Response to RC2

Abstract

Climate changes affect aquatic ecosystems by altering temperatures and precipitation patterns, and the rear edges of the distributions of cold-water species are especially sensitive to these effects. The main goal of this study was to predict in detail how changes in air temperature and precipitation will affect streamflow, the thermal habitat of a cold-water fish (the brown trout, Salmo trutta), and the synergistic relationships among these variables at the rear edge of the natural distribution of brown trout. Thirty-one sites in 14 mountain rivers and streams were studied in central Spain. Models of streamflow were built for several of these sites using M5 model trees, and a non-linear regression method was used to estimate stream temperatures. Nine global climate models simulations for Representative Concentration Pathways RCP4.5 and RCP8.5 scenarios were downscaled to the local level. Significant reductions in streamflow were predicted to occur in all of the basins (max. −49 %) by the year 2099, and seasonal differences were noted between the basins. The stream temperature models showed relationships between the model parameters, geology and hydrologic responses. Temperature was sensitive to streamflow in one set of streams, and summer reductions in streamflow contributed to additional stream temperature increases (max. 3.6 • C), although the sites that are most dependent on deep aquifers will likely resist warming to a greater degree. The predicted increases in water temperatures were as high as 4.0 • C. Temperature and streamflow changes will cause a shift in the rear edge of the distribution of this species. However, geology will affect the extent of this shift. Approaches like the one used herein have proven to be useful in planning the prevention and mitigation of the negative effects of climate change by differentiating areas based on the risk level and viability of fish populations.Published by Copernicus Publications on behalf of the European Geosciences Union.

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

“…The effect of hydromorphological alteration and extent of riparian cover on realised stream temperature is likely to vary across catchments and regions depending on the relative contribution of groundwater and other drivers such as micro‐climates to thermal regime. Various authors have reported stream temperature differences between rivers in the same local region underlain by contrasting bedrock types (e.g., Santiago et al, ) that were mediated by surface‐sub surface flow exchange. In this investigation, aquifer type or potential baseflow contribution did not strongly affect stream temperature regimes compared to other explanatory variables.…”

Extreme heat events and the vulnerability of endemic montane fishes to climate change

“…It is likely that this range of projections encompasses the true nature of T extreme event frequencies and magnitudes, but more multi-year paired air-water temperature time-series are necessary to reduce uncertainty in forecasts. Another consideration is that our projections of T extreme events do not explicitly incorporate the role of streamflow in mediating air-water temperature relationships which, in addition to temperature, is forecasted to change in southern Appalachia (Anandhi and Bentley 2018) and elsewhere in the world (Santiago et al 2017). For example, Merriam et al (2017) identified low flows in combination with high air temperatures contributing to thermal stress of Brook Trout in central Appalachian streams.…”

Stream channel restoration increases climate resiliency in a thermally vulnerable Appalachian river

“…network topology; Ebersole et al 2015), and regional-scale (e.g. precipitation; Merriam et al 2017;Santiago et al 2017) factors controlling thermal vulnerability to climate change. There is also a growing body of literature suggesting strategic conservation and restoration efforts, such as riparian restoration and structural enhancement or alteration (Hester et al 2009;Sawyer et al 2011;Justice et al 2017), can improve thermal suitability of degraded larger-river systems.…”