Roads to ruin: conservation threats to a sentinel species across an urban gradient

Abstract

Urbanization poses a global challenge to species conservation. This is primarily understood in terms of physical habitat loss, as agricultural and forested lands are replaced with urban infrastructure. However, aquatic habitats are also chemically degraded by urban development, often in the form of toxic stormwater runoff. Here we assess threats of urbanization to coho salmon throughout developed areas of the Puget Sound Basin in Washington, USA. Puget Sound coho are a sentinel species for freshwater communities and also a species of concern under the U.S. Endangered Species Act. Previous studies have demonstrated that stormwater runoff is unusually lethal to adult coho that return to spawn each year in urban watersheds. To further explore the relationship between land use and recurrent coho die‐offs, we measured mortality rates in field surveys of 51 spawning sites across an urban gradient. We then used spatial analyses to measure landscape attributes (land use and land cover, human population density, roadways, traffic intensity, etc.) and climatic variables (annual summer and fall precipitation) associated with each site. Structural equation modeling revealed a latent urbanization gradient that was associated with road density and traffic intensity, among other variables, and positively related to coho mortality. Across years within sites, mortality increased with summer and fall precipitation, but the effect of rainfall was strongest in the least developed areas and was essentially neutral in the most urbanized streams. We used the best‐supported structural equation model to generate a predictive mortality risk map for the entire Puget Sound Basin. This map indicates an ongoing and widespread loss of spawners across much of the Puget Sound population segment, particularly within the major regional north‐south corridor for transportation and development. Our findings identify current and future urbanization‐related threats to wild coho, and show where green infrastructure and similar clean water strategies could prove most useful for promoting species conservation and recovery.

Global Warming of Salmon and Trout Rivers in the Northwestern U.S.: Road to Ruin or Path Through Purgatory?

“…; Feist et al. ), and less‐favorable ocean conditions (Mantua ; Di Lorenzo and Mantua ) to negatively affect coldwater fishes. For some populations or fisheries that are heavily exposed and vulnerable, an additional 1–3°C of warming accompanied by those changes may well prove to be the road to ruin.…”

“…Although warming of the region's rivers is evident and temperatures during some months are now about 1°C warmer than 20-40 years ago, it is encouraging to note that salmon and trout populations remain widespread in the Northwest. Less encouraging is that the Earth is probably in the initial decades of a long-term warming period, and temperature increases will act synergistically with regional trends in hydrology (Luce and Holden 2009;Kormos et al 2016), nonnative species invasions (Sanderson et al 2009), human population growth and water use (Vörösmarty et al 2010;Feist et al 2017), and less-favorable ocean conditions (Mantua 2015;Di Lorenzo and Mantua 2016) to negatively affect coldwater fishes. For some populations or fisheries that are heavily exposed and vulnerable, an additional 1-3°C of warming accompanied 582 by those changes may well prove to be the road to ruin.…”

A Call for Collaboration among Water Quality and Fisheries Professionals

“…To date, most research has focused on physical impacts such as loss of pervious surfaces and changes in channel form that reduce sinuosity and floodplain access (e.g., Booth and Jackson 1997). However, pollutants in stormwater can result in diverse and significant impacts on fishes in receiving waters ranging from olfactory impairment (Sandahl et al 2007), and organ malformation (McCarthy et al 2008;McIntyre et al 2014) to mortality (Scholz et al 2011;Feist et al 2018). Although stormwater can be treated to reduce its impacts (Hsieh and Davis 2005), discharge volumes during storms are unpredictable and may exceed capacity of treatment facilities (Booth and Jackson 1997).…”

Fisheries Volume 45 Number 3 March 2020

“…To date, most research has focused on physical impacts such as loss of pervious surfaces and changes in channel form that reduce sinuosity and fl oodplain access (e.g., Booth and Jackson 1997 ). However, pollutants in stormwater can result in diverse and signifi cant impacts on fi shes in receiving waters ranging from olfactory impairment (Sandahl et al 2007 ), and organ malformation (McCarthy et al 2008 ;McIntyre et al 2014 ) to mortality (Scholz et al 2011 ;Feist et al 2018 ). Although stormwater can be treated to reduce its impacts (Hsieh and Davis 2005 ), discharge volumes during storms are unpredictable and may exceed capacity of treatment facilities (Booth and Jackson 1997 ).…”