The scientific literature suggests that the best unit to assess ecosystems is the 'socio-ecological system (SES)' (Gallopin, 1991, Glaser, 2008). SES integrates ecosystem functions and dynamics as well as human activities and the interactions of all these. The SES is equivalent to the SNA's institutional unit. Considering the production of ecosystem services, and in particular provisioning services, SESs are more or less homogenous. A large forest is at the same time a socio-ecological system with its own behaviour and a unit of production of timber and most other ecosystem services. A small forest that is part of a mosaic landscape with agriculture, villages and natural areas is certainly a production unit for timber, but.
