Climate change and European rivers: An eco‐hydromorphological perspective

Abstract

Climate change is expected to modify temperature and precipitation patterns throughout Europe, leading to warmer drier summers; wetter, milder winters; and an extended growing season. Alterations to feedbacks between important eco‐physical structuring processes driven by climate change may modulate river morphology, floodplain characteristics, and their biological communities. Current understanding is reviewed and synthesised to explore the potential responses, mechanisms, and ramifications of climatic shifts for the European riverscape. Fundamental drivers of change are expected to be (a) disturbance deviation beyond the historical norm and (b) vegetation morphodynamics, a key river process where ecological and fluvial‐geomorphological attributes interact to shape the physical environment. Increased seasonal temperature, summer drought, and winter flooding may affect the colonisation, growth, and mortality of plant species with consequences for riverscape structure and function as succession patterns adjust with repercussions for hydraulics and sediment dynamics. Such opposing winter and summer climate regimes are likely to impact vegetation patch dynamics, reflected in an increasingly variable patch mosaic as disturbance intensity deviates further from historical background conditions. How changes to climate drivers manifest themselves in individual river systems will also be affected by attributes such as catchment topography, geology, vegetation type, and previous human alterations. Where large scale change occurs, it will have consequences for the type and function of biological communities inhabiting the riverscape. Conventional engineering responses to meteorological disturbance will amplify the effect on river biota by reducing their ecological resilience, highlighting the need for a management response that integrates ecological and societal benefits simultaneously.

Effects of climate change on the life stages of stream‐dwelling brown trout (Salmo trutta Linnaeus, 1758) at the rear edge of their native distribution range

“…Reductions in reproductive habitat and periods in winter and spring could compromise the viability of trout populations more than expected from previous studies which only considered extreme warming in summer. On the other hand, hydromorphological alterations will also influence the response of rivers to climate change (O'Briain, 2019; O'Briain, Shephard, & Coghlan, 2017), which may already be evident in strongly altered rivers of humid‐temperate Europe (O'Briain, Coghlan, Shephard, & Kelly, 2019) and is expected to be even worse in rivers of southern Europe. Legacy effects of human modification are likely to have a big effect on thermal response given the widespread extent of alterations in Europe (Schinegger, Trautwein, Melcher, & Schmutz, 2012) and, consequently, in cold‐water species such as brown trout.…”

Biogeomorphology, quo vadis? On processes, time, and space in biogeomorphology

“…Fluvial and riparian environments have long been a focus area for biogeomorphological research, with several reviews (e.g. Bätz et al ., 2015; Politti et al ., 2018; Polvi and Sarneel, 2018; O'Briain, 2019; Viles, 2019) and special issues (e.g. references in Coombes, 2016; Picco et al ., 2017; Thoms et al ., 2018) available.…”

The efficacy of riparian tree cover as a climate change adaptation tool is affected by hydromorphological alterations

“…Predicted increases in drought and flood intensity are liable to be met by greater human intervention in both river flow regime and morphology, in the form of intensified flow regulation and engineering for flood prevention (Vaughan et al, 2009). The ecological resilience of stream biota to climate change disturbance will be affected by these and previous anthropogenic alterations of river systems (O'Briain, 2019;Timpane-Padgham, Beechie, & Klinger, 2017). In this context, the methodological approach adopted here identifies river systems where components that potentially buffer stream temperatures are absent or degraded.…”

“…It is widely accepted that climate change will have far reaching implications for freshwater systems and their biota (IPCC, 2014). Climate change may result in complex cause and effect sequences by modifying interacting river processes that are directly or indirectly influenced by temperature and precipitation (Donnelly et al, 2017;O'Briain, 2019). At the system level, the form and function of rivers is governed by hydrology, geology, vegetation, channel morphology and sediment supply (Poff & Ward, 1990;Poff & Zimmerman, 2010).…”