Hydrobiologia (2013) 719:383–425 DOI 10.1007/s10750-012-1333-4 MEDITERRANEAN CLIMATE STREAMS Review Paper The effects of land use changes on streams and rivers in mediterranean climates Scott D. Cooper • P. Sam Lake • Sergi Sabater • John M. Melack • John L. Sabo Received: 26 March 2012 / Accepted: 30 September 2012 / Published online: 2 November 2012 Ó Springer Science+Business Media Dordrecht 2012 Abstract We reviewed the literature on the effects alterations of land use, vegetation, hydrological, and of land use changes on mediterranean river ecosys- hydrochemical conditions are similar in mediterra- tems (med-rivers) to provide a foundation and direc- nean and other climatic regions. High variation in tions for future research on catchment management hydrological regimes in med-regions, however, tends during times of rapid human population growth and to exacerbate the magnitude of these responses. For climate change. Seasonal human demand for water in example, land use changes promote longer dry season mediterranean climate regions (med-regions) is high, flows, concentrating contaminants, allowing the accu- leading to intense competition for water with riverine mulation of detritus, algae, and plants, and fostering communities often containing many endemic species. higher temperatures and lower dissolved oxygen The responses of river communities to human levels, all of which may extirpate sensitive native species. Exotic species often thrive in med-rivers altered by human activity, further homogenizing river Guest editors: N. Bonada & V. H. Resh / Streams in communities worldwide. We recommend that future Mediterranean climate regions: lessons learned from the last decade research rigorously evaluate the effects of manage- ment and restoration practices on river ecosystems, S. D. Cooper (&) Á J. M. Melack delineate the cause–effect pathways leading from Department of Ecology, Evolution and Marine Biology, human perturbations to stream biological communi- University of California, Santa Barbara, CA, USA e-mail: [email protected] ties, and incorporate analyses of the effects of scale, land use heterogeneity, and high temporal hydrolog- P. S. Lake ical variability on stream communities. Australian Centre for Biodiversity, School of Biological Sciences, Monash University, Melbourne 3800, Australia Keywords Mediterranean rivers Á Streams Á S. Sabater Land use Á Ecosystems Institute of Aquatic Ecology, University of Girona, 17071 Girona, Spain S. Sabater Introduction Catalan Institute for Water Research (ICRA), 17003 Girona, Spain Profound and far-reaching impacts of humans on the environment are mediated through land use changes J. L. Sabo School of Life Sciences, Arizona State University, which destroy, degrade, and fragment habitat, and Tempe, AZ, USA constitute the primary cause of losses in biodiversity 123 384 Hydrobiologia (2013) 719:383–425 worldwide (Sala et al., 2000; Chapin et al., 2001). rivers in med-regions. Furthermore, we conduct Human impacts on landscapes often diminish the comparisons to determine if land use effects on stream capabilities for ecosystems to provide essential ser- and river ecosystems are different in med and non-med vices for people, including clean air and water and systems, particularly given the large seasonal and natural products (Foley et al., 2005). Land use changes interannual variability in rainfall, runoff, and stream have had a large effect on terrestrial and aquatic discharge observed in med-basins, and end with environments in mediterranean climate regions (med- research recommendations (Gasith & Resh, 1999). regions), that is the Mediterranean Basin, California- Baja California, southwestern Australia, southwestern South Africa, and central Chile, because of their long The history of land use change in mediterranean history with human activity, rapid urban and agricul- regions tural development, and large climatic and topographic variation (Underwood et al., 2009; Sirami et al., 2010). Humans have a long history with areas now occupied Because med-regions contain many endemic species, by med-ecosystems. Some of the earliest hominids human impacts on these regions have a disproportion- occurred in South Africa and early African Homo ate effect on global biodiversity and make mediterra- species expanded into the Mediterranean Basin nearly nean ecosystems (med-ecosystems) among the ‘‘most a million years ago, with European populations imperiled’’ in the world (Myers et al., 2000; Horwitz following the retreat and advance of glaciers. From et al., 2008; Underwood et al., 2009). Although its African origins, Homo sapiens expanded through considerable research has been conducted on the Europe and Asia, eventually reaching Australia by effects of land use change on terrestrial environments 40,000–60,000 years ago and the Americas by about in med-regions, studies of land use impacts on aquatic 12,000 BP (Fagan, 2003; Hassell & Dodson, 2003). habitats are more limited. Because water is seasonally Early human populations in med-regions engaged in scarce in med-regions, many rivers and streams have hunting, fishing, and gathering activities, up to the time been dammed or diverted to provide water supplies for of European conquest in the Americas, southern human activities (Gasith & Resh, 1999). Given the Africa, and Australia. Early hunter-gatherers in med- critical importance of water quality and quantity in regions affected landscapes primarily by burning med-regions and concerns about the impacts of human vegetation, but also by harvesting wood and maintain- environmental alterations on aquatic systems and ing paths and wells, creating a mosaic of patches in species, there is a need for more data and knowledge different successional stages after disturbance (Simo- to guide management and policy decisions balancing netti & Cornejo, 1990; Keeley, 2002; Abbott, 2003; human and environmental needs for sustainable water Arnesto et al., 2010; Bowman et al., 2011; Faivre et al., resources. Research in other temperate regions of the 2011;Gammage,2011; Neumann et al., 2011). Further- world has shown that land use changes denude native more, the Khoisan in southwestern South Africa vegetation, increase runoff and erosion, alter stream focused on livestock husbandry beginning about geomorphology and substrata characteristics, modify 2,500 years ago, and the Mapuche of central Chile flow regimes, and enhance the transport of nutrients, became small-scale farmers *1,400–2,000 years ago, sediment, and contaminants from catchments to with both using fire to create pasture or farmlands. receiving waters, all with numerous implications for Although many med-regions originally contained the stream and river biota (Paul & Meyer, 2001; Allan, extensive tree stands, frequent fires started by native 2004; Walsh et al., 2005; Johnson & Horst, 2010). peoples apparently destroyed and prevented the re- Human land use impacts on med-ecosystems are establishment of forests and, in extreme cases, even predicted to be heightened by climate change which shrubs, promoting the expansion of grasslands and will result in warmer, drier, and more variable weather degraded scrub (e.g., Acacia caven Molina savanna in (Klausmeyer & Shaw, 2009). Chile, garrigue in the Mediterranean Basin) (Keeley, In this article, we review and synthesize the 2002; Gammage, 2011). These people created more literature on land use impacts on mediterranean rivers open terrain which facilitated European settlement in (med-rivers) to provide a foundation for evaluating Australia, South Africa, and the Americas (Hallam, current and predicted human effects on streams and 1975; Timbrook et al., 1982; Gammage, 2011). It 123 Hydrobiologia (2013) 719:383–425 385 appears that ancient land use practices are reflected in Current land use patterns and changes today’s landscape patterns (Keeley, 2002), with many in mediterranean regions areas continuing to be subjected to intensive livestock grazing or agricultural, mining, urban, and/or indus- Human population growth and land use changes have trial development. greatly altered landscapes in med-regions. Average The most intensive and complex impacts of ancient human population density ranges from 5 people/km2 humans on landscapes occurred in the Mediterranean in Australia to ca. 50 people/km2 for Chile and South Basin. Originally, much of the Mediterranean Basin Africa to ca. 120 people/km2 in the Mediterranean was covered by pine, oak, and cedar forests; however, Basin and 250 people/km2 in California-Baja Cali- the expansion of human settlements and agricultural fornia (Underwood et al., 2009), with urban density activity *5,000–2,000 years ago resulted in declines exceeding 200 people/km2 in southern Europe and in forests and the expansion of shrublands and over 2,000 people/km2 in the Los Angeles River grasslands (Hooke, 2006). These changes in native basin, California (Table 1). From 1990 to 2000, vegetation occurred at different times in different human population density and urban area increased places, with the Minoans deforesting Crete by by 13% and agricultural area by 1% in med-regions 1200–1500 BC with later, similar changes in ancient throughout the world, with the greatest proportional Greece, where sacred groves were protected. Land use changes for population density occurring in Chile changes accelerated during the expansion of the (19%) and for urban and agricultural expansion in the Roman Empire, resulting from the local use of forests Mediterranean Basin (?17% change in urban