عنوان مقاله [English]
In the recent decades, mismanagement, human activities and climatic conditions developed a new view of Iran ecosystems, called desertification. Life cycle assessment (LCA) is a method to construct environmental profile of production systems. That was developed by industrial instruments, but in recent years it is applied by agricultural production process as well. Today, it is acknowledged that land use should be assessed by LCA, but there is still no consensus on the parameters for assessment. In order to assess such land use impact, it is initially necessary to define the variables in the LCI. Once the inventory data is gathered, the LCI results have to be characterized in the impact assessment phase. The main framework of LCA is based on the "from cradle to grave" where we are able to evaluate environmental impacts truly from start point to the end. In this way, we can use the theory of LCA to assess desertification indicators and estimation of ecosystem resistance to this phenomenon. Thus, in this research an LCA approach was applied for estimate ecosystem susceptibility to desertification.
Materials and Methods
This research concentrated on the role of LCA to distinguish ecosystem susceptibility to desertification phenomenon. In this way, at first the land units were considered Ecoregions, the region with similar ecological and climatic characteristics, and six ecoregions has been identified. Then, based on Delphi methodology, six main factors were determined. These are aridity, landuse, wind erosion, soil erodibility, salinity, and vegetation density. To calculate aridity, FAO/UNEP aridity index (P/ETP) was used. The land use map was developed by ETM+ imagery data and distinguished six classes including; desert, bare lands, cultivated lands, settlements, rangelands and forest. A report of critical center of wind erosion prepared by KR organization of Natural Resources and watershed management was applied for wind erosion. Soil erodibility was calculated based on the Sepehr et al. 2014. Salinity and vegetation indices were calculated by spectural ratio of imagery data. To assess susceptibility degree a characteristic factor (CF) for each ecoregion has been calculated. One of the main contributions of this study is the establishment of desertification impact CFs for the ecoregion. The divisions between these areas are based on climatic and vegetative cover factors, both aspects having a major influence on soil desertification risk. Thus, after calculating CF for each ecoregion total characteristic factor was developed by geometric mean of each CF. Ultimately, the susceptibility degree to the desertification was evaluated and mapped.
Results and Discussion
The results indicated the high preference aridity and wind erosion at Khorasan Razavi province which is in relation to the climatic conditions and land use changes in the recent years. The greatest desertification risk is found in the moderate arid desert ecoregion, with a CF of 2.21. The susceptible ecoregions mainly covered more than 70% of the KR areas. In this case, the desertification impact of the activity should not be integrated in LCA studies. This can be used to identify those cases without desertification impact. The LCIA Desertification value is also zero when CFi or any other variable is zero. A value of zero for CFi means that the activity being studied is in an ecoregion with no desertification risk. The LCI Desertification value of the activity being assessed is determined by the addition of the individual values given to each of the sex variables, according to a scale of values. This paper provides CFs including desertification impact in LCA studies, and the variables suggested allow the comparison of the benefits and threats posed by different human activities.
In this research, an LCA methodology was developed for assessment of ecosystem susceptibility to desertification phenomenon. Main biophysical variables including aridity, wind erosion, landuse, erodibility, salinity, and vegetation density belong to the driving force, state and pressure frameworks. The desertification impact evaluation of any human activity in a LCA should include these common, basic four variables. The purpose of this research is to investigate desertification susceptibility degree of ecoregions at Khorasan Razavi as vulnerable province to land degradation and desertification in Iran. In this study, we applied Life Cycle Assessment (LCA) framework to assess susceptibility. In the first, an ecoregions map was provided by adjusted De-Marton climate index. Six main indicators including aridity, land use, wind erosion, soil erodibility, salinity, and vegetation cover were determined by Delphi methodology. The preference degree of each indicator was calculated using Entropy algorithm. Ultimately, we estimated characterization factor (CF) for each ecoregion. The layer integration was done using geometric mean with desertification susceptibility map. The results showed that the ecoregion of moderate arid desert is most susceptible to desertification.