Biodiversity provides various ecosystem services to human societies and addresses human needs, but human interventions have caused biodiversity loss and reduced ecosystem services. The designation of protected areas is a strategy to manage environmental crises and biodiversity loss, but these areas are under threat. This research analyzes the factors affecting biodiversity loss in in protected areas using a quantitative methodology (descriptive-correlational). Data were collected through structured interviews, using a questionnaire, with 250 out of 5095 rural households of the local communities of the Sorkhabad Protected Area of the Zanjan Province. The sample size was calculated using the Cochran sampling formula and was randomly selected through the multi-stage sampling technique. The questionnaire was developed by the research team and its questions’ content and face validities were assessed and verified by an expert panel in this field. The reliability of the research instrument was also confirmed by conducting a pilot study and applying the Cronbach’s alpha test. The results showed that the biodiversity loss is determined by the variables of local community participation, interventions by external organizations, human drivers related to local communities, the livelihood, motivation, and knowledge of local communities, attitudes towards biodiversity conservation, knowledge about biodiversity degradation, knowledge about biodiversity challenges, and knowledge about ecosystem services, which explained 68 percent of biodiversity loss variance. Therefore, it is necessary for decision-makers and policy-makers to pay attention to relevant and effective factors in reducing the loss of biodiversity in order to conserve and restore ecosystems and species in protected areas.