ABSTRACT
How can we estimate the value of the ecosystem services? Costanza et al. (1997) have found the value by adding the costs of all the services that we utilize by ecosystems: purification of air and water, recycling, recreational
services, and natural resources such as timber, fish, drinking water, and so on. All activities require energy that can do work. Services by ecosystems mean activities offered to the user of ecosystems and they could therefore be measured by the work energy. This means as the total amount of eco-exergy (work capacity), that an ecosystem offers. The sustainability of nature (ecosystems) can also be expressed by the work capacity, because
1. Sustainability in the Brundtland’s sense means that the same level of ecosystem services must be maintained for the future generation.
