In May 1997, Nature magazine published 'The value of the world's ecosystem services and natural capital' (Costanza, d'Arge, de Groot, Grasso, Hannon, Limburg, Naeem, O'Neill, Paruelo, Raskin, Sutton & van den Belt). This summarizes efforts during the 1980's and 90's to give economic value to services provided from ecosystems.

In simple terms this means the monetary value contributed by a piece of natural ecosystem compared to for example a paved parking lot. This includes for example water conservation, flood control, and wildlife habitat. Wastewater recycling systems are not precisely comparable with ecosystems described in the article, as wastewater systems are basically human-manipulated agricultural lands.

However, just as constructed wetlands mimic many of nature's wetlands, so wastewater recycling facilities replicate many natural functions. Unlike monoculture farming, wastewater recycling facilities use integrated methods to replicate functions of wetlands, forests and grasslands.

Therefore by making conservative comparisons with the statistics in this work, it is possible to estimate equivalent values per hectare of ecosystem services provided by wastewater recycling facilities. Researchers identified services and values at US$ 6,600 for a one ha. site. Detailed calculations on this are available in the European Commission publication, 'Guide to Wastewater Recycling in Tropical Regions', referenced in the homepage.