The national literature on forest ecosystem valuation is scarce and little is known about how important the valuation of forest ecosystem services and their internalization in low density regions of Portugal are. Hence, there is a need for technicians, academics, and researchers to mitigate this knowledge gap through further research in this area. The chapter is a literature review with the objective of systematizing and synthesizing the knowledge produced in the period between 1992 and 2021 with regard to estimates of the economic value of forest ecosystem services in Portugal as well as finding evidence that relates the mechanisms of internalization of externalities in the sustainable development of low-density regions. A meta-regression was estimated, and the results indicate 220 international dollar/hectare/year in 2019 (190 euros/hectare/year) for forest ecosystem services in Portugal. Payment mechanisms for non-market forest ecosystem are still at an embryonic stage, which does not allow an accurate measurement of their real contribution to the sustainability of low-density regions.