Thresholds and reference conditions: moving targets in management

In REFRESH we will identify temperature, flow and nutrient/organic matter load thresholds for rivers for application in adaptation, mitigation and restoration strategies. Long-term biological, hydrological and physico-chemical data series will be analysed to determine if changes in ecosystem structure and functioning are occurring, whether these are linked to climate drivers and whether ecologically relevant thresholds can be identified (e.g. the transition from a permanent to a temporary system.)

This transition is already occurring in many European streams not only Mediterranean systems. The focus will be on functional indicators for this transition (linking to the EU project MIRAGE). We will evaluate whether reference conditions in selected river types are changing and whether this is linked to climate drivers. Reference conditions will be tested for climate vulnerability. We will develop a concept of dynamic reference conditions (moving targets) as part of WFD methodologies.

We will identify thresholds in lakes and acceptable ranges (per ecoregion) for

  1. temperature,  water level, nutrient/organic load and salinity;
  2. identify and quantify a climate change induced shift of ecological thresholds for the intercalibrated indicators along a nutrient gradient;
  3. determine changes in reference conditions due to climate change;
  4. define shifts in ecological thresholds on mitigation, adaptation and the restoration efforts needed to meet the WFD and HD objectives. 

Reference condition concept

Left: Idealised diagram illustrating decadal-scale change from the past to the future to show the response of a lake system to increasing and decreasing stresses and the potential change in targets for ecosystem recovery resulting from a change in the boundary conditions (e.g. climate) of the system.

FromBattarbee et al. 2005. Freshwater Biology, 50, 1772-1780. doi:10.1111/j.1365-2427.2005.01427.x


Ecologically relevant thresholds and reference conditions will be identified for riparian wetland functioning and biodiversity using literature reviews, analyses of long-term biological, hydrological and chemical data series. We will up-scale experimental results using improved meta-data analysis techniques, to identify thresholds and reference conditions and assess whether these will change in the future. The focus will be on responses of algae, macroinvertebrates and macrophytes. Experiments will be used to obtain new data on thresholds, including a study on biogeochemical functioning of Mediterranean riparian wetlands, which are highly vulnerable to climate changes but play a key role nutrient retention at the landscape level. A pilot study will be undertaken to examine whether sedimentation in riparian zones is sufficient to reconstruct past riparian zone vegetation and reference vegetation types.