Revealing the true extent of lost salmon habitat in the Lower Fraser River

Nearly everyday, I walk by a monument memorializing Brewery Creek, a historical creek that meandered through the intersection of Kingsway and Broadway in the heart of Vancouver. Named for its utility in providing water to the breweries of the area throughout the late 19^th century, Brewery Creek was also home to multiple species of salmon. Today, nearly all of the streams within the city limits of Vancouver have met a similar fate to Brewery Creek – subject to rapid development, subsequent environmental degradation, and eventual conversion to underground drainage with no use to salmon, or breweries for that matter.

Freshwater habitats like Brewery Creek are critical for salmon to complete their life cycle. Cool streams are needed for spawning and the incubation of their eggs. For some species, including endangered populations of Chinook, juveniles rely on freshwater streams, side channels and floodplains for rearing habitat before they move to the ocean. The loss and alienation of freshwater spawning and rearing habitats lowers the capacity for our freshwater ecosystems to produce wild salmon that will eventually migrate to the ocean where they grow to the size that sustains our coastal ecosystems including endangered orcas and giant trees, our culture and economy, as well as underpinning food security for many First Nations in British Columbia.

Habitat loss

The process of habitat loss happens over time which can lead to a shift in perceptions of what is “normal” for the ecosystem at both an individual and generational level. Without the transfer of knowledge on the historical state of the ecosystem, the shifting perceptions of ecosystems can alter our behaviour in terms of how we manage the current landscape and interpret trends in populations. Without incorporating historical information into our decision making, we risk facilitating a managed decline in the state of the ecosystems and the species we value.

To document habitat loss and alienation within a historical context and resist the potential for a shifting baseline influencing how we perceive salmon habitat in the Lower Fraser, my co-authors from Raincoast, UBC and I gathered a number of datasets that describe the extent of salmon habitat connectivity and loss throughout the Lower Fraser River for 14 populations of salmon. This involved the integration of multiple sources of information describing current freshwater barriers such as dams, culverts, and flood infrastructure with models that predict the location and extent of lost streams, and historical floodplain vegetation from the late 1800’s.

Video about Riley’s research

Quantifying habitat loss

The resulting data identified over 1,200 in-stream barriers to fish passage. Across the region, we estimate that approximately 64% of formally accessible stream length either exists upstream of a mapped fish barrier or has been lost altogether, and approximately 85% of seasonal floodplain habitat has been made inaccessible by dikes. These estimates vary depending on the specific population that is considered, however, when we compared these accessibility estimates with the status of the population as assessed by the Committee on the Status of Endangered Wildlife in Canada, we found many of the most impacted populations remain unassessed. Particularly for species like Chinook and coho salmon, floodplain habitats offer access to improved growth rates through a wealth of terrestrial insects and protection from predators. Most of this seasonally available habitat is no longer accessible. 

Much like the memorial for Brewery Creek that reminds me that the neighbourhood I live in used to support thriving salmon streams, I hope this paper can act as a signpost for the history of the Lower Fraser River. By combining multiple datasets describing salmon habitat and the structures that limit access, we gain a new perspective on the scale of landscape change and the implications this has for salmon. Understanding the extent of habitat loss for salmon should raise our ambitions for freshwater habitat restoration, and influence any future development of the Lower Fraser and Estuary. Bringing this data together also lets us begin systematically planning and identifying priority projects for restoring thriving salmon streams throughout the Lower Fraser River. 

You can help

Raincoast’s in-house scientists, collaborating graduate students, postdoctoral fellows, and professors make us unique among conservation groups. We work with First Nations, academic institutions, government, and other NGOs to build support and inform decisions that protect aquatic and terrestrial ecosystems, and the wildlife that depend on them. We conduct ethically applied, process-oriented, and hypothesis-driven research that has immediate and relevant utility for conservation deliberations and the collective body of scientific knowledge.

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