Ethiopian Vegetation Agricultural
Land cover/use Study projects provide policy makers, industry and community interest groups, and landholders with accurate information on woody vegetation cover, information on changes in the cover, mapping and providing statistical information.
In earlier times the northern Ethiopian highlands were characterized by humid climate and denser vegetation (Bard et al., 2000). Significant human impact on the land resource resulted in 65 per cent of the total land mass to be a dry land. Land clearing for agricultural activity has become an increasingly main topic in the natural resource debate that contrasts the economic aspects of land development to the people dependent on it and with the ecological need to conserve.
According to Fainstain (1996), planning is a future-oriented public decision making directed towards attaining specific goals. In a broader sense, it is the sum total of all processes involved in the generation, analysis and interpretation of spatial data for decision making on the future use of the land in a better way than before. It includes the activities of spatial data collection on the existing land uses and land resources (land evaluation), analysis and interpretation of this data, generation of alternatives for land use and choosing the best option among them, assessing the impact of the new land uses chosen and recommendations for decisions on what is better for the future of the land (land use types and land management) to the decision makers.
One of the necessities for land use planning is to have land resources information obtained from land resource surveys or resource inventories which the land use plans will be based on.
The evolution of land evaluation, as indicated by Davidson (1992), tells us that it was taking place in a limited degree in the 1960s and1970s while the results were left idle on shelves than being used up for land use planning activity.
However, the years 1980s were times when land evaluation has started to show dramatic changes with emphasis on different types of land resource surveys. After a decade, in the 1990s, the science had further been acceleration and results were applied to land use planning and land management purposes. This led to an important achievement which was the introduction of the “customer-oriented” approach through which land resource survey institutions began to make land resource information available to their customers on market basis. The income from such approach enabled the institutions to be able to integrate land resource survey and land evaluation results with land use planning and management.
Following this, there developed land capability classifications to protect agricultural land from being lost to unplanned urban expansion or protect forest land from ever increasing agricultural expansion witnessed in developing countries like Ethiopia.
A third stage in the evolution of land use planning science was the development of impact assessment on the environment and prediction of future effects of different land uses on the physical and human environment before the decision on land uses were made. (Bogale, 2006)
Mean while in the mid-1980s another radical change had emerged in the science of land use planning by the technological improvements, the introduction and application of GIS that highly improved the imputing and processing of geographically referenced land resource data with more possibility of updating and correcting mapped data, integration of different data sets and modeling, producing precise out puts than ever before.
In the present days land use studies can be achieved under two basic methodologies- land evaluation and land capability/suitability classification, and GIS-based land use planning. As the ultimate objective of this paper is to develop land suitability classification input through economically viable state of the art technologies, only the first part of the above mentioned methodologies will be briefly presented.
Land Evaluation and Suitability Classification
Land resources are complex in their nature, i. e., quality, quantity, distribution, etc. One has to know the nature of the land resources before deciding any land use on the land. The stage in land use planning where we study the land resources in terms of their quality, size, and distribution through forming different mapping units (plots of land with relatively similar physical setting) is land evaluation. Land use planners, then, plan the new future land use plan for the area based on the information obtained from the land evaluation studies. There are different methodologies applied in land resource and land information studies, out of which the following are major ones (Davidson, 1992):
1. Land Resource Inventory- is the general study of the land resources as an inventory to get information on “what is where” including its quality, size and required management to use each land resource on a sustainable basis. The study goes through dividing the land in to plots of land, called mapping units and describing the nature of land resources together with management needed for long range use of the land. Based on this land information, therefore, suitable land use can be planned for each of the mapping units.
2. Agro-Climatic Surveys- are practiced by matching the distribution of climatic characteristics with plant requirements and then forming land units based on agro-ecological zoning. Following this any land use can be planned fitting to the plant climatic requirements and the management type required for each mapping unit.
3. Landscape approach- involves the characterization of land resources on the basis of the landscape of the area and describing the resources and management requirements for each mapping units which are delineated on landscape basis. The landscape approach is also an integrated survey that comprises information on all land resources for each of the mapping units (soil, geology, climate, topography, flora and fauna) which are all land resources for each of the mapping units that are divided in to land units based on the existing landscape of the area(s) under investigation.
4. Parametric-Ecological approach- Here separate information is gathered for each of the land resources on each of the mapping units formed on the basis of landscape. Then separate layers of information are prepared for each of the mapping units, as for soil, climate, geology, flora, fauna, etc, which will be integrated to form complete information of land resources for each of the mapping units. This is taken as better alternative with the application of GIS for the purpose.
Generally which ever land evaluation methodology of gaining land resource information is applied the final out put, land information, is given by mapping units, which then will be used as an input for land capability classification.
The land evaluation process gives us resource information and management requirements of each of the mapping units. The next task of the land use planner is to classify these lands into different land use types for which they should belong to on a sustainable basis based on the type of resources of the land, management type needed and individual nature of the land uses identified as options. This gives us the division of the land in to different land uses (classes) called land capability classes, while the process is land capability or suitability classification.
Land capability classification or suitability classification is becoming now a days widely accepted methodology by land use planners due to many factors, mainly the following. (Bogale, 2006)
- The growing need of land planners and land users to express risks before application of any land use and to develop land uses on a sustainable basis;
- The increasing awareness that land capability maps are comprehensive that give totalized information for soils, climate, geology, relief, erosion, etc. than the single information based soil maps;
- The increasing demand for planning control over land uses which enabled land users to use land efficiently and to protect useful lands from being taken up by other land use types like urbanization; the important role that land capability classification or land suitability classification plays for land use policy formulation and efficient use of the land ; and
- The significance that land capability/suitability classification has in putting land at different values for market for various purposes.
Considering some general factors such as environmental, economic and social problems observed in Ethiopia on the one hand, and the clear benefits of land use planning that would provide a sustainable development on the other hand, it is a paramount importance to have well studied land use planning. At present Ethiopia needs to have well organized and efficient land use planning technologies to be applied in both urban and rural land resources according to their applicability and degree of importance as justified below:
- Any development Planning must start and have information from land resource surveys and land evaluation
- Selection of priority areas for development (as for conservation) and suitable areas for various activities(as for irrigation, parks, infrastructure, etc.) needs the study of the intensity of the problems and the resources the areas have
- Decision for any development projects on the land needs assessing its impact on the environment
- Any land use change, if properly done, gets community acceptance
- The use of land resources, now a days, must guarantee the present as well as the future generation on a sustainable basis through proper use (conservation) resisting the challenges from resource depletion, degradation and pollution, which all need applying land use study and planning science.
In general Ethiopia, as one of the poorest nation in the world and with the highest rate of land resources degradation, has to take a step to avert the trend of land mismanagement by following proper land evaluation procedures; which this paper will contribute in finding the way for feasible input data generation.
The conventional methods in producing land use evaluation input data such as DEM and land cover information need large campaigns that result in land surveying teams using analogue or analytical techniques. In the last decades satellite image based topographical map production is turned into operational state from its experimental state. Recently many local scale landscape or topographical monitoring requirements are maintained by high resolution satellite images (Kanab 2002, Zomer et al. 2002, Baily et al. 2003, Su¨zen and Doyuran 2004a, b, Liu et al. 2004).
It is known that Land suitability analysis is the process of matching demand, crop requirement, and supply, the quality of the land. Where it is necessary to specify the type of specific land use (e.g for forest plantation, maize, rangeland, etc.) so as to match with crop requirement, basic land characteristics, such as depth of soil, climate, amount of pH, level of soil nutrient, depth to ground water, etc.. Thus the scope of this thesis is limited to generating parameters necessary for the land suitability analysis.
Despite ongoing research efforts on land-cover and land-use patterns, there remains a need for development of basic land-cover datasets providing quantitative, spatial land-cover information (Xavier and Szejwach 1998, Nunes and Auge 1999). Moreover, in recent years the scientific community has recognized that there is a gap in available land-cover information at regional and global scales for use in regional-and global-scale land-use modeling (Nunes and Auge 1999, Cihlar 2000).
Satellite remote sensing provides an important source of land-cover data; however, it is evident that improvements in image-processing methods to address the information requirements of land use capability classification research are crucial. These include:
Improvements in land-cover discrimination and change detection from remotely-sensed data, made more acute given new spatial resolution and multi-spectral datasets (Nunes and Auge 1999)
the development of rapid techniques for identification of hot spots or ‘critical zones' of change (Lam et al. 1998, Nunes and Auge 1999,Tucker and Townshend 2000) and to aid in scene and band selection from multi-spectral data (Lam et al. 1998, Qiu et al. 1999).
The development of automated techniques that are reproducible and that require a minimum of work from an analyst (Cihlar 2000), at the same time, the importance of understanding not only landscape structure but also landscape function points to the need for research on techniques that can describe the spatial configuration of landscapes and landscape changes (Nunes and Auge 1999).
This project is a one of the initiative to investigate the land cover and its respective slope deriving factor (DEM) of the study site and to recommend technologies applicable to the overall land cover study projects in the dry high lands of Ethiopia.
The study combines field verification and computer processing using state-of-the-art remote sensing and Geographic Information System (GIS) technologies. The study specifically applies and eexplore the potential of Visible and Near Infrared (VNIR) , and SWIR bands of the Advanced Space borne Thermal Emission and Reflection Radiometer ASTER images to discriminate land use categories where the land is fragile with mixed uses villages, patches of forest, patches of grazing land, crop land, wasteland, etc. the study will also explore the potential of ASTER images to provide stereo images for DEM generation of the scene that can be used to generate the Slope. The DEM generation task will investigate developing a rational function model. At last integration of the land cover and the DEM together with other GIS data can be used as input data to classify the suitability of land for specific land use.
1.2. Statement of the Problem
More than 63% of all smallholders in Ethiopia have less than 1 hectare of land. Population is growing rapidly and, although in the northern parts of the country the average rural population density is only 33 persons per square km, the population density per unit of arable land is much higher (138 persons per square km). Land fragmentation is common and the more fragmented holdings are, the more time it takes to manage them, with potential consequences for productivity. The national average is 3.2 parcels per smallholder, though districts averages vary from a little over 1 to more than 5. The broadest areas of high fragmentation are in eastern Amhara and Tigray, although there are also districts with high average fragmentation in Gambella, parts of SNNP, and the eastern highlands. (CSA, 2001/02)
As a result of fragmentation, farm sizes are very small and the use of fallow is rapidly disappearing, causing problems of declining soil fertility and erosion.
Population growth increases the demand for land and contributes to farming on steep and fragile soils, also leading to erosion problems. It increases demand for biomass as a source of fuel, leading to deforestation and increased burning of dung and crop residues, thus increasing the problems of erosion and nutrient depletion. Population growth increases demand for livestock products and therefore leads to increased livestock numbers, causing overgrazing and consumption of crop residues by animals.
In such situation Land degradation is a great threat for the future and it requires great effort and resources to improve. The major causes of land degradation in Ethiopia are the rapid population increase, severe soil loss, deforestation, low vegetative cover and unbalanced crop and livestock production. Inappropriate land-use systems and land-tenure policies enhance desertification and loss of biodiversity. The balance between crop, livestock, and forest production is disturbed, and the farmer is forced to put more land into crop production.
The government has envisaged long- and short-term strategies to reduce the pressure on land and land fragmentation. Among the short term strategies are providing technical and vocational training to the landless youth to enable them to find off-farm employment and encouraging emigration to urban centers and to other parts of the region for resettlement. These strategies recommended allocation and reallocation of land to be based on the land use classification to be done in detail study.
Understanding the current status of land use is very important and this project will come up with important elements of current land use study using remote sensing technologies to provide reliable information that help to prepare a complete land use plan.
To approach the growing problems of natural resource management, spatially explicit information about physical, biotic, and human factors must be available in a variety of geographic and temporal scales (USFWS 1976). Local planners and managers require detailed knowledge of the region for which they have responsibility as well as information on the regional, state, and national levels. Land cover data are essential at several scales.
Current land cover data are vital to many applications including: making basic habitat assessments, delineating specific vegetative communities, calculating soil loss, and evaluating water quantity/quality within and between watersheds.
Land use planning is a recent phenomenon in Ethiopia, especially to the rural parts. Even today one cannot confidentially say that modern land use planning is practical in the rural peasant holdings, except the traditional ways.
At national level the modern activity of land use planning was introduced to the country following the 1974 land reform in 1975. During this time the “Land Use Planning and Distribution Department (LUPDD)” was established under the Ministry of Agriculture (MOA) in 1977 with a mandate of establishing master land use plan and building national capability in land use planning upon which the development policies and plans were based.(MOA, 1985).
Later on in Sept., 1977 another institution for land use planning activity was established under the Ministry of Agriculture called Land Use Planning and Regulator Department (LUPRD) with the following terms of References (TOR) (Robert I Green, 1980):
- To carry out land use studies and to regulate land use for policy decisions;
- To carry out detailed studies of soil, hydrology, climate, physiographic features and to classify land for different land uses as for farming, range land, forestry, etc.;
- To regulate and control land uses and managements required for different land uses, in accordance with land use plans;
- To allocate land for government, cooperatives, peasants and other land uses;
- To register and map lands by usage types; and
- To facilitate and control land use studies and land uses in the country.
Following these pioneer activities land use planning was getting roots in to the country and applied step-by-step in the large government owned and assisted projects, private investments as well as in a number of urban land uses.
Land use planning is taking place in urban areas in a better base than in the rural parts partly due to the urgent need to use the scarce urban lands increasingly and to reduce negative impacts of the different land use types on the human and physical environment. It is also partly due to the relatively more available skilled man power in land use planning in the urban areas than in the rural areas that it is more practical here.
Today many of the big towns of the country are guided by master plans which are, more or less, based on land use studies and planning though details vary overtime and areas.
Similarly, recent development, even in the rural areas, is based on some sort of land use planning and studies though variations are observed in applications.
Though the above developments in rural and urban land use planning are observed, the Ethiopian land use planning also suffers from some critical problems needing improvements. These problems are acting as a trap against the effectiveness of land use planning in Ethiopia so far and now as indicated by Ermias Bekele and KNNS Nair (1986):
- Lack of effective land use policy and current land use plan at national level acting as a guide line and for land uses and managements needed;
- Absence/lack of data generated on the basis of homogenous resource units ready for the land uses;
- Problems in soil losses, livestock carrying capacity, and management practices' determination;
- Lack of Remote Sensing and computerizations for assisting land use planning activities;
- Lack of change monitoring and taking corrective measures against the negative situations from the changes occurred;
- Absence of effective institution specialized in land use planning for all sectors which prepares and guides land uses for the various uses;
- Absence or serious lack of public participation for land use planning activity at all; and
- Lack of plan evaluations and revisions, and impact analysis on the various land uses that should be followed by protective or corrective measures.
Land Use Change Paradigm
The purpose for which land is used in an area (areas) is not static but dynamic over time due to many factors. Land use change at any location involves either a shift to a different use or an intensification of the existing one (Mayer and Turner, 1998). Always we see land gains and loses to and from a given land use due to natural as well as human activities.
Therefore, this indicated potentially arable land needs to be quantified in terms of type of land use, production potential and amount of inputs. If land is in short supply the response of many societies with a choice is analogous to intensify the use or to extend out wards by “reclamation” (Simmons, 1993). The intensification and expansion lead to land degradation and also affect the adjacent land uses there. Factors leading to change in an existing land use are numerous and operate at various level over space and time, out of which the following are most influential ones:
Population growth- "Forces that drive land use changes are complex and act at various scales with differential rates of change. Among them, the most obvious are population growth and concomitant growth in demand for land use products, and infrastructural development". (J. Kaiser et al. 1995).The human population is growing fast which, in turn, increases up the demand for food. This accelerates problems of land degradation through cultivation of marginal lands, soil erosion, deforestation and overgrazing. Further more, variability in crop yields becomes more marked as more marginal areas are utilized, requiring more management techniques (D.A. Davidson, 1992). Therefore, population growth acts as a major factor for changing land use patterns in an area, no matter to the variation of its extent of effects.
Urbanization- It is also clear that urbanization is expanding towards the rural lands reducing cultivated size of lands. The development of new and more space requiring economic activities such as manufacturing, infrastructures, entertainment, etc. need more space than before accelerating outward urban expansions and then changing the former land uses at the fringes of the urban centers and even with in.
Land degradation and output decline- when farmlands are over cultivated and become less productive farmers are forced to shift to other places and use that land for some other purposes which results in land use change in the area.
Changes in land use policy- When governments change their policy over land use the emphasis they give also changes such as production maximization (efficiency), conservation and sustainability, etc. so that the purposes for which they use their lands also changes over time depending up on their policy emphasis.
Change in market demand for products: When the demand for products rises or collapses land users either extend their land size (when markets rise) or, reduce or to tally change their activity in to new land use type (when markets fail).
Technological changes- when the technologies applied in land use change the intensity and size of land for a given purpose also changes including inputs and management practices which brings land use change in the area.
Natural disasters- In some case also some natural disasters as volcanoes, earthquake, droughts, pests and diseases, etc. contribute their own share to change the existing land uses in an area. Then the people are forced to move to other better places, so that new land use develops there, or they change their use of land to a new land use type related to the new environmental situations.
The major factors acting behind the above land use problems existing in Ethiopia are the following, as discussed by FAO (1984):
- Lack of scientific information about the resources of the country in terms of size, quality and spatial distribution;
- The growing size of human and livestock population with its burden on the environment;
- The alarmingly expanding urbanization and its complex problems; and
- The diversification of land uses and the growth of land use conflicts as a result of their complexities.
Technological Challenges
Taking the above facts as starting points, further assessment and evaluation of the land use planning process indicated that there are other challenges to tackle concerning the utilization of remotely sensed technologies and Geographical Information system (GIS).
Land use and Land cover mapping using remotely sensed image data involves delineation of the constituent units. Such a delineation, however, is dependent on the wavelength region in which they are imaged and also the spatial resolution of the imaging sensor.
Coarse spatial resolution band is of little use in the context of Northern Ethiopian land use system. This is because land use heterogeneity is intricately complex. A typical farmer in North Ethiopia own a land size of less than one hectare and that piece of land is further partitioned to different land use types. Farmers allocate different land use systems not simply for diversifying their land use types, but also because they want to get the advantage of divergent micro relief, soil type, and hydrological diversities within short distances. So simply using of low resolution will let missing of most of the fine but important classes of land use types if we are working on areas colonized by man. On the other hand, if we are working, in the low land parts of Ethiopia, the topographic diversity is less and therefore we can have relatively bigger sizes of each land use type, which is adequate enough to be captured by coarse resolution bands.
Only a few years ago high-resolution satellite imagery was available to a limited number of government and defense agencies, who were utilizing such imagery using highly sophisticated software and hardware tools. The notion of widely available high-resolution satellite imagery that can be easily exploited seemed to be an unlikely reality that would not be realized in the near future.
With the turn of the century this dream is rapidly becoming a reality as the world of high-resolution satellite imagery is evolving in an unprecedented rate. Sub-meter satellite imagery is already available from a variety of commercial vendors, such as the IKONOS™ and QuickBird™ satellite sensors, in a variety of formats and processing levels.
While the satellite imagery industry has made a quantum leap in terms of resolution, data availability and quality, the available tools and paradigms to process such data into valuable user oriented information are lacking behind. Many of the available tools for processing satellite imagery are beyond the reach of most users: they still require a high level of technical expertise and are usually complex. Furthermore the challenge of providing users with robust and easy to use tools for extracting information from satellite imagery is a challenge yet to be met in many of the commercially available software tools. While the high-resolution satellite imagery industry has progressed considerably over the last decade in terms of resolution, quality and availability, the available tools and methodologies for fast and easy processing of high-resolution imagery still pose a major barrier for most users.
One of the primary barriers to a wider adaptation and utilization of satellite imagery was the sensor model. Sensor models are a key component in restituting the functional relationships between the image space and the object space, and are essential in image ortho-rectification and stereo intersection. Until recently, only physical sensor models were available to users. These models are rigorous and highly suitable for adjustment by analytical triangulation and normally yield a high modeling accuracy (a fraction of one pixel). Furthermore, in physical models, parameters are statistically uncorrelated as each parameter has a physical significance. Yet, from the user's point of view, the utilization of a physical sensor model poses some difficulties. One of the primary drawbacks of the physical sensor model is that its application requires explicit understanding of each of the physical parameters and a high level of expertise. Moreover, even with complete understanding of the physical sensor model, users are still faced with the challenging task of recovering the exterior orientation of the sensor using a set of Ground Control Points (GCPs). When no GCPs are available, users cannot recover the exterior orientation of the sensor and therefore unable to perform various mapping and data collection operations.(---)
The way forward
The above mentioned technological barriers can not be exceptions to Ethiopia actually it is even worse in many aspects. Research ideas that would compromise such challenges should have a better place in the list of planners, policy makers and other stakeholders. As mentioned in the previous sections, selection of the best imagery and processing procedure is crucial if the juvenile land use planning process in the country can be further upgraded.
With the introduction of generalized sensor models, this situation has changed considerably. Generalized sensor models, such as the usage of the Rational Function sensor Model (RFM) (Tao and Hu, 2001a), have alleviated the requirement to obtain a physical sensor model, and with it, the requirement for a comprehensive understanding of the physical model parameters. Consequently, the use of the RFM for photogrammetric mapping is becoming a new standard in high-resolution satellite imagery that has already been implemented in various high-resolution sensors, such as IKONOS™ and QuickBird™. This has led to various research efforts that have primarily focused on the correction of biases in the RFM parameters (Hu and Tao, 2002); (Fraser and Hanley, 2003), ortho-rectification (Tao and Hu, 2001b); (Ganas et al., 2002), and block adjustment (Grodecki and Dial, 2003).
Inspired by the advantages of the RFM and its capability to provide an open approach to photogrammetric exploitation of the commercial high-resolution satellite images, one of the purposes of this paper was to explore how the RFM could be further utilized for generating DEM from ASTER imagery.
1.3. Objectives of the Study
1.3.1 General objective
To demonstrate the feasibility of Advanced Space borne Thermal Emission and Reflection Radiometer (ASTER) imagery to provide base line data for land use planning for sustainable land management
1.3.2 Specific Objectives
Under the umbrella of the above general objective this research works to meet the following specific objectives:
Investigating discriminating power of ASTER Imagery in studying land cover in highly fragmented high lands of northern Ethiopia.
To develop rational polynomial function model to generate a DEM that will be further processed to develop slope information.
1.4 Significances of the study
This research has the following practical significances to the target area and other areas with similar problems:
- It provides evaluation procedures on land use planning processes and literature resource to those interested to conduct related researches in the field for the future.
- It provides useful alternative solutions to current image processing techniques applied in the country; and it indicates the potentially possible application areas of ASTER Imagery processing for the land use planning process in the region
Scope
This thesis presents a small watershed land cover map representing for the northern region of the country, and DEM generated in small watershed representing mountainous area of the region. It will provide information just beyond the local watershed by demonstrating feasibility of using selected satellite imagery for regional planning as well.
1.5. Organization of the thesis
This thesis has five chapters dealing with different issues of the study. The first chapter is an introductory chapter about the research as a whole while the second chapter is a literature review part discussing basic sciences related to the research.
The third chapter deals with the research methodologies used in the research and the natures of the study area. Chapter Four is part of the thesis dealing with the research findings and discussions on the study result implications.
Finally, the last chapter, chapter Five, is a conclusion and recommendation part where the summary of the whole research and solutions to avoid the identified problems are mentioned.
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