Page 98 - Çevre Şehir ve İklim Dergisi İngilizce - Özel Sayı

The use of Geographic Information Systems and Remote Sensing Technologies in
Combating Desertification and Erosion

In their study ‘Integration of remote sensing techniques for monitoring
desertification in Mexico’, Becerril-Piña et al. (2016) evaluated desertification
in a semi-arid region on the Mexican plateau with RS technologies. ‘Landsat
Thematic Mapper 5’ satellite images were used in the study, and radiometric
characterisation and calibration were performed on the data in order to
compare the variables selected for multi-temporal analyses and to find
changes in the land surface. Thus, the spectral radiance for each band was
converted to reflectance and high quality data was obtained. Atmospheric
correction was performed to reduce distortions caused by the atmosphere. All
these operations and analyses were carried out using the ATMOSC module
and Cos(t) model in the Idrisi TerrSet interface. Some indices were used to
assess the status and severity of desertification:
• Bare Soil Index (BSI): It is used to identify areas without vegetation cover
by analysing the reflectance properties of bare soil surfaces (Rikimaru
et al., 2002; Xiao et al., 2006). BSI is calculated with a combination of
Red, Blue, Near Infrared (NIR) and Shortwave Infrared (SWIR) bands:
BSI=(SWIR+Red) − (NIR+Blue) / (SWIR+Red) + (NIR+Blue) (2)
• Normalized Difference Vegetation Index (NDVI): The NDVI method
developed by Tucker (1979) to analyse and interpret the photosynthetic
capacity and health status of plants from satellite images is used. It is
calculated through the Near Infrared (NIR) and Red (Red) bands.
NDVI = (NIR−Red) / (NIR+Red) (3)
• Soil Adjusted Vegetation Index (SAVI): It is a vegetation index developed
to minimise soil brightness in the areas with poor land cover (Huete,
1988). It is used to improve the accuracy of vegetation measurements
in the areas with high sensitivity to desertification. It is calculated with
the soil brightness correction factor (L), which provides more accurate
results by minimizing the reflectance differences between near infrared
(NIR) and red (Red) bands and vegetation and soil.
SAVI = ((NIR − Red) / (NIR+Red+L)) x (1+L) (4)
• Desertification Difference Index (DDI): It is a tool used to measure and
assess the extent of desertification. The NDVI index is determined by
the Albedo index and the slope (K) of the line placed in the feature
space (Pan and Li, 2013).
DDI = (K × NDVI) – Albedo (5)
• Albedo: It is expressed as the ability to reflect the sun rays falling on
the land surface. The areas that reflect more sunlight such as snow and
ice are considered as 1, while the areas with dense vegetation such as
forests, and the areas that absorb more light such as dams, seas and
oceans are considered as 0.

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Special Issue / 2024