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Rivers ecosystems are characterised by running water (lotic habitats) while lakes ecosystems by standing waters (lentic habitats). The interfaces between water bodies and their catchment, including riparian zones, floodplains, and lakeshores are also an important part of the freshwater ecosystem.
Extent and change:
In the EU-28, the extent of freshwater ecosystem was assessed to comprise about 1.3 million km of total river length, 84,000 km2 of lake surface, 297,000 km2 of riparian land, and 367,000 km2 of potentially flooded areas. Notably, this includes only consideration of main rivers, whereas small streams are missed. Despite seasonal changes, the extent of rivers and lakes in Europe has been stable since the 1980s (Pekel et al., 2016); this is confirmed by CLC accounting layers that report about 108,000 km2 of rivers and lakes for the period 2000, 2006 and 2012.
Drivers and pressures:
Generally, human pressures on freshwaters due to over-exploitation (e.g. water abstractions) and nutrient pollution are still very high. Most pressures acting on freshwaters are due to processes that are moderately to highly stable, and changes in response to policies take time to become apparent. Several pressures have declined in the EU-28 since 2000, however in most recent years the improvement rate has slowed down, so that pressure trends in the 2010s remained mostly stable (Table 3.6.3). Land take in potentially flooded areas has continued in the last two decades. This is worrying for the critical role of natural riparian areas for pollution retention, flood attenuation, erosion control, habitat provision, and surface and ground water connectivity. With regards to pollution and nutrient enrichment, improvements are seen mostly with regards to domestic emissions and atmospheric nitrogen deposition
Convergence of evidence
Trends of pressures on rivers and lakes were calculated using 13 indicators. The assessment reveals that in the short-term trend, no indicator shows negative change resulting in degradation, six no change, one a positive change resulting in improvement, and six are not available or unresolved. In the long-term trend, no indicator shows negative change resulting in degradation, three no change, four a positive change resulting in improvement, and six indicators remain unresolved or have no data. Trends of condition of rivers and lakes were calculated using 23 indicators. In the short-term trend, no indicator shows further degradation or improvement, three show change, and 20 indicators remain unresolved. In the long-term trend six indicators indicate improvement, five show no change, and one degradation. 11 remain unknown (unresolved or no data).
In the EU a comprehensive water policy to protect water resources and aquatic ecosystems has been in place since 2000, when the Water Framework Directive entered into force. The WFD is a pioneering legislation as it includes ecological targets and addresses the complexity of pressures affecting the status of aquatic ecosystems (Carvalho et al., 2019). The legislation requires the development of River Basin Management Plans (RBMPs) containing Programmes of Measures (PoM) to reduce the significant pressures and achieve the Good Ecological and Chemical Status for all water bodies. The PoM should include also measures foreseen by other policies that protect the environment and regulate specific sources of pollution. As most pressures on aquatic ecosystems derive from human activities, the sustainable use of water resources and the protection of freshwater ecosystems imply trade-offs between different uses of water and require coordination between objectives of economic development and environmental protection. RBMPs are instruments to ensure the coherence and integration of water policy with other sectoral policies and measures, such as the agricultural policy. However, governance dynamics at the administrative and river basin levels have to be integrated
Water is a key resource for society, necessary for multiple uses. However, land-based human activities produce pressures that affect natural water availability and quality, modify riparian habitats and alter the abundance and composition of plants, fish and micro-organisms living in the aquatic environment. In the river basin, water is at the end of the pollution cascade. Sectoral demands for water, diffuse pollution from agricultural land, spread of invasive alien species, extension of artificial areas in riparian land, pollution of emerging substances from urban land, and climate change put freshwater ecosystem under multiple pressures that need to be addressed in integrated River Basin Management Plans. Overall, the ecological status of rivers and lakes is at least good in 39% of water bodies. Yet, the EU Habitats Directive data show that most freshwaters protected habitats are still in poor conditions in relation to freshwater biodiversity. The indicators collected for rivers and lakes indicate that while some pressures have decreased, showing some effectiveness of policy implementation, the level of anthropogenic pressures on aquatic ecosystems remains high, thus hindering the recovery of ecosystems. Major knowledge gaps remain in assessing current rivers and lakes condition across Europe and changes over time in pressures linked to climate change, chemicals and biodiversity issues, and on the response of ecosystems to multiple pressures. Policy is in place in the EU to protect and restore water resources and aquatic ecosystems. In the light of these chapter findings, there appear to be scope for immediate actions on recovery of riparian habitats, which could strengthen synergies between the WFD and Habitats and Birds Directives.