Expert models are a novel modelling approach in order to evaluate the impact of agricultural practices on biodiversity. These models are based only on the knowledge of some biological characteristics of animal or plant species and only on field observations and biometric measurements to build a database. An expert model that predicts plant species presence in any herbaceous ecosystem has been developed. This model is based on a database of 17 life traits or biological characteristics already identified in the literature for 2912 plant species. In order to predict the presence probability of grassland plant species, the information of the traits and characteristics was aggregated with data on farming practices and environment factors by fuzzy logic associated with an expert system. This model allows predicting a list of plant species with their patrimonial value, without realizing floristic site-inspection This model approach has been the first concrete application of functional groups theory based on life traits of plant species to predict plant presence according to human activities and environmental factors.