Original Research ArticleLand-cover change dynamics and insights into ecosystem services in European stream riparian zones
Introduction
Human-driven modifications of the Earth's natural environment largely affect ecosystem structure and functions (Lambin and Geist, 2006, Sala et al., 2000). Among these processes, the transformation of land has been recognized as one of the main actors in the decline of the global environmental conditions (Foley et al., 2005, DeFries et al., 2004), and the major driving force for biodiversity loss (Vitousek et al., 1997). Changes in land-cover type are possibly the clearest and most informative indicators of a change in state and characteristics of the environmental systems (Robson and Berkes, 2011, Weber and Hall, 2001). For these reasons, systematic monitoring and assessment of land-cover dynamics are recognized as sources of highly relevant information for planning, conservation, and management of the environment (EEA, 2010b, Haines-Young and Weber, 2006, Gerard et al., 2010).
This study focuses on the analysis of change of European stream riparian zones. With this term we mean those transitional environments (ecotones) between terrestrial and freshwater ecosystems, whose abiotic and biotic conditions are influenced by the watercourse surface and subsurface hydrology (NRC, 2002, Verry et al., 2004). Riparian ecotones are of utmost importance for the maintenance of the biological connections between plants and animals, providing corridors for species dispersal in fragmented landscapes, and sustaining meta-population dynamics (Gillies and Cassady St Clair, 2008, Naiman et al., 1993). These environments currently play a prominent role as components of the European Green Infrastructure (European Commission, 2013, Sundseth and Silwester, 2009), which is a part of the new EU-wide Biodiversity Strategy to counteract continental biodiversity loss. Riparian zones are also primary actors in the reduction, through filtering and transformation, of non-point-nutrient and pollution sources (Zhang et al., 2010, Daniels and Gilliam, 1996, Zalewski et al., 2003), as well as providing bank stabilization against floods (Bennett and Simon, 2004). In other terms, the riparian zones are able to deliver a large series of ecological and societal services (Naiman et al., 2005).
Stream riparian habitats are recognized as among the most fragile environments (Nilsson and Grelsson, 1995). Being strongly connected to the surrounding landscape and the stream ecological processes, the conversion of natural land to artificial land-cover along rivers produces significant negative effects involving, among others, riparian corridor fragmentation (Décamps et al., 1988, Clerici and Vogt, 2013), loss of riverine transitional habitats (Tockner et al., 2008) and changes in species assemblages (Ferreira and Moreira, 1999). Riparian vegetation is especially sensitive to water availability (Carpenter et al., 1992), thus land-cover conversions affecting stream water, e.g. a change to intensive agriculture or dam construction, can seriously affect the riparian zones’ extension (Rosegrant et al., 2009, Poiani et al., 2000, Kondolf et al., 1987). Riverine floodplains in many European countries have already lost a very large part of their original extension, in some cases up to 95% (Tockner and Stanford, 2002). Historically, these ecological systems have been characterized by a very high rate of reclamation (Ravenga et al., 2000) and are considered especially threatened (Olson and Dinerstein, 1998, Tockner et al., 2008).
A major potential consequence of land-use change on natural systems is the direct alteration of their ecological integrity (Woodley et al., 1993). This concept is related to the maintenance and support of processes and structures that are necessary for the self-organizing capacity of ecological systems and their functioning (Barkmann et al., 2001). When land-cover conversion occurs, the ecological integrity can be strongly affected, and consequently the systems’ capacity to deliver goods and specific ecological/societal services (Burkhard et al., 2012), id est their capacity to provide ecosystem services (ES). The notion of ES is rapidly expanding in the scientific and decision-maker communities, since ecosystems were recognized as highly valuable capital assets supporting human welfare (Millennium Ecosystem Assessment, 2005, Daily, 1997). ES are also recognized as instrumental for the implementation of biodiversity conservation strategies and the enhancement of natural capital. For these reasons the ES concept was recently included in the Aichi Targets of the global Strategic Plan for Biodiversity at the 10th Conference of Parties of the Convention of Biological Diversity (CBD, 2010) and incorporated in the new European Union Biodiversity Strategy (European Commission, 2011).
The availability of a new pan-European riparian zone dataset developed by the European Commission Joint Research Centre (Clerici et al., 2013, Clerici et al., 2011) allowed to obtain unprecedented continental-wide statistics for a fully representative set of European stream riparian zones. This information coupled with continental land-cover change data could provide a large scale overview of the conversion processes taking place in these environments, together with an indication of the changes in their capacity to provide goods and services.
More specifically, the objectives of this study are to: (i) spatially detect the natural and semi-natural European stream riparian zones subject to land-cover change between 2000 and 2006; (ii) identify the major trajectories of conversion and the underlying driving forces; and (iii) derive a broad indication of the resulting change in their capacity to support ecological integrity and provide specific ecosystem services.
Section snippets
Data
The distribution of European stream riparian zones was derived from Clerici et al. (2013) dataset, hereafter RZ2000. The dataset considers river-floodplain systems and the riparian networks associated to minor and ephemeral watercourses of the continent. Functional riparian zones are also considered in the dataset and they are defined as those areas where no hydrological connection is detected, but their proximity to water highlights functional ecological connections with the stream system (
Land-cover trajectories and ESC change
The riparian zones involved in land-cover change processes extend over an area of 1552 km2. This surface corresponds to 1.8% of the estimated surface in the year 2000 for the same region (Clerici et al., 2013). Approximately 9.4% of change events (146 km2) are located within 50-years frequency floodplains, as derived from LISFLOOD data (Van Der Knijff et al., 2010). The density distribution of change events in riparian zones at continental scale is shown for illustration purposes using 10 km cells
Conclusions
This land-cover change study provided a continental overview of the conversion processes occurring in stream riparian zones at the European scale. The large majority of land-cover trajectories involved conversions between forest and transitional woodland-shrub, with forestry and fires as the main drivers of transformation during the period considered. Such trajectories are not unique to the riparian environments, since this result is in accordance with change statistics for the whole European
Conflict of interest
None declared.
Financial disclosure
None declared.
Acknowledgments
The authors would like to thank Nina Nygren e Juha Peltomaa (University of Tampere, Finland) for insightful discussions on land-cover dynamics. Dr. G. Bidoglio (EC-JRC) is strongly acknowledged for his constant support of this research. We would also like to thank Dr. G. Zulian (EC-JRC) for her support with cartographic issues and M.B. Dunbar (EC-JRC) for early revision of the manuscript.
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