Trout populations face collapse in warming west, study warns
Story By Mark Hume with Photographs by Nick Didlick
For several years in British Columbia provincial fisheries experts and conservation groups have been taking steps to try and mitigate the impacts of climate change.
They have been building small impoundment dams at head-water lakes to hold back water for summer release, replanting stream banks to provide shade, and in one case, on Vancouver Island, convincing a regional authority to divert a portion of the domestic drinking water supply back into a stream.
All of this is aimed at keeping stream flows adequate for fish and providing cool water in an increasingly warm world.
Now a study by a team of 11 scientists from Trout Unlimited, the U.S. Forest Service Rocky Mountain Research Station and several other agencies has confirmed the importance and the urgency of this kind of work.
The research, published in August 2011 in the science journal, Proceedings of the National Academy of Sciences, warns that as the climate warms, suitable trout habitat in the West could be reduced by about 50 per cent over the next 70 years. With less water, and more shallow, warm sections in streams, native cutthroat populations could decline by as much as 58 per cent, brook trout could drop by 77 per cent, rainbow by 35 per cent and brown trout by 48 per cent.
Those are staggering numbers.
The exhaustive study which collected data from 10,000 sites focused on the western U.S., but its findings clearly holds a warning for all of North America.
Trout are cold water species and as the climate warms they will suffer wherever they are.
The study advances our understanding of climate change impacts by looking beyond temperature increases to the role of flooding and interactions between species, said Dr. Seth Wenger, of Trout Unlimited, the papers lead author.
He added that the impact of climate change can be blunted to a degree, and some of the trout population declines can be avoided, if existing habitat is protected and cold water drainages that have been damaged in the past are restored.
That is, of course, exactly the kind of work that Trout Unlimited and many other organizations are involved in, although many of them are struggling with small budgets and are faced with government intransigence.
On Vancouver Island, for example, fisheries biologists have been trying for years to get authorization to raise a weir at the outlet of Cowichan Lake, so that more water can be held back for summer release. Local authorities are blocking the move because lake shore owners are worried that they will lose some beach front.
And on the Salmon River, near Sayward on central Vancouver Island, local groups have been pushing for years to have a fish passage built around a BC Hydro diversion dam which blocks upstream migration. With a fish-way, salmon, steelhead, rainbow trout and char would gain access to the largely unused upper 40 kilometers of the river.
Mike Gage, a member of the Sayward Fish and Game Club and Chair of the Campbell River Salmon Foundation, has been pointing out for years in meetings that the upper Salmon watershed contains colder water and will be an important refuge for fish as the climate continues to warm. The proposal has been stuck at the committee stage for over four years and BC Hydro has told Mr. Gage that its not in the business of planning to mitigate for climate change. The Trout Unlimited study, however, makes it clear that everyone has to start taking the issue seriously and start working now to protect fish habitat . If we do not, there will be a catastrophic decline in trout (and by implication, salmon) populations throughout the West.
This report is a wake-up call, Chris Wood, the president and CEO of Trout Unlimited said in a release. The good news is that were already working to protect high-quality trout habitat, such as backcountry roadless areas on national forests. Were reconnecting tributaries to main stem rivers, and were restoring degraded habitat. It is imperative that we accelerate the scope and the pace of that work if we are to have healthy trout populations and the irreplaceable fishing opportunities they provide through this century.
The study, which was funded by the National Fish and Wildlife Foundation, the U.S. Geological Survey and the U.S. Forest Service Rocky Mountain Research Station, looked at a number of scenarios using different climate models. But even under the most optimistic model, cutthroat trout populations in the West faced a likely decline of 33 per cent.
This study validates the work TU is doing in the West and all across the country to protect, reconnect, restore, and sustain trout habitat, stated Mr. Wood. It also reinforces the danger in congressional proposals that would remove protection from backcountry roadless areas and cut funding for state and federal natural resource agencies.
In British Columbia, the study should raise alarms about any development proposals that would remove water from fish bearing streams, or that would result in habitat degradation. It should, for example, bring under intense scrutiny a proposal in the Okanagan that would see the Big White ski resort diverting water from the headwaters of the Kettle River, to service a growing number of condos and ski resort homes.
At the same time the study underscores the importance of work being done by people like James Craig, of the BC Conservation Foundation, who is working on the Thetis Lake, Craigflower Creek system, near Victoria, to ensure there are adequate summer flows for trout.
In a note, Mr. Craig says the ultimate goal of the project is to convince the Capital Regional District to amend its water storage license to require annual fish flow releases.
On the Charters River, Sooke River system, Mr. Craig has been working with the Capital Regional District to make sure that it keeps the need of fish in mind as it upgrades its water system.
The CRD’s recent replacement of the almost century old water supply pipeline, including the fish-friendly leaky parts, from Sooke Lake would have led to Charters River drying up in the summer time, writes Mr. Craig. Weve convinced CRD to permanently divert a portion of their domestic supply into the river at the anadromous barrier no small feat considering the importance of this supply and the immediate/long term costs for the District.
Work like that has been taking place in the background, largely ignored by the media, but the Trout Unlimited study makes it clear that such initiatives are vital if trout and salmon are to survive in our warming world.