Field of Science

CSWA field trips: 2. Banff

On Monday attendees at the Canadian Science Writers' Association meeting went on a field trip to Banff.  We didn't see the city at all - we went straight from its new recreation centre out into the field with park naturalists, learning about four different aspects of the park.  First was fire, then traditional human use of the land.  The last two were the most interesting - different aspects of how roads and railways affect the movement of park animals, first land mammals and then fish.

How do park animals cross the road?  The park is traversed east-west by the Trans-Canada Highway, and most interactions between animals and humans used occur along the road.  Humans have traditionally been thrilled to see animals by the roadside, but the animals haven't fared so well, with many being killed by cars and trucks.  Part of the highway (~45 km) has been recently widened ('twinned', with separated eastbound and westbound lanes), and one goal of the improvement project was to reduce harm to the animals.  One component is 2.4 m high fencing all along the improved highway,  with a 1.5 m 'apron' under the ground to block burrowing.  Complementing the fencing are tunnels and overpasses that allow animals to safely cross.  As VIP visitors (lucky us) we were taken up onto a 50 m wide wildlife overpass that allows large animals (bears, lynx, elk etc) to cross the highway while feeling like they're still in the park.  Park staff limit visits to the overpasses to only a few times each year, so that human scent won't alarm the animals - we were joined by visiting staff from the national park system of China, looking for ways to manage their wildlife.  The sides of the overpass are 'bermed', with earth banked up so you can't see or hear the traffic, and there are infrared-triggered cameras that capture snapshots of passers-by.

Now that the bears can safely cross the road, another hazard has moved to high priority - being hit by a train.  Bears like to walk along railroad tracks, but they don't realize that they should get out of the way of approaching trains, and the trains can't stop in time.  This problem hasn't been solved yet.

What about the fish?  Fish?  Why would fish need to cross the road?  The main river through the park runs parallel to the highway, and many side streams join it through culverts (pipes under the highway).  Fish need to be able to move back and forth between the streams and the river, but the culverts often block this.  When the stream's flow rate is high, the water moves even faster through the narrow culvert (the aquatics expert said this was the Venturi effect, but that's not what Wikipedia says...).  The fish may not be able to swim upstream against this current, especially because a culvert doesn't provide them with anywhere to rest.  So culverts are being replaced with much wider culverts or mini-bridges, and their bottoms are being filled with the same diverse materials found in natural stream beds.

A fast-flowing culvert will wash away the soil and gravel at its outflow point, creating a mini-waterfall.  But unlike salmon, most fish can't jump, so they can't get into the culvert from its downstream side.  Parks staff are redesigning the culvert outflows to eliminate this problem.

Next: the field trip to the Athabaska oil sands...

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