Annotated Bibliography. GIS/RS Assessment of Desertification

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1 David Hussong NRS /14/2017 Annotated Bibliography GIS/RS Assessment of Desertification Desertification is one of the greatest environmental challenges of the modern era. The United Nations Conference on Desertification defined desertification as the diminution or destruction of the biological potential of the land, which could lead ultimately to the formation of desert-like conditions. (UNCOD, 1977) The desertification of land has the potential to displace populations, financially burden nations & private companies, and reduce food supply due to the degradation of agricultural land. Every year ~21 million hectares of land become economically unfeasible for crop production and ~6 million hectares of land are lost to desertification entirely (Shalaby et al, 2004) Desertification is increased by many natural and artificial pressures in a PSR framework (Pressure, State, Response). (Edoardo et al 2005) Soil health, salinization, draught, wind and water erosion are natural pressures that increase the response of desertification. Artificial pressures due to human activity include urbanization, deforestation, and poor land management. Climate change also affects desertification by altering environmental conditions which increases the response. Remote sensing is a powerful tool to collect data on desertification. Remote sensing has the advantages of covering a wide area in a more cost-effective way then could be achieved with field methods. Remote sensing also enables long term monitoring of land change. The size and movement of an active sand dune can be easily tracked over the years using Landsat data. (Elhadi et al 2009) Remote sensing also has the advantage of having historical records of land cover. Using historical data, such as Landsat data from the 90 s, modern scientists can compare current data and track the progress of desertification. Land use and agricultural land change can be identified remotely. Topsoil stability and change, an important indicator of desertification, can be identified remotely using Red, Blue and Green bands from Landsat TM and ETM+. (Albalawi & Kumar, 2013) Spot imagery has been used in countries such as Egypt to identify urban growth as the main source of loss of fertile land. Draught detection is possible by observing thermal bands. Erosion and changes in topography are observed and quantified using Digital Elevation Models. Analysis of remote sensing data is paramount to finding trends and observing changes in land cover. Geographic information system (GIS) is a powerful tool to synthesize data collected remotely, through fieldwork, or collected by census. Desertification can arise from a number of pressures. A Desertification Quality Index (DQI) is the combination of a soil quality index, a vegetation quality index, a climatic quality index, and a management quality index. (Ali & El Baroudy, 2008) GIS allows for these parameters to be modeled in raster format and to analyses the data in a meaningful way. Many desertification studies base the methods they undertake on the Mediterranean Desertification and Land Use (MEDALUS). MEDALUS relies heavily on remote sensing analyzed by GIS software in order to reproduce analysis such as normalized difference vegetation index (NDVI). Since

2 vegetation cover is a primary indicator of environmental stability, this is a powerful and quick analysis of environmental health that can be performed over a large area of land. In practice this index has a similar equation to: NDVI = (TM4-TM3)/(TM4+TM3) With TM4 being the Thematic Mapper band 4 on Landsat and TM3 being the Thematic Mapper band 3. (Elhadi et al 2009) Due to the availability of Landsat data both historical and modern, the NDVI is an exceptional tool for tracking the progress of desertification. In environments where vegetation coverage is not a primary indicator of desertification, such as hyper-arid environments, a Grain Size Index (GSI) can be used to identify the health and changes to the topsoil of an area. Choosing the correct analysis is important to the accuracy of the study. Preliminary understanding of desertification s pressures and responses in the area must be recognized before analysis can have meaningful input. Remote sensed data must be backed up with ground data in order to verify its accuracy. A GSI analysis should be coupled with soil sampled from the study area in order to infer the accuracy of the metric you are using. The goal of the study will also determine what analysis fits. Shalaby et al (2004) found that a classification system of cultivated land, non-cultivated land, and water provided a more in-depth view into desertification s effect on agricultural land in Egypt than the use of NDVI. Remote sensed images are subject to atmospheric corrections. This drawback, as well as the human error of the selection of the wrong analysis, is why field work is necessary to assure accuracy. As remote sensing technology increase new analysis will be possible. It is hypothesized that a red-edge spectral band will allow increased accuracy in areas with low vegetation. (Albalawi & Kumar, 2013) Desertification does not follow national boundaries and in order to combat loss of land, nations will have to work together for better land management policies.

3 Annotated Bibliography Albalawi, E. K. and L. Kumar Using remote sensing technology to detect, model and map desertification: A review. Journal of Food, Agriculture & Environment. 11 (2): This article serves as a review for the science of detecting and mapping desertification. The authors stress that understanding the causes of desertification in each case must be noted before choosing the correct analysis and sensing equipment. Desertification can occur due to a multitude of reasons natural and artificial such as wind erosion in highly arid, sandy environments, or mismanagement of land in agricultural situations. The review suggests that remote sensing is ideal for mapping and tracking desertification as it can cover a wider area while costing less than ground methods. Geographic information systems (GIS) can be used to synthesize remote data with ground data, such as soil samples, and census data, such as land management data. The authors review analysis indices such as normalized difference vegetation index (NDVI) and look towards the future of an additional Red-Edge spectral band as new technology that will improve plant studies in low vegetation cover areas. Albalawi and Kumar stress that remote sensing must be used in tandem with ground data in order to develop the full picture of the changes occurring in the environment. This need for both datasets arises from the corrective processes required for remote data. The data collected from remote sensing equipment must be verified by ground data to ensure accuracy. Elhadi, E. M., Nagi Zomrawi and Hu Guangdao Landscape Change and Sandy Desertification Monitoring and Assessment. American Journal of Environmental Sciences 5 (5): The authors of this paper are assessing land cover changes in northern China in regards to sandy desertification as the environment changes. These changes are pressured by increased population and increased agricultural development. While they found that fixed sand dune area decreased over the study period in Shaanxi Province, China, active sand dunes increased. The increase in active sand dunes is problematic as active sand dunes are mobile and increases desertification in the surrounding areas quicker than fixed sand dunes. Not only have known active sand dunes increased in size, new ones have formed as well. Desertification has increased rapidly in areas of agricultural land use for farming and grazing. The authors hypothesize that misuse and exploitation of the land in northern China, as well as wind erosion, accelerated the process of desertification. They draw these conclusions from the expansion of desertification at a rate above the average in farmland and the increase in active sand dunes. Ali, R. R. and A.A. El Baroudy Use of GIS in Mapping the Environmental Sensitivity to Desertification in Wadi El Natrun Depression, Egypt.. Australian Journal of Basic and Applied Sciences, 2(1):

4 The Wadi El Natrun depression is considered for agricultural development based on proximity to the Egyptian capital of Cairo and the presence of ground water. The Ali and El Baroudy implemented GIS using remote sensing data in order to qualify what areas, if any, of the Wadi El Natrun depression are suitable for farm development and what areas are sensitive to environmental degradation due to desertification. As reclamation of desert land for agriculture is an expensive process, it is important that the land is screened for the possibility that farmland will not be affected by desertification in the future. It is also important that the land is not so sensitive that mismanagement or development will not irreversibly damage it. Using a combination of Landsat ETM images, Digital Elevation Models, climate data and policy enforcement data the authors created a desertification sensitivity index map of the depression in order to find what areas can withstand development. An analysis of the data suggests that the northern area of the Wadi El Natrun depression is more suitable for development than the southern area. Shalaby A., M. A. Ghar, and R. Tateishi Desertification impact assessment in Egypt using low resolution satellite data and GIS. International Journal of Environmental Studies 61(4): The authors of this study are concerned with loss of agriculturally productive land to desertification in Egypt. Due to the relatively low amount of agricultural land in Egypt, found mostly around the Nile river, the loss and reclamation of fertile land is imperative to sustainable development of Egypt s infrastructure. The study compared two methods of identifying land loss and reclamation, the Normalized Difference Vegetation Index & and classification system. The authors found that classifying land in three categories: cultivated land, non-cultivated land and water, was a more useful approach in identifying the change in agriculturally rich areas. The government and private businesses have set up desert reclamation programs. This study found that while cultivated land grew approximately 25.8%, 11% of old agricultural land was lost. The authors point out that this land lost was highly productive Nile delta land while they reclamation efforts have reclaimed land that will need significant investment to provide the same productivity. Mismanagement of irrigation, the use of unfumigated fertilizers, and the cultivation of high nutrient/high water requiring crops are possible causes for the loss of land. While the governments efforts to increase fertile land in Egypt have been successful in terms of land cover, they have lost land that could have been preserved. Hadeel S., M. T. Jabbar and X. Chen Application of remote sensing and GIS in the study of environmental sensitivity to desertification: a case study in Basrah Province, southern part of Iraq. International Journal on Geomathematics 2: Sandy desertification is an extreme form of desertification due to the movement of sand dunes and wind erosion. The authors of this paper used remote sensing data in tandem with soil samples from the Basrah province of Iraq to provide framework for the use of GIS analysis of remotely sensed data to identify soil types and track sand movement. Unlike European Mediterranean environments, desertification in more arid environments such as Iraq is caused by wind erosion and salinization.

5 Identifying an increase in sandy soils, and where they are increasing, is paramount to understanding desertification in these arid and hyper arid environments. Soil samples taken throughout the region were used to provide evidence that the topsoil grain size index, based on red, blue and green spectral bands, correctly identified the nature of the soil. The authors point out that a large change in the Land Use/Land Cover (LULC) has occurred in vegetation land. The authors hypothesis that the increase of sandy soils in these lands is due to logging and development. Understanding where the changes in LULC are occurring is an important step in making decisions on a government level to combat the increase of desertification. I found the author s focus on identification and tracking desertification in order to implement engineering measures in order to combat desertification a step in the right direction as most papers focus only on the identification without providing practical solutions. Edoardo A.C., Costantini, M. Bocci, G. L Abate, A. Fais, G.Leoni, G. Loj, S. Magini, R. Napoli, P. Nino, M. Aolanti, L. Salvestrini, F. Tascone, F. Urbano Mapping the State and Risk of Desertification in Italy by means of Remote Sensing, Soil GIS and the EPIC Model. Methodology Validation on the Island of Sardinia, Italy. Experimental Institute for Soil Study and Conservation The authors of this study expressed the need for a more precise methodology and definition for delimitation of desertification prone areas and areas which have already become functionally sterile. They claim the United Nations Convention to Combat Desertification definition is defined to describe the phenomenon on a global scale and methodology used to identify desertification based on this definition does not present accurate data on national and local levels. This is supported by reviewing previous desertification studies which used global scale. One study reviewed showed only small areas of southern Italy and the islands of Sardinia and Sicily were at risk while a study using the more recent MEDALUS approach found the Alps and Po Plains were at risk but did not identify southern Italy. The authors synthesized multiple data bases including climate data, national soil data, Digital Elevation Models & Landsat TM images in order to draw a nationally focused land cover database. The authors stress that each tool used has limits. The NDVI analysis of vegetation cover provides a great overview of areas undergoing or at risk of desertification but cannot analyses the environmental health of land that has been used for agricultural. The use of different techniques in conjunction, as well as georeferenced field benchmarks, allowed the authors to create a more precise methodology for the identification of desertification on a smaller scale. This smaller scale is important in areas of environmental transition zones such as the Mediterranean where areas of desert are intermingled with land that is yet to be functionally sterile. Other references UNCOD, Round-up, plan of action and resolutions, United Nations Conference on Desertification (Nairobi, Kenya, 1977)