The 4th Esri Eastern Africa Education GIS Conference 23 – 24 September, 2016 |UNCC, Africa Hall | Addis Ababa, Ethiopia Detecting and Quantifying Land Use/Land Cover Dynamics at the Wadla Delanta Massif, Northcentral Highlands of Ethiopia Nahusenay Abate PhD in Soil Pedology and Land Evaluation Samara University, Ethiopia
INTRODUCTION Various types of land covers are formed by either natural or human or both factors over the last centuries (FAO, 2006). The effects of natural processes and human interventions are facilitating ecosystem changes as the whole and land use/land cover (LU/LC) changes in particular. Some of the factors cause directly like forest destruction and others merely enable the action of the former.
Continued ... Introduction Natural effects of LU/LC dynamics may be over a long period of time. For instance, climate change, Whereas the effects of human activities are being immediate and often radical (Vlek, 2005) These changes cause great environmental uncertainty for : • local and regional climate change, • biodiversity loss, On the other hand, Farmers of the area do not use any cultural • soil degradation and and/or chemical treatments to • pollution of water, soil and air. reclaim and maintain soil fertility
Continued … Introduction The rate, extent and intensities of human pressure on land are absolutely greater than the previous time which affects status, properties and functions of ecosystems (Ellis and Pontius, 2007). LU/LC changes are a dynamic and complex phenomenon occurring within the interface between human and ecological systems All these have: • a significant influence on natural ecological functions , • a contribution of desertification and • the global climate change (Lambin, et al., 2003; Varallyay, 2010).
Continued … Introduction Population pressures sedentary accompanied with agriculture, settlement and sociopolitical instability have resulted in: • substantial deforestation, • loss of biodiversity and • undesirable changes • low agricultural productivity and • food insecurity One of the major factors limiting agricultural development in Africa in general and Ethiopia in particular is the lack of information on land use and land characteristics .
Continued ... Introduction Topography also modifies the spatial variability of soil physicochemical properties, soil water relationships, soil textural composition, soil forming processes and their interaction with variable conditions (Tan et al., 2004)
Introduction … One of the immediate challenges facing in Ethiopia today is land degradation , particularly loss of vegetation cover, soil quality and fertility as well as soil erosion. As with respect to geopedological approach, this can be related to three levels, namely: • landscape, • relief form, and • landforms ( Prasad and Govardhan, 2011 ). Topography can affect: • the potential land use systems through long term soil formation and short term seasonal effects; • soil nutrients through controlling soil water budgets, soil erosion and deposition (Tsui et al., 2004 and Kumhalova et al ., 2008)
Objective of the Study The general objective of this study was, therefore, initiated to address the limited LU/LC change information in this region of the country at the Wadla Delanta Massif of northcentral highlands of Ethiopia The specific objective: To detect and quantify the spatial and temporal land use/land cover dynamics at the Wadla Delanta Massif
Location and Size of the Study Area The study area is found at the Wadla Delanta Massif northcentral highlands of Ethiopia which is located at: • 11 ° 23 ’ 30.74 ’’ to 11 ° 50 ’ 52.45 ’’ N latitude and • 38 ° 58 ’ 30.30 ’’ to 39 ° 27 ’ 44.78 ” E longitude • which was mainly situated in plateau areas • Altitudinal ranges from 1500 to 3819 meter above sea level (masl) at the bottom of the valleys (Gosh Meda) and the tip of the mountain (Mekelet), respectively. It is placed about: • 499 km to north of Addis Ababa, and • 98 km to northwest of Dessie town, South Wello Zone
F 1. igurLocation map of the study area
Geomorphology and Topography of the Study Area The major landforms of the study area comprise: extensive plateaus with numerous convex hills, chains of hills with mountainous ridge, oval in shape with dendritic drainage pattern, river-valleys and very deep gorges at the boundary.
General Location …
MATERIALS AND METHODS For this study, different datasets were organized and used from satellite imageries and topographic maps. • ERDAS Imagine 10.0 and ArcGIS 10.2 software were utilized. • Moreover, recently updated 1:50,000 topographic map was scanned, geo-referenced and merged. • additional point information and linear features (contours, roads and rivers) were utilized. The Acquisition dates were chosen to be as closely as possible in the same cropping season and from comparable climatic conditions .
Data Sources & Materials … Table 1. Satellite Image Data Data type Sensor Acquisition date Spatial Path/row resolution 57 × 57 meter Landsat MSS 1973-01-31 168/52 30 × 30 meter Landsat TM 1995-01-05 168/52 ETM + 30 × 30 meter Landsat 2014-01-21 168/52
Data Sources & Materials … • In parallel to the remote sensing work; field work was carried out to collect data for Ground Control Points (GCPs). • The field data were collected by measurements. During these field trips, both GCPs and the Area of Interest (AOI) of study area were selected, demarcated and measured by Global Positioning System (GPS). • To evaluate the accuracy of the classification system, 1020 reference test pixels were identified and confusion matrix was used. Confusion matrix indicates the nature of the classification error. • The accuracy assessment was performed for the 2014 LU/LC map which was adopted by a stratified random sampling method.
Social Survey Methods In this study, structured and semi-structured questionnaire interview were administered to households living within the study area. The participants were taken from all topographic positions (upper, middle and lower elevations). A total of 40 key informants were interviewed. They were nominated by the District Administrations who are the ordinary farmers who lived in the area for longer period and had historic background about the area. Moreover, the District Agricultural Office Experts and development agents were incorporated in this study.
RESULTS AND DISCUSSION • The results of the study revealed that the forest and grazing land covers over the years showed irregular trends (i.e. decrement and increment trends), • As compared to the three consecutive periods (the 1973 ’s, the 1995 ’s and 2014): • From 1973 to 1995, the forest and grazing lands showed for the decrement trends but the agricultural lands increment, whereas • from the 1995 to 2014 the trends showed that the forest and grazing lands increment and the agricultural lands decrement. • The increment of the forest land by 0.2%. This changes might be due to the plantation program of Ethiopia over all the country.
Continued … Results & Discussion … • The shrub land showed that for all the three consecutive years, regularly the decreasing trend, The bare land and riverbed ( barren land ) showed frequent increment for all the consecutive years. The increment of bare land and riverbed from 1973 to 1995 were by 36 and 43%, and from 1995 to 2014 by 39 and 10% , respectively.
Results & Discussion … For the last four decades, the barelands/open spaces were increased by 88% and riverbed by 5 7% of the total area (Table 3). This causes might be due to • subsequent cultivation and • the occurrence of repeated drought • accompanied with unwise use of land resources , which led to degradation of significant area of land
Table 3. Area coverage of LU/LC classification (1973-2014 ) 1973 1995 2014 Land use/cover Area Area Area km 2 km 2 km 2 Category % % % Agriculture 356.97 33.78 375.92 35.57 345.37 32.68 Grazing land 89.81 8.50 53.12 5.03 80.95 7.66 Forest land 42.01 3.98 2.80 0.26 4.93 0.47 Shrub land 368.54 34.87 353.35 33.44 256.28 24.25 Bare land 181.78 17.20 246.32 23.31 341.56 32.32 Riverbed 17.67 1.67 25.27 2.39 27.69 2.62 Total 1056.78 100 1056.78 100 1056.78 100
Landsat-MSS image of land use/land cover in 1973 The 1 st Landsat image false color composite before processing; The 2 nd Landsat classified subset image; and The 3 rd Area coverage and percentage of land use/land cover
Landsat-TM image of land use/land cover in 1995
Landsat-ETM+ image of land use/land cover in 2014
Extent, Trend and Rate of LU/LC Change The results of the LU/LC analysis indicate that, in all the periods, bare/open space and riverbed areas showed an increasing trend, while the rest showed decrements in area coverage. For the first time span period (1973-1995), the cultivated, bare and riverbeds showed an increment, while the rest showed decrements. In the second time span (1995-2014), except for agriculture and shrub lands, the rest showed increments
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