Bidirectional connectivity in rivers and implications for watershed stability and management

Abstract

River networks are connected in both upstream and downstream directions on large spatial scales by movement of water, materials, and animals. Here I examine the implications of these linkages for the stability, productivity, and management of watersheds and their migratory fishes. I use simple simulations of watershed alteration to illustrate that degradation can erode the productivity and stability of both upstream and downstream fisheries. Through analysis of an existing global dataset on rivers, I found that larger rivers tend to be more fragmented than smaller rivers. I offer three challenges and opportunities for the future management of watersheds. First, given that human impacts can spread up and down rivers, there is a need to align the scales of impact assessments with the natural scale of river systems. Second, free-flowing rivers naturally dampen variability; thus, the conservation of connectivity, habitat, and biodiversity represents a key opportunity to sustain the processes that confer stability. Third, watersheds represent natural units of social-ecological systems; watershed governance would facilitate reciprocal feedbacks between people and ecosystems and enable more social-ecological resilience.Résumé : Les réseaux hydrographiques sont connectés tant vers l'amont que vers l'aval à de grandes échelles spatiales par le déplacement de l'eau, de matières et d'animaux. J'examine les conséquences de ces liens sur la stabilité, la productivité et la gestion des bassins versants et de leurs poissons migrateurs. J'emploie des simulations simples de l'altération des bassins versants pour illustrer le fait que la dégradation peut éroder la productivité et la stabilité des ressources halieutiques tant vers l'amont que vers l'aval. En analysant un ensemble existant de données planétaires sur les rivières, j'ai constaté que les grandes rivières ont tendance à être plus fragmentées que les rivières plus petites. Je propose trois défis et occasions à saisir pour la gestion future des bassins versants. D'abord, étant donné que les impacts humains peuvent se propager vers l'amont et l'aval des rivières, il est nécessaire que l'échelle d'évaluation des impacts coïncide avec l'échelle naturelle du réseau hydrographique. Deuxièmement, les rivières au libre cours atténuent naturellement la variabilité, de sorte que la conservation de la connectivité, des habitats et de la biodiversité représente une occasion clé pour soutenir des processus qui confèrent de la stabilité. Troisième-ment, les bassins versants constituent des unités naturelles de systèmes socioécologiques; la gouvernance des bassins versants faciliterait des rétroactions réciproques entre les humains et les écosystèmes et permettrait une plus grande résilience socioécologique. [Traduit par la Rédaction]

Borders and Barriers: challenges of Fisheries Management and Conservation in Open Systems

“…Recent evaluations of large rivers and their biota have called for adapting management methods that account for the breadth of ecological boundaries (i.e. watersheds; Pracheil et al , Koehn, , Moore , Pope et al, ). However, this study highlights the inconsistency between the scales at which fisheries management is currently conducted and the scale of river systems because ecological boundaries rarely align with human‐defined jurisdictions.…”

Spatiotemporal patterns of mountain whitefish (Prosopium williamsoni) in response to a restoration of longitudinal connectivity

“…Our results, in conjunction with other studies (Baxter, 2002;Benjamin et al, 2014;Radinger & Wolter, 2014), highlight the importance of longitudinal connectivity for mobile nondiadromous fish by allowing them to migrate for purposes other than reproduction. sediment flux), when assessing the effects of natural and artificial obstructions on the longitudinal connectivity of river ecosystems (Calles & Greenberg, 2009;van Leeuwen, Dokk, Haugen, Kiffney, & Museth, 2017;Moore, 2015). sediment flux), when assessing the effects of natural and artificial obstructions on the longitudinal connectivity of river ecosystems (Calles & Greenberg, 2009;van Leeuwen, Dokk, Haugen, Kiffney, & Museth, 2017;Moore, 2015).…”

Whole‐system perspectives in rivers: Insights and implications

“…There is emerging scientific appreciation that consideration of rivers as whole systems can provide insights into their dynamics and functions (McCluney et al ; Moore ; Moore et al ). Rivers represent vast tree‐like networks of connections.…”

“…The connectivity of rivers can make them more sensitive to the cumulative impacts of multiple development projects (McCluney et al ; Moore ). Land‐use changes are propagated downstream and upstream through vast river networks.…”

“…Recently, we discovered that larger catchments which integrate more diversity, have greater stability (less variability) in water flows, water temperatures, and First Nations salmon fisheries catches (Moore et al ). However, loss of local diversity within river networks could compromise the stability of the whole (Moore ).…”