Despite being an important concept to assess vulnerability of ecological systems, the literature is still unclear on how to measure resilience in different systems and therefore on how well the concept of resilience translates into the practice of analyzing the vulnerability of social systems. This paper presents a practical procedure to assess the degree of resilience of socio-ecological systems which builds on system dynamics analysis, in particular on loop polarity analysis. It shows that socio-ecological systems lose resilience when they exceed certain thresholds in which dominant polarity of their feedback structures shifts sign. Copyright © 2012 System Dynamics Society.