Human activities are putting pressure on rivers and streams—polluting them and altering their flow regimes. These changes threaten freshwater biodiversity. As a result, biodiversity in stream ecosystems is declining, although scientists still debate how widespread and severe the loss really is. In our project, we are working with researchers and stakeholders from four European countries to answer questions such as: How is biodiversity of invertebrates (small animals living underwater, like insects, crustaceans, and snails) changing across Europe? How much water does a river need, and how clean should it be to protect its biodiversity?
We are analyzing long-term data on stream invertebrates from across Europe to understand how the length and resolution of these time series affect our ability to quantify the magnitude and direction of changes in biodiversity. We are also comparing sites that are in a process of degradation with those that are recovering. The biodiversity trend analyses will be used to improve our understanding of how important pollution and altered flow regimes are for ongoing biodiversity changes. So far, we have found that detailed, high-resolution data are essential for accurately measuring both the direction and magnitude of biodiversity changes. Less detailed data might still correctly show the general trend but are less reliable for estimating the magnitude of changes in biodiversity. Preliminary results also suggest that the magnitude of biodiversity decline or recovery, and sometimes even direction, depend strongly on the biodiversity status at the start of the time series (the first point in time). For example, if a biodiversity monitoring time series started at a point in time where the biodiversity status was heavily degraded, a recovering trend may appear as stronger, because even minor improvements become more visible. Therefore, it is important to consider how the time series data are pooled, as combining time series data from many different sites could produce a range of differing biodiversity responses.
We also have established a model that predicts pollution loads of approximately 2,000 unique toxic contaminants based on registered land use activities. The model provides a European map that comprises predicted pollution loads for each areal unit (100 x 100 km). Next, we will link these to the biodiversity timeseries to identify when biodiversity starts to change along the gradient of pollution load. Furthermore, we are analyzing developments of flow regimes across more than 1,000 streams in Denmark to explore how we best can characterize flows that may be critical for stream biodiversity. These results will help us understand how to define “safe operating spaces” (SOS) - thresholds for water quality and quantity that freshwater ecosystems need to stay healthy. Finally, we’re working closely with stakeholders to understand how the SOS concept can support water management and policy decisions. This is how we will achieve the final goal of our DESTRESS project: To provide science-based tools that help balance the needs of freshwater biodiversity with those of human society.
Growing human demands for clean freshwater and climate change put increasing pressure on river ecosystems, but riverine biodiversity needs for freshwater quality and quantity are not quantified. DESTRESS is a synthesis project with the overall objective to provide guidance and knowledge to balance freshwater needs between riverine biodiversity and human society. DESTRESS is spearheaded by the Aquatic Synthesis Research Centre (AquaSYNC) and will synthesise and analyse unique and comprehensive time series of European riverine macroinvertebrate monitoring data (>2,000 sites across 23 European countries; 1968-2020, average 15 years of sampling) to identify temporal trends in ecological and biological trait composition, abundance, and common biodiversity metrics.
Temporal biodiversity trends will also be linked to simulated hydrological regimes for a subset of the sites and to existing European data on measured contaminant exposure to analyse pressure-response relationships and identify biodiversity change points along the existing gradients of hydrological and contaminant stress. The pressure-response relationships will be applied to define 'safe operating spaces' (SOS) for riverine biodiversity in context of their water quality and quantity requirements.
Through co-creation processes with key stakeholders, the concept of SOS will be applied to relevant case study examples to understand management, end-user, and legislative requirements for the SOS concept. These inputs will be embedded into the SOS concept of DESTRESS ensuring that the end-product will become operational, relevant, and will fit to legislative requirements for end-users, managers, and competent authorities. The end-product of DESTRESS will enable evidence-based decision making on freshwater consumption, supply, and treatment to balance water quantity and quality needs between freshwater biodiversity and human society.
