Land Use and Land Cover Change Analysis Using GIS and Remote Sensing in The Case of Kersa District, Jimma Zone, Oromia Region, Ethiopia

Background: Land use and land cover change is driven by human actions and also drives changes that limit availability of products and services for human and livestock, and it can undermine environmental health as well. Therefore, this study was aimed at understanding land use and land cover change in Kersa district over the last 30 years. Time-series satellite images that included Landsat 5 TM, Landsat 7 ETM + , and Landsat 8 OLI/TIRS, which covered the time frame between 1990-2020, were used to determine the change in land use and land cover using object based classication. Results: The object based classication result revealed that in 1990 TM Landsat imagery, natural forest (16.07%), agroforestry (9.21%), village (12.03%), urban (1.93%), and agriculture (60.76%) were identied. The change result showed a rapid reduction in natural forest cover of 25.04%, 9.15%, and 23.11% occurred between (1990-2000), (2000-2010), and (2010-2020) study periods, respectively. Similarly agroforestry decreased by 0.88% and 63.9% (2000-2010) and (2010-2020), respectively. The nding indicates the increment of agricultural land, village, and urban, while the natural forest and agroforestry cover shows a declining trend. Conclusions: The nding implies that there was a rapid land use and land cover change in the study area. This resulted in loss of natural resource and biodiversity. Overall, proper and integrated approach in implementing policies and strategies related to land use and land cover management should be required in kersa district.


Background
Land use and land cover change (LULCC) ; Also known as land change) is a general term for the human modi cation of Earth's terrestrial surface. Though humans have been modifying land to obtain food and other essentials for thousands of years, current rates, extents and intensities of LULCC are far greater than ever in history, driving unprecedented changes in ecosystems and environmental processes at local, regional and global scales. These changes encompass the greatest environmental concerns of human populations today, including climate change, biodiversity loss and the pollution of water, soils and air (Ellis, 2007). Time series analysis of land cover change and the identi cation of the driving forces responsible for these changes are needed for the sustainable management of natural resources and also for projecting future land cover trajectories (Giri et al., 2003). Therefore, available data on land use and land cover (LULC) changes can provide critical input to decisionmaking of environmental management and planning the future. Determining the effects of land use and land cover change on the earth system depends on an understanding of past land use practices, current land use and land cover patterns and projection of future land use and land cover, as affected by human distribution, economic development, technology and other factors (Thadiparthi andMekonnen Aregai, 2011, as cited in Abiy, 2014). Detecting land use change over time has become increasingly important consideration for environmental management (Kiswanto and Mardiany 2018;Mensah et al., 2019). Therefore, studying the rate of LULCC support a decision making processes. Due to world population boom and advancement in science and technology, the natural resources are overexploited for the sake of economic activities with high severity in developing countries. Agricultural expansion into the forest land, timber logging, charcoal production and re wood harvesting are the major drivers of deforestation in Africa (Declee et al., 2014;Muhati et al., 2018).
Changes in LULC can alter the supply of ecosystem services and affect the well-being of humanity (Rimal et al., 2019;Deng et al., 2013;Olson et al., 2008). The LULC has the potential to in uence the biological processes, and alter the provision of ecosystem services (Gibson et al., 2018;Geng et al., 2015;Kishtawal et al. 2010). The change in LULC has an impacts on hydrological uxes (Guzha et al., 2018), regional climate (Geng et al., 2015;Costa et al., 2003), agricultural production (Deng et al., 2013) and greenhouse gas emissions (Furukawa et al., 2015;Findell et al., 2007). In addition, it is also one of the factors for local environment disturbance by in uencing runoff, soil loss, stream ow, and (Cheruto et al., 2016).
Due to rising population over the years, lots of pressure has been imposed on the land resources in Ethiopia where approximately 85% of the populace engages in agriculture. As a result, the shortage of arable land has led to expansion of cultivation into the water margins of rangelands, deforestation and decline of grassland as a result of overgrazing, charcoal burning and other unsustainable land uses. These actions have far reaching implications on the integrity of natural resources and ecosystems in the country.
LULCCs has also taken place in Kersa district, Oromia region over the years. Land has been subjected to a lot of pressure due to over-reliance on its resources. There has also been rapid population growth in the county in the recent past and this has translated to over-utilization of land and its resources. Most communities are farmers and they therefore depend on land for their livelihood well-being and sustenance. This has resulted to the locals engaging in other sustenance activities such as charcoal burning, logging and even sand harvesting, all of which result to environmental degradation. Therefore, attempt was made in this study to map out the status of land use land cover of Kersa district, Oromia region between 1990 and 2020 with a view to detect the land changes that has taken place using remote sensing and GIS. The objectives of this study were to: (i) to identify and map the extent of LULC change over a period of 3 decades, (ii) to understand changes in land use and land cover occurring in Kersa district based on analysis of remotely sensed data, and (iii) to determine the nature, rate and location of land use and land cover change.

Location and relief
The study was undertaken in Kersa district, which is one of the district in the Jimma Zone of the Oromia Region of Ethiopia. It is bordered on the south by Dedo district, on the southwest by Seka Chekorsa district, on the west by Mana district, on the north by Limmu Kosa district, on the northeast by Tiro Afeta district, and on the southeast by Omo Nada district. The coordinate values that extend from 7º40'25"N to 7º56'35" N and Page 4/17 36 º54'10"E to 37º10'20"E covering a total area of 103001.34 km 2 (Fig. 1). The altitude of this district ranges from 1740 to 2660 meters above sea level and covers slope range from at (0º) to very steep (71º  (Landsat-5 TM 1990, Landsat-7 ETM + 2000and 2010, and Landsat-8 OLI/TIRS 2020 with 30m spatial resolution were used for the LULC change analysis of the studied district. Details of the images characteristics are tabulated in (Table 1). Landsat data were downloaded free of charge from U.S Geological Survey (USGS) Center for Earth Resources Observation and Science (EROS) (https://earthexplorer.usgs.gov/). All images were geometrically corrected and acquired in level 1T (L1T).
Except for Landsat image of the years 1990 and 2020, the time gap between the satellite images was more than 16 days, because of cloudiness. Images were classi ed into ve LULC classes; namely natural forest, agroforestry, village, urban and farmland (Table 2). In 1990, the highest extent of land use and land cover from all classes was agricultural land, which covers an area of 62,581.8 ha, contributes (60.76 %) of the total area. Natural forest and village (rural settlement) land cover an aerial size of 16,557 ha (16.07 %) and 12,386.3 ha (12.03 %) respectively, whereas the aerial coverage of agroforestry and urban was 9,488.9 ha (9.21 %) and 1,987.3 ha (1.93 %) from the total area of the district (Fig. 2 and Table 3). As indicated in (Fig. 3 Table 3) the greatest share of land use and land cover from all classes was agricultural land, which covers 65,453.9 ha (63.55 %) above half of the total area of the district. Village and settlement covers 12,703.9 ha (12.33 %) and 167.31 ha (17.50%), respectively. The least area was covered by agroforestry and urban, which was 9,967.97 ha (9.68%) and 2,465.01 ha (2.39%) from the total size of the study area. Agriculture still covered the largest area in 2000, which depicts conversion of other land cover classes to cultivated land.
By the year 2010, the areal coverage of agricultural land, urban and rural settlement increased by 66,035.8 ha (64.11%), 2,685.83 ha (2.61%) and 13124.6 ha (12.74%), respectively. Statistical data shows that the coverage of natural forest and agroforestry area decreased by 11274.8 ha (10.95%) and 9880.29 ha (9.59%), respectively. The growth of agriculture was due to the conversion of forest and agroforestry to agricultural land because of rapid population growth in the study area. In addition to this there was an expansion of urban and rural settlement (village) in 2010 due to population growth.
In 2020, the coverage of natural forest and agroforestry were decreased by 8,669.34 ha (8.42%) and 3566.79 ha (3.46%) while the coverage of agriculture, urban and village (rural settlement) were increased to, 69,959.7 ha (67.92%), 5,573.34 ha (5.41%) and 15,232.1ha (14.79%), respectively. The analysis of LULCC, we found that the farmland increased rapidly while natural forest and agroforestry were decreased more than half over the last 30 years in the study area (Figure and and Table ). The nding of this study is consistent with other studies carried out by Negassa et al., (2020)

Change detection of LULC in the district
The conversions of one LULC category to another between 1990-2000, 2000-2010, and 1990-2020 periods are presented in (Tables 5, 6 In the 1990-2000 period, 3074.54, 715.21, 8804.81, and 64.89 ha of agricultural land were converted from natural forest, agroforestry, village and urban area, respectively. This shows that agricultural land was gained from other LULC categories, a signi cant area of agricultural land were also reverted to natural forest, agroforestry, village, and urban area (Table 5). During these time, some area of village was also converted from natural forest (485.1 ha), agroforestry (146.59 ha) urban (22.59 ha), and agriculture (8908.74 ha).
Similarly urban land was gained from Natural forest (56.47 ha), village (347.53 ha), agroforestry (69.47 ha), and agriculture (91.45 ha) Although it is a small proportion, 5, 3 and 1 ha of village area was also in reverse converted to natural forest, agroforestry, urban, and agricultural land, respectively. Gains and losses in natural forest and agroforestry were also taken place during these periods (Table 5). In the second study period, 2000-2010, similar pattern has been observed as the rst one, the area of agricultural land increased to11274.84 ha although its area simultaneously was lost to natural forest (37.97 ha), agroforestry (518.8 ha), village (8634.68 ha), and urban (750.15 ha) ( Table 6). The most important contributors to the increase of agricultural land were village (8276.31 ha) and agroforestry (1601.46 ha). During 1990-2020 periods which span over thirty (30) years and estimates the current state of the LULC change. During these periods, 6357.42, 1507.77, 743.85, and 227.34 ha of natural forest were converted to agricultural land, agroforestry, urban and village, respectively. About 6717.11, 863.55, 350.17, and 188.91 ha of agroforestry were also converted to agricultural land, village, natural forest and urban area, respectively.
Similarly, urban and village were also gained from other LULC categories (Table 7). In these periods, a signi cant area of agricultural land were converted from village (8028.08 ha), agroforestry (6717.11 ha), natural forest (6357.42 ha) and urban area (82.58 ha). In reverse, there was also a considerable conversion of cultivated land to other categories. A signi cant amount of gains in urban and village area were also occurred in these periods (Table 7). of agricultural land and agroforestry as it is explained in the change matrix of ( Table 8). From (1990From ( to 2000 4146.5 ha of natural forest had been changed to agricultural land. Between 2000-2010, 1135.7 and 87.7 ha of natural forest and agroforestry had been changed to agricultural land respectively. This shows that there was an expansion of agricultural land within the speci ed time period because of population pressure and poor land administration.  , the rate of change indicates that urban, agriculture, and village classes were increased 119.53ha/year (180.45%), 245.93ha/year (11.79%), and 94.86ha/year (2298%), respectively. While natural forest and agroforestry shows a continues decreases in the study period (Table 8).

Conclusion
The study has clearly indicated there was a signi cant amount of LULC conversions had occurred from 1990 to 2020 periods in the study area. Agricultural land, village, and urban areas had been increased in the period of 1990 to 2020. In contrast, natural forest and agroforestry had been decreased in coverage.
Avoiding clearance of natural forest and agroforestry through awareness. In addition, proper and integrated approach in implementing policies and strategies related to land use and land cover management should be considered. Enhancing productivity using proper technologies needs to be induced to minimize expansion of agriculture into forest lands.

Declarations
Ethics approval and consent to participate Not applicable.

Availability of data and materials
The three Landsat images were downloaded from USGS) Center for Earth Resources Observation and Science (EROS). Primary data were also obtained through eld works and depth discussions with local elders which were selected from local community and agricultural development agents and.
Consent for publication I have agreed to submit for Environmental Systems Research and approved the manuscript for submission.

Competing interests
Not compete for interest.

Funding
The study was not funded by any organization Authors' contributions Not applicable.

Figure 1
Location map of the study area.