07/05/21 - Séminaire (en ligne) de Claudia WIEGAND
Excess nutrient load, low oxygen levels or siltation not only impair aquatic ecosystems by decreasing their biodiversity, but also complicate drinking water abstraction or restrict recreational activities, thus causing direct and indirect economic losses. The project CPES (Channel Payments for Ecosystem Services) develops PES schemes remunerating the farmer for activities improving water quality by reducing emissions of nutrients (both, nitrogen and phosphorus, P) or silt from agricultural activities. Catchment wide approaches are tested in 6 case studies at both sides of the channel.
One of the 6 case studies concerns Lac au Duc, suffering from recurrent cyanobacterial blooms. Long term data series were evaluated to follow nutrients entering the lake and climate conditions, connecting them to the observed cyanobacterial dynamics, as their inter-annual variance seems to increase. The main driving factor for cyanobacteria development is excess P, of which the sources in the lake’s catchment are merely of farming origin but vary according to hydrogeological characteristics and agricultural practices between the sub-catchments. While P reduction is the most efficient measure, this requires time, therefore the possibility to apply curative actions was assessed and hydrogen peroxide selected to be tested – with limited success. Long term prevention possibilities to ameliorate agricultural practices include e.g. permanent cover or anti-erosive hedges. We are now in the process to merge the monetary needs of the farmers to ameliorate their land management to the motivation of potential buyers to construct PES contracts, which may follow other interest such as carbon footprint. This project requires thus a multi-facetted approach combining expertise of ecology, hydrogeology, agro-economy, moreover the experiences of intermediate and farmers’ associations, and non-the-least, the agricultural skills of the farmers!