Large‐scale relationships between basin and riparian land cover and the ecological status of European rivers

Abstract

SUMMARY1 -The study of large-scale pressure-impact relationships involves questions of hierarchy and scales. Answers to these questions will help managers define priorities for action to achieve the 'good ecological status' required by the Water Framework Directive (WFD).The main objectives of our study were 1) to establish the relative impact of pressures that degrade ecological status, especially those caused by agriculture and urbanization, 2) to identify regional patterns in these pressure-impact relationships and 3) to evaluate the relative weight of the pressures acting at the basin and riparian corridor scales, and the possible buffering effect of riparian areas.2 -We developed large-scale models linking invertebrate indices of ecological quality to river basin and riparian land cover in France, Slovakia, Estonia and UK. Invertebrate indices, transformed to Ecological Quality Ratios (EQR), were taken from national monitoring networks. We based the models on Partial Least Squares (PLS) regressions at national and a hydro-ecoregion (HER) scales. The HERs provided a framework for grouping data in terms of natural river features and human activities.3 -The different national methods provided consistent results that indicated the hierarchy of pressures impacting river invertebrates at the European scale. The most salient result was that artificial land cover (e.g. urban and industrial sites) in the river basin represented the pressure with the most negative impact on invertebrate indices, in all countries and regions.Author-produced version of the final draft post-refeering, the original publication is available at Freshwater Biology, 55: 1465-1482. doi: 10.1111/j. 1365-2427.2010.02443.x 4 -The impact of agricultural land cover was more variable. Arable land had a smaller impact than urban areas, and it was even insignificant in some models. The impact of vineyards depended on the natural geographical context. The effect of pastures seemed to be related to the intensity of the livestock they carried. These results supported the concept of regional pathologies for river ecosystems, as land use and anthropogenic influences are closely linked to physical landscape features. The proportion of arable land in the river basin appeared to be a weak predictor of agricultural impacts by itself; the type of cultivation and intensity as well as the proximity to the river must be taken into account.5 -At the riparian corridor scale, the negative impact of artificial areas or arable land and the positive effects of forests and pastures were demonstrated in many regions. The protective effect of riparian forests against mixed agricultural and urban pressures was demonstrated in three regions in France. Riparian corridors appear to be manageable areas, and these results strongly support the idea of including their restoration in priority actions for achieving good ecological status.

Land Use

“…For example, the protective effect of riparian forests against mixed agricultural and urban pressures was demonstrated in three regions in France. Riparian corridors appear to be manageable areas, and these results strongly support the idea of including their restoration in priority actions for achieving good ecological status (Wasson et al 2010). However, in a nested hierarchy of landscape types, large-scale uses can constrain and even overwhelm smaller-scale processes.…”

Benefits of riparian forest for the aquatic ecosystem assessed at a large geographic scale

“…The index is sensitive to pollution (especially eutrophication) and to general degradation (including habitat alteration). For its application to large geographical scale analysis based on the national level datasets, see also Wasson et al (2010). For fish, a standard electrofishing protocol was carried out during low-flow periods (May-October) to collect information about fish assemblages in the monitoring network.…”

“…We assumed that for areas in which these factors are quite homogeneous, nutrient transfers are similar, and so are temporal patterns of concentration in water courses. The application of hydro-ecoregions as homogeneous spatial units for this kind of analysis has already been successfully demonstrated in several studies (Wasson et al 2010;Sauquet and Catalogne 2011;Gauroy and Carluer, 2011). Preliminary to the selection of survey sites, the main anthropogenic stressors to riparian forest fragmentation were explored over the entire river network to allow the detection of datasets homogeneous in stressor conditions.…”

“…In literature, large scale inferences of a significant relationship of riparian forest cover with biotic integrity are weakly quantified or show loose correspondence (Allan, 2004;Wasson et al, 2010;Arnaiz et al, 2011), often owing to the difficulty of retrieving accurate land cover data for the riparian corridor zone (Tormos et al, 2011). Here, we observed consistent responses to riparian forest cover in the selected datasets for nutrients and for biotic integrity indices.…”

Spatial Assessment of Water-Related Ecosystem Services to Prioritize Restoration of Forest Patches

“…The effectiveness of the riparian vegetation has been supported by many studies over the recent past (Gregory et al 1991;Allan 2004;Studinski et al 2012). The reforestation of riparian corridors should be one of the priority actions to improve the quality of waterbodies (Wasson et al 2010). However, just the presence of riparian vegetation does not guarantee such environmental services; more studies are required to explain how the provision of services is affected by the forest condition and characteristics.…”