reference assessment is a direct and quantitative consultative method for analyzing perceptions, knowledge and associated value of ecosystem services demand or use (or even social motivations for maintaining the service) without using economic metrics. It could also be used to understand which ecosystem services are perceived as the most vulnerable, or which make the greatest contribution to human wellbeing. Data is collected through surveys using a consultative approach with different variations, such as free-listing exercises, ecosystem service ranking, rating or ecosystem service selection. It is generally used with an emphasis on individual perceptions (but collective preferences could be also gathered).
