Existence of green areas in towns brings many positive effects. Those are in most cases external - they are not part of any market and their price is not explicitly known.
This is also the reason why the positive effects of greenery are not taken into account in decision-making involving green areas. Using methods for evaluating the environment, we are able to estimate the extent of the benefit which urban greenery provides to various subjects.
The confirmation of existence of these benefits and estimation of its magnitude may contribute to more sustainable development of towns.