Using Remote Sensing Data to Assess the Effects of Drought on Range Ecosystem:
 A Case Study from Qazvin Region, Iran

Ali Akbar Nazari Samani¹ & Saied Lotfi²

¹Faculty of Natural Resources, University of Tehran, Karaj, Iran
e-mail: aknazari@ut.ac.ir

²Senior Expert of Agricultural Climatology, University of Tehran, Iran

Abstract

Drought is one of the most effective factor and predominant natural disasters causing land degradation in arid and semi arid regions. According to United Nation Convention to Combat Desertification (UNCCD) desertification is the consequent of climate changes and human factor. In comparison to other natural disaster, based on frequency, severity, period, socio-economics damages and long term effects, drought has dedicated high rang to itself over past decades.

In this research on the basis of climatic data and field observation the effects of drought on vegetation cover and land degradation were assessed trough remote sensing techniques and geographic information system. After geometry and radiometric correction as well as principle component analysis vegetation indices (VI) were extracted from satellite image of ETM+ detector. According to correlation coefficient between ground truth and VI, NDVI was employed to extract vegetation cover density map truth classification methods in both wet and dry periods.  The results of special and quantitative changes in vegetation cover were determined over 1987, 1998 and 2001 years to distinguish the critical area of vegetation cover changes during dry period. In each region the changes in vegetation cover were calculated to estimate the decreasing in forage production and tolls. Results indicated that drought had a sever effects on forage production and vegetation cover and consequently caused to accelerate degradation processes such as erosion which conduced socio-economic problems. Among vegetation classes, the regions with high density vegetation cover had a dramatically decrease in vegetation cover (up to 40%). According to results it can be implied that to decrease the effects of drought in rangeland utilization it will be more safety to planning on by-products like medicine plants which are less susceptible to drought that vegetation cover.

Keywords: Drought, Impact assessment, Remote sensing, Vegetation index, Rangeland, Iran