development programs for the affected areas and it requires
full participation of the local people (FAO, 2006). Therefore, participatory forest
management as a concept and a goal has become widely accepted for the
management of forest (Gilmour, 1995; FAO, 1998). Participatory forest
management is concerned with managing the forest as a complex valuable natural
resource system that has several crucial functions and not only as a source of wood.
Participation of the local people is considered one of the principles of participatory
sustainable forest management (FAO, 1998).
For farmers to adopt any new practice, such as participation in forest management
and forestation programs, they have to perceive that it has a relative advantage
which is beneficial to them. Innovation’s relative advantage is usually expressed in
economic profitability, in status giving, or in other ways. Diffusion scholars have
found relative advantage to be one of the best predictors of an innovation’s rate of
adoption and for some innovations and for some adopters, economic aspects of
relative advantage (profitability) may be the most important single predictor of rate
of adoption (Rogers, 1993). In some studies it was possible to explain about 30
percent of the variation in rate of adoption on the basis of economic relative
advantage (Griliches, 1957; Dixon, 1980). In a study of adoption of biomass
improved cook-stoves in Sudan, it was found that the perceived innovation’s
relative advantage in terms of reduction of charcoal cost was the most important
factor affecting households’ innovativeness (Muneer and Mohamed, 2003).
Induced economic relative advantage in terms of price subsidies and incentives was
found to be one of the important factors that encouraged farmers in Al-Zulfy area
of Saudi Arabia to adopt modern irrigation systems (Muneer and Al-Sakran, 2003).
Also in Saudi Arabia, farmers who planted Date Palm seedlings produced through
tissue culture technology indicated that the most important factor that convinced
them to adopt this innovation was it’s low cost (Al–Sakran and Muneer, 2006).
Therefore, for farmers to participate effectively in forestation programs, they have
to be persuaded that these trees and forests are beneficial to them in one way or
another (i.e. they have a relative advantage).
6
Results and discussion:
Desertification has negatively affected agriculture and the living conditions of
people in the northern parts of Gezira Agricultural Scheme in different ways. By
blocking irrigation canals it has made less irrigation water available and many
farmers can’t make use of their farms because of shortage of irrigation water.
Moreover, the grown crops can neither get the recommended number of irrigation,
nor the required quantity of water per irrigation. Furthermore, desertification
covers the agricultural land with sand which lowers land productivity and increases
the cost of land preparation and consequently, agriculture in the affected areas has
become less profitable. Consequently, farmers have abandoned agriculture as their
main occupation and started to work as agricultural laborers for other farmers in
other villages which are not affected by desertification and some of them even
migrate to cities. The tree shelter-belt is expected to mitigate these negative
impacts of desertification.
Table (1) shows that the majority of the respondents (42.6%) were young farmers,
while about one fifth of them were older than sixty years. This is conducive to the
diffusion and adoption of tree shelter-belt as young farmers are usually more
innovative than old farmers (Rogers, 1993). On the contrary, about two thirds of
the respondents were illiterate and only 14.2% of them completed the secondary
school. This puts more burden on the agricultural extension agents as illiterate
farmers usually require more effort to be convinced to adopt new technologies and
practices.
Table 1. Some demographic characteristics of the respondents
Demographic characteristics
Number
1. Age:
≤ 40 years
128
41 – 60
109
> 60 years
063
2. Education:
Illiterate
198
Primary or Intermediate School
059
Secondary School
043
Percentage
42.6
36.4
21.0
66.0
19.8
14.2
Table (2) reflects the effect of tree shelter-belt on the total area cultivated by the
farmers. It is clear that the majority (70%) of the farmers whose farms are located
far from the tree shelter-belt did not cultivate large or even medium areas of their
farms. Respondents attributed this mainly to lack of enough irrigation water due to
irrigation canals being blocked by sand. A second reason indicated by the
respondents for cultivating small area is the farmers’ perception that agriculture is
no longer a profitable occupation because of the high cost of production and the
decrease of their farm productivity caused by desertification. On the other hand,
about two thirds (63%) of the farmers whose farms are close to the tree shelter-belt
cultivated medium size areas and about one third (31%) of them cultivated large
areas and most of them indicated that desertification effect on their farms with
regard to availability of irrigation water, is very minor. Chi-square test has revealed
that the difference between the farmers whose farms were identified as close to the
tree shelter-belt and those whose farms were identified as far from it regarding the
size of the total cultivated area is statistically significant at (< 0.001) level of
significance. This suggests a very strong association between the size of the total
7
cultivated area and the location of the farm with regard to the tree shelter-belt. This
is a very clear relative advantage of the tree shelter-belt that should be used and
emphasized by the agricultural extension service in the Gezira Agricultural Scheme
to increase farmers’ awareness, even in areas not affected by desertification. The
role of trees and forests in controlling and mitigating desertification effects, if
popularized, will motivate and persuade the farmers to actively participate in the
forestation programs implemented by the Scheme Administration to establish a tree
shelter-belt around the whole Scheme.
Table 2. Tree shelter-belt effect on total cultivated area of all crops
Total cultivated area
Location of the farm from the
(All crops)
tree shelter belt
Far
close
Small cultivated area
140
6
(Less than 4 feddans)
Medium cultivated area
53
63
(4 – less than 8 feddans)
Large cultivated area
7
31
(8 feddans or more)
Total
200
100
Chi-square = 118.88 (P < 0.001)
Total
146
116
38
300
In addition to its effect on the total area cultivated by each farmer, the tree shelterbelt is expected to have positive effect on land productivity as the soil fertility will
be less decreased by desertification and the crops will get the required number of
irrigations and the proper amount of water per irrigation. The results presented in
table (3) support this thesis, where 30 percent of the farmers whose farms are
located away from the tree shelter-belt got low productivity while no one of those
whose farms are close to the tree shelter-belt obtained low productivity. On the
other hand, the majority (70%) of the farmers whose farms are close to the tree
shelter-belt obtained high productivity compared to only one fourth of the farmers
whose farms are located far from the tree shelter-belt who obtained high
productivity. The negative association between the farm productivity and its
distance from the tree shelter-belt is statistically significant at (< 0.01) level of
significance.
Table 3. The effect of tree shelter-belt on farmers’ agricultural productivity
Location of the farm from the
Productivity level (LS)3
Total
tree shelter-belt
Far
close
Low productivity
60
0
60
(Less than 1.5 millions)
Medium Productivity
90
30
120
(1.5 – less than 3 millions)
High Productivity
50
70
120
(3 millions or more)
Total
200
100
300
Chi – square = 67.5 (P < 0.01).
3
LS = Sudanese Pound (1 US$ = LS 2001.0)
8
Again, this is a very convincing relative advantage of the tree shelter-belt that
should be stressed and emphasized by the extension workers to increase farmers’
level of awareness about the importance and benefits of trees and forests in
improving their agricultural income which is a very crucial step towards their
participation in forestation programs.
In order to be able to get their basic needs people in the areas affected by
desertification usually develop and use survival strategies that are most likely
represent impediments to development in these areas. Thus, it has been argued that
in such areas desertification control must form an integral component of the
socioeconomic development programs (FAO, 2006). Among these survival
strategies is the work of some of the family members as hired laborers for others in
nearby villages that are not affected by desertification and seasonal migration of
some of them to cities which might turn into permanent migration. Table (4)
illustrates the consequences of desertification in terms of the extent to which some
of the farming household’s members abandoned agriculture and worked as hired
laborers for others and the role of the tree shelter-belt in mitigating that through
revitalization of agriculture. While more than three quarters (78%) of the farmers
whose farms are near the tree shelter-belt did not have any of their household
members, for whom agriculture is the main occupation, worked as hired laborers
for any time, only 47% of the households whose farms are identified as away from
the tree shelter-belt did not have any of their members, for whom agriculture is the
main occupation did not worked as hired laborers. On the other hand, while only
about one tenth (11%) of the households whose farms are near the tree shelter-belt
had their members worked large number (more than 100) of days as paid laborers,
more than one fifth (23%) of the households whose farms are away from the tree
shelter-belt their households’ members did that. This negative correlation between
the average number of days that the household members worked as hired laborers
for others and the distance of their farm from the tree shelter-belt is statistically
significant at (< 0.01) level of significance.
Table 4. Number of days households’ members worked as hired laborers by the
location of the household farm with regard to the tree shelter-belt
Number of days household
Location of the farm from
members worked as hired laborers
the tree shelter-belt
(Days)
Total
Far
close
Did not worked (0)
Less than 100 days
More than 100 days
Total
Chi-Square = 26.8 (P < 0.01).
94
60
45
199
78
11
11
100
172
71
56
299
The ultimate consequence of desertification is the widespread of rural
conjunctional poverty (Tigani, 1990; FAO, 2006) due to reduction in agricultural
production and agricultural income. One of the very detrimental effects of poverty
is high school drop-out rate where the children leave the school because their
families will not be able to pay the school costs and prefer to let them work as
hired laborers to substitute the drop in their agricultural income. Table (5) indicates
that only 23.5% of the families whose farms are away from the tree shelter-belt did
9
not have any of their children, who are in the educational age (6-23 years), dropped
out of the school compared to 69% of the families whose farms are near the tree
shelter-belt. On the other hand, while 30.5% of the households whose farms are
away from the tree shelter-belt had three or more of their children dropped out of
the school, only 7% of the households whose farms are close to the tree shelter-belt
had that number of school drop-out. Chi-square test revealed that the positive
association between the distance of the household farm from the tree shelter-belt
and the number of the household children who dropped out of the school is
statistically significant at (P < 0.01) level of the significance. This relationship
exists because of the presence of intervening variables (Bailey, 1994) that are
related to the farm distance from the tree shelter-belt and in turn cause dropping
out of school. These intervening variables are desertification and the family
agricultural income:
Long distance of the farm from the tree shelter-belt
↓
The farm being more affected by desertification
↓
Low agricultural production and low agricultural income (poverty)
↓
Large number of school drop-out (as one of poverty coping strategies)
Table 5. Number of the household member school drop-out by their farm distance
from the tree shelter-belt
Number of school
Location of the farm from the tree
drop-out
Total
shelter-belt
Far
close
No school drop-out
47
69
116
1 -2
92
24
116
More than 2
61
7
68
Total
200
100
300
Chi-Square = 60.281 (P < 0.001)
Conclusion:
The study results are very consistent with the literature on agroforestry and role of
forests and wind-breaks in desertification control. Farmers whose farms are
located close to the tree shelter-belt were less affected by desertification and
consequently they obtained higher agricultural production and agricultural income
compared to those whose farms are located far from the tree shelter-belt. Thus, the
households whose farms are close to the tree shelter-belt were not compel to resort
to poverty coping strategies such as hiring their family labor to others and pulling
their children out of school. This is a very tangible relative advantage of the tree
shelter-belt that should be stressed and emphasized by the agricultural extension
service to enhance farmers’ participation in forestation programs.
10
References
Al-Sakran, Muhamed S. and Muneer, Siddig E. (2006). Adoption of Date Palm
Tissue Culture Technology Among Date Palm Producers in the Central
Region of Saudi Arabia. Research Bulletin No. 145. King Saud
University: College of Food and Agricultural Sciences- The Research
Center.
Bailey, Kenneth D. (1994). Methods of Social Research (4th Edition). New York:
The Free Press.
Bayoumi, A. (1984). Renewable natural resources management and desertification
in Sudan. Sudan Journal of desertification (2): 1 – 4.
Bellefontaine, R.; Gaston, A. and Petrucci, Y. (2000). Management of Natural
forests of dry Tropical Zones. FAO Consultation Guide 3. Rome: FAO.
Clarke, W. C. and Thaman, R. R. (2006). Agroforestry in the Pacific Islands:
Systems for Sustainability. Suva (Fiji): The University of the South
Pacific.
De Boom, C. J. (1990). Environmental problems in Sudan (Part I). The
Netherlands: Institute of Social Studies (ISS).
Dixon, Robert (1980). Hybrid Corn Revisited. Econometrica: 48: 1451 – 1461.
Echholm, E. (1984). Desertification control. United Nations Environment
Program.
Echholm, E. (1976). Losing ground. New York: Norton.
FAO (2006). Desertification and drought: extent and consequences. Rome: FAO,
Agriculture Department.
FAO (1998). Guidelines for the management of tropical forests: The production of
wood. FAO forestry Paper No. 135. Rome: FAO.
FAO (1994). Policies for sustainable development. FAO economic and
development paper No. 121. Rome: FAO.
FAO (1992). Community Forest: Ten Years in Review. Rome: FAO.
FAO (1986). Irrigated forest plantations as an integral part of agriculture: a
proposal for 5 years development plan for the central region of Sudan.
Rome: FAO, Fuel Wood Development Program.
Forestry Administration (1995). Annual report (in Arabic). Gezira Scheme
(Sudan): Forestry Administration.
Forestry Administration (1987). Annual report (in Arabic). Gezira Scheme
(Sudan): Forestry Administration.
Gilmour, D.A. (1995). Conservation and Development: seeking the linkage. In H.
Wood, McDaniel & K.Warner (eds.) Community development and
conservation of forest biodiversity through community forestry.
Proceeding of International Seminar held in Bangkok (Thailand),
October 26-28, 1994.
Grainger, A. (1982). Desertification. London: Earthscan.
Grainger, A. (1990). The Threatening Desert. United Kingdom: International
Institute for Environment and Development.
Griliches, Zvi (1957). Hybrid Corn: An Exploration in the economics of
Technological Change. Econometrica , 25: 501 – 522.
11
Ibrahim, N. F. (1978). The problem of desertification in Sudan with special
reference to Northern Darfur province. Khartoum: Develoment Studies
and Social Research Center. Monograph Series No. 8.
Koohafkan, A. P. (2006). Desertification, drought and their consequences.
Sustainable Development (SD) dimensions. Rome: FAO: Environment
and Natural Resources Service.
Mabbutt, J.A. (1984). A new global assessment of the status and trends of
desertification. Environmental Conservation Volume II (2): 103 – 113.
Mohamed, Ahmed El Amin A. (1994). The socioeconomic impacts of
desertification in the North-West boundaries of the Gezira Scheme.
M.Sc. Thesis. Department of Rural Economy, Faculty of Agriculture,
University of Khartoum.
Muneer, Siddig E. and Al-Sakran, Muhamed S. (20030. Adoption of Natural
Resources Conservation Practices in Al-Zulfy, In Saudi Arabia.
Research Bulletin No. 5/2003. Scientific Society of Agricultural
Extension (Egypt).
Munner, Siddig E. and Mohamed, El Waseilah M. (2003). Adoption of biomass
improved cookstoves in a patriarchal society: an example from Sudan.
The Science of the Total Environment 307: 259 – 266.
Nicholson, S. E. (1986). Climate, drought and famine in Africa. In Hansen and
McMillan (eds.) (1986). Food in Saharan Africa: 107 -128. Boulder
(Col.): Reinner.
Noordwijk, M. (1984). Ecology Textbook for the Sudan. Khartoum: Khartoum
University Press.
Rogers. Everett M. (1993). Diffusion of Innovations (4th Edition). New York: The
Free Press.
Sudan Gezira Board (1992). Gezira Board narrative report (in Arabic). Khartoum:
Gezira Board.
United Nations (1977). United Nations conference on desertification control: an
overview. Nairobi: The United Nations.
United Nations Environment Program (1986). The Encroaching Desert. The
consequences of human failure. A report for the Independent
Commission on the International Humanitarian Issues. London: Zed
Books LTD.
University of Gezira (1987). The Impacts of Sand Encroachment in North and
North West Parts Of Gezira Scheme (in Arabic). Sudan: University Of
Gezira.
Tigani, Mustafa (1993). Poverty: The problem and it's dimensions. A paper
presented to the workshop: Establishment of a bank for the poor,
organized by the Ministry of Social Planning in January 1990. Sudan:
Ministry of Social Planning.
12