A scenario for impacts of water availability loss due to climate change on riverine fish extinction rates

Abstract

Summary1. Current models estimating impact of habitat loss on biodiversity in the face of global climate change usually project only percentages of species 'committed to extinction' on an uncertain timescale. Here, we show that this limitation can be overcome using an empirically derived 'background extinction rate-area' curve to estimate natural rates and project future rates of freshwater fish extinction following variations in river drainage area resulting from global climate change. 2. Based on future climatic projections, we quantify future active drainage basin area losses and combine them with the extinction rate-area curve to estimate the future change in extinction rate for each river basin. We then project the number of extinct species in each river basin using a global data base of freshwater fish species richness. 3. The median projected extinction rate owing to climate change conditions is c. 7% higher than the median background extinction rate. A closer look at the pattern reveals great geographical variations highlighting an amplification of aridity by 2090 and subsequent increase in extinction rates in presently semi-arid and Mediterranean regions. Among the 10% mostimpacted drainage basins, water availability loss will increase background extinction rates by 18Á2 times (median value). 4. Projected numbers of extinct species by 2090 show that only 20 river basins among the 1010 analysed would experience fish species extinctions attributable to water availability loss from climate change. Predicted numbers of extinct species for these rivers range from 1 to 5. 5. Synthesis and applications. Our results strongly contrast with previous alarming predictions of huge surface-dependent climate change-driven extinctions for riverine fishes and other taxonomic groups. Furthermore, based on well-documented fish extinctions from Central and North American drainages over the last century, we also show that recent extinction rates are, on average, 130 times greater than our projected extinction rates from climate change. This last result implies that current anthropogenic threats generate extinction rates in rivers far greater than the ones expected from future water availability loss. We thus argue that conservation actions should be preferentially focused on reducing the impacts of present-day anthropogenic drivers of riverine fish extinctions.

High Variability Is a Defining Component of Mediterranean-Climate Rivers and Their Biota

“…Predicted changes include increased variability in natural environmental conditions, with potential negative consequences for species persistence. A 2013 study at the global scale predicted a significant increase in extinction rates for fish with climate change [144], identifying small coastal basins located in the driest areas to be the ones that will experience the highest increase ( Figure 5). In the Mediterranean Basin, these correspond to coastal basins from the Region of Murcia in Southeastern Spain, the region of Attica in southern Greece, Cyprus, and most of northern Africa.…”

International Perspectives on the Effects of Climate Change on Inland Fisheries

“…Thus, temperature increases of only 1°C to 2°C are likely to affect swimming ability, growth rates, and reproduction, which in turn are likely to affect wild fish and aquaculture production. Fish species extinctions due to reduced water availability arising from climate change in arid and semiarid regions of northern Africa are very likely before the end of this century (Tedesco et al 2013).…”

“…For one of the most threatened species, Brown Trout Salmo trutta (Freyhof 2010), distribution forecasts for the Ebro, Elbe, and Danube river basins indicate that 64% of stream reaches will become unsuitable by the 2080s, with the highest risk of extirpation in the Elbe Basin (Filipe et al 2013b). The greatest changes in fish assemblages are expected for the southern regions by the 2050s and 2080s, whereas boreal assemblages will change less over the same periods (Tedesco et al 2013;Pletterbauer et al 2015).…”

“…Therefore, it is imperative that other anthropogenic pressures on inland fisheries (such as migration barriers, land use/abuse, fisheries overexploitation, excessive and poorly planned stocking of hatchery fish, alien species introductions, and physical and chemical habitat alteration), which are driven by continued human population and economic growth (Limburg et al 2011), be limited to the maximum degree possible. In fact, Tedesco et al (2013) reported that such pressures apparently explained more fish taxonomic biodiversity losses than did reduced habitat availability from climate change. Nonetheless, Xenopoulos et al (2005) predicted greater taxonomic biodiversity losses from climate change than from water withdrawal in many rivers.…”

“…However, most fisheries also face effects from the inherently global problem of climate change, which only can be understood and ultimately managed from a truly international perspective. The potential extent and range of such effects were illustrated by Xenopoulos et al (2005), who, assuming the A2 model for climate change, predicted a loss of 0% to 75% of the fish species in a variety of the world's river basins but with an uncertain time lag (Tedesco et al 2013). Here, we provide a range of perspectives from the International Fisheries Section of the American Fisheries Society on climate change effects on inland fisheries from standing and flowing waters in Africa, Asia, Australia, Europe, and Latin America.…”