Impact of alien grasses on the environment, biodiversity and crops in Iran

The high number of alien grasses in Iran makes it necessary to prioritize species for mitigating their negative consequences on the environment and agricultural production. We classified 34 alien grasses in Iran based on the IUCN Environmental Impact Classification of Alien Taxa (EICAT-IUCN) to assess their risks on native species and mapped their distributions in Iran’s ecological zones. We also discussed their impacts on agriculture and management options. Rottboellia cochinchinensis, Paspalum distichum and Microstegium vimineum have the potential to cause massive impacts, while Cenchrus longispinus, Eragrostis curvula, Panicum repens, Paspalum urvillei, Cortaderia jubata and Phyllostachys reticulata can cause major impacts on native species. Competition, transmission of disease and ecosystem structural impact accounted for over 49% of the mechanisms leading to environmental impacts. The Fisher's exact test indicates a significant association between the EICAT-IUCN score and life cycle. Of the 23 grasses invading crops, 60% have infested rice fields; and P. repens, P. distichum, Paspalum dilatatum and Leptochloa chinensis have the highest potential impact on yield losses (>60% in some cases in worldwide). P. distichum and P. repens can have the greatest potential impacts on both the environment and agriculture. Conservation priorities must be established to address the potential environmental impacts caused by alien grass species in Iran.