Ecosystem service evaluation of streams for nutrient and bacteria purification in a grazed watershed

The importance of sustainable development of
river systems based on ecological and socio-economic criteria is widely recognized. The "Integrated Valuation of Ecosystem Services and Tradeoffs" (InVEST) model, an ecosystem based model which
couples biophysical and economic models, is used to
examine the nutrient and bacteria mitigation processes
in the ungauged grazed area draining to the
Gulf of Kalloni, a semi-enclosed bay in Lesvos,
Greece. Point sources and grazing land loads are neglected
by the InVEST model, leading to poor estimation
of nutrient loads at this site. We include additional
terms to account for these sources. We also
apply climate change scenarios to assess their likely
impact on nutrient export and hydrology over the
drainage area. We show that the nutrient mitigation
capacity is currently exceeded in four sub-basins
with a compensation cost of up to 20 million dollars
over a 20 year period.