Disturbance and the role of refuges in mediterranean climate streams
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MEDITERRANEAN CLIMATE STREAMS
Review paper
Disturbance and the role of refuges in mediterranean climate streams Belinda J. Robson • Edwin T. Chester • Bradley D. Mitchell • Ty G. Matthews
Received: 8 February 2012 / Accepted: 22 October 2012 Ó Springer Science+Business Media Dordrecht 2012
Abstract Refuges protect plant and animal populations from disturbance. Knowledge of refuges from disturbance in mediterranean climate rivers (medrivers) has increased the last decade. We review disturbance processes and their relationship to refuges in streams in mediterranean climate regions (medregions). Med-river fauna show high endemicity and their populations are often exposed to disturbance; hence the critical importance of refuges during (both seasonal and supraseasonal) disturbances. Disturbance pressures are increasing in med-regions, in particular from climatic change, salinisation, sedimentation, water extraction, hydropower generation, supraseasonal drought, and wildfire. Med-rivers show annual cycles of constrained precipitation and predictable
seasonal drying, causing the biota to depend on seasonal refuges, in particular, those that are spatially predictable. This creates a spatial and temporal mosaic of inundation that determines habitat extent and refuge function. Refuges of sufficient size and duration to maintain populations, such as perennially flowing reaches, sustain biodiversity and may harbour relict populations, particularly during increasing aridification, where little other suitable habitat remains in landscapes. Therefore, disturbances that threaten perennial flows potentially cascade disproportionately to reduce regional scale biodiversity in med-regions. Conservation approaches for med-river systems need to conserve both refuges and refuge connectivity, reduce the impact of anthropogenic disturbances and sustain predictable, seasonal flow patterns.
Guest editors: N. Bonada & V. H. Resh / Streams in Mediterranean climate regions: lessons learned from the last decade
Keywords Climate change Drought refuge Flow regulation Intermittent rivers Refugia Salinisation Sedimentation
B. J. Robson (&) E. T. Chester School of Environmental Science, Murdoch University, 90 South St, Murdoch, WA 6150, Australia e-mail: [email protected]
Introduction
B. D. Mitchell Research and Graduate Studies, University of Ballarat, University Drive, Mount Helen, VIC 3350, Australia T. G. Matthews School of Life and Environmental Sciences, Deakin University, PO Box 423, Warrnambool, VIC 3280, Australia
In 1999, Gasith and Resh identified the role of disturbances created by seasonal sequences of flooding and drying as crucial processes structuring mediterranean climate streams and rivers (med-streams and med-rivers). They identified several anthropogenic disturbances that particularly affected these rivers: water extraction, flow regulation, salinisation,
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Hydrobiologia
and pollution. Knowledge of refuges in med- and semi-arid streams and rivers has increased during the last decade, perhaps in
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