biodiversity impact assessment of tehran- pardis highway on two protected areas : khojir and sorkhehesar

human activities often adversely affect natural landscapes and ecosystems. natural landscapes consist of habitats, and habitat loss and fragmentation are major threats to biodiversity. environmental impact assessment (eia)as a systematic and well documented procedure to identify, describe and assess the direct and indirect effects of a developmental project in different environments does not comprise a well – developed method for quantifying and predicting impacts of ecosystem loss and fragmentation on biodiversity. in this context, this paper is dealt with the environmental impacts of tehran – pardis highway project on biodiversity of two protected areas, khojir and sorkhehesar that are located in tehran province in iran. two type of impact were considered in the assessment, the direct loss of ecosystems and the fragmentation on ecosystems. for computing ecosystem – loss, a space- occupation buffer was estimated for road layout and the ecosystem- loss impact was computed by over laying such a buffer map with the ecosystem map. the expected result of this stage was represented by a table showing project alternative project (in this study with and without project), and the estimated loss in area caused on each ecosystem type. furthermore, three patch indicators were selected to predict the effects of fragmentation: core area, isolation and disturbance. these indicators were used as indirect measures to describe the ecosystem viability. viability can be defined as the capability of an ecosystem to preserve its integrity and to accommodate its original biodiversity. finally, above mentioned impacts were predicted and for valuing ecosystems as a part of impact assessment procedure, rarity of each ecosystem was computed. the ratio between actual cover and potential cover of each natural ecosystem type were selected as indicators to express ecosystem's rarity. consequently, by applying this methodology, the biodiversity assessment approved the construction of tehran – pardiss highway.