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Downed wood and snags both are sources of forage, nests, and shelter for wildlife. Large trees and snags are critical for some species such as pileated woodpeckers and barred owls, which do not use cavities in trees smaller than 50 cm in diameter at breast height (see Bunnell and Dupuis 1994). Tree patches serve as perches, nest sites, contribute organic detritus to the food web, provide cover and travel ways for all wildlife. Large (continuous) patches of healthy and moribund trees also provide a sustainable recruitment of snags and downed wood for future wildlife use. Standing and downed wood in the intertidal zone is equally valuable, as it increases the availability of substrates for bottom-dwelling algae and invertebrates to dwell in.
Other important habitat attributes include rock outcrops, talus fields, and fresh water wetlands. Rock outcrops provide sunning, denning and roosting opportunities for birds and mammals, particularly bats, whereas talus slopes provide cool, moist refugia and wetlands host amphibians and freshwater fish.
1.3 Vulnerable and Keystone Species
The ecology of most species is unknown and therefore it is important to consider the requirements of a subset of focal species when situating and designing a protected area for the conservation of local biodiversity. Focal species include keystone species, vulnerable species and communities, and umbrella species whose needs encompass the needs of smaller-ranging species. Salmonids are keystone species in the Squamish estuary. They are a major contributor of nutrients to the local rivers and their riparian borders, and they govern the distribution and abundance of many consumers in the temperate coastal forest. Salmon migration through the estuary is responsible for the large, internationally recognized concentration of overwintering bald eagles in the lower Squamish watershed. Eelgrass is a keystone species in many estuaries. Eelgrass beds provide shelter for hundreds of species of small animals, and spawning habitat for schooling fish and shellfish. The blades of grass provide food for waterfowl and invertebrates. The dead leaves are an important contribution to the detritive food web. Eelgrass plants absorb and process nutrients and pollutants; their roots stabilize shallow marine sediments (www.wa.gov/Publications/pshealth2002/habitat_eelgrass.htm). Edith Tobe has begun a program to introduce eelgrass beds along the edges of Central Channel.
On a more local scale, pileated woodpeckers are a keystone species because they provide cavities for use by raptors, wood ducks, and mid-sized mammals. The northern flicker, hairy and downy woodpeckers create cavities for smaller secondary cavity nesting birds and mammals. Crescent Slough and Site A contain all five local species of woodpeckers and undoubtedly contribute to the high levels of wildlife biodiversity in the estuary’s riparian zone and adjacent floodplain forest. There are no known rare or endangered plant communities or species in the Squamish estuary, but birds of concern do migrate through the estuary during the spring and fall. For example, the northern goshawk and barn owl have been sighted in Site A in recent years, and small numbers of western grebes pass through the outer estuary annually. Steelhead populations have declined in response to human-induced habitat alterations; this species is present in the estuary year-round, and is making use of the newly built spawning and rearing channels.
2.0 Protection Priorities
The Squamish Estuary is a large wetland draining a 2330 km2 valley. It contains relatively large, contiguous stretches of salt marshes and bordering floodplain forest. Its habitat mosaic represents a highly complex structural environment that supports at least 260 species of fish and wildlife. Because of its size and high biodiversity level, the Squamish estuary contributes significantly to regional biodiversity levels and as such, merits much conservation consideration.
To maintain the integrity of an ecosystem, it is essential to understand the key habitat and landscape parameters that maintain its spatial, functional and compositional elements. Key elements of the Squamish estuary include the relatively undisturbed brackish tidal channels (Central Channel), productive saltmarsh zones (East Marsh, Bridge Pond), areas with high levels of structural diversity (several habitat types and inherent edges; Bridge Pond and Crescent Slough), rearing and spawning channels (North Field and East of Fill), and mature forest (Site A and Crescent Slough). To preserve the biodiversity “hot spots” that these key features support, it is essential to (1) create a natural protected area (reserve) that is large enough to contain functional and self-sustaining habitats even if the reserve becomes isolated in time, and (2) safeguard the integrity of core areas by managing the surrounding land matrix from an ecological perspective.
The soon to be designated provincial Wildlife Management Area (WMA) largely meets the first goal, by setting aside the bulk of the salt marshes and tidal channels with fish and wildlife needs in mind. Within the WMA, protection priorities should be geared toward the prohibition of motorized vehicles, and the establishment of trail networks that are strategically placed to minimize the displacement of staging water birds because long-distance migrants are usually tired, hungry and vulnerable. Pedestrians should also be efficiently directed in and out of prime wildlife breeding areas (e.g., riparian zones) within and beyond the WMA. Protection of the Squamish estuary’s integrity must be primarily focused on buffering “hot spots” (habitat and landscape features that support high species richness) from adjacent land uses. Specific protection priorities are listed below, in order of importance:
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Bridge Pond has the highest level of avian biodiversity in the estuary (BSC data). The richness of wildlife in Bridge Pond is attributed to this site’s high number of ecotones. Despite its small size, Bridge Pond has six habitat types, and these are intersected by a brackish slough and a large, partially dendritic tidal drainage system. Productivity is high in Bridge Pond likely because of the periodic release of storm water from the municipality’s downtown area retention pond (former sewage lagoon) known as “stinky lagoon”. Bridge Pond is the most threatened part of the estuary because it is slated for commercial/industrial development. Wildlife would be permanently displaced, including an average of 900 bird visitors per year, representing up to 127 different species.
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Developing Bridge Pond would also remove the forest buffer that is currently protecting the WMA from the town centre. Urban, agricultural or industrial centres can deteriorate unbuffered reserves, particularly wetlands, in a number of ways such as introducing toxins through storm run-off from hard surfaces, changing ecosystem functions by introducing exotic species or improperly treated sewage, land filling, introducing noise pollution and not managing activities in important wildlife areas. Despite the enormous value of riparian zones to fish and wildlife at the habitat and landscape level, riparian ecosystems when compared to upland habitats may total up to 0.5% of the landscape in western North America (Cooperrider et al. 1986), and roughly 75% of natural riparian ecosystems in British Columbia have been altered or lost to human activities (Bunnell and Dupuis 1994). The value of streamside habitats, their scant representation in the landscape, and the high level of threat they are exposed to in urban, commercial and industrial centres, make riparian zones a very important conservation attribute. The buffer along the undeveloped portion of the estuary is currently intact all the way up to Crescent Slough, and continuous tree buffers are far more effective at offering visual separation, reducing noise, filtering surface run-off and all its toxins, moderating floods and stabilizing the banks of watercourses. It is in the estuary’s best interest to ensure that this continuous riparian buffer be maintained.
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The commercial/industrial transportation corridor being proposed along the rail line to the Terminals will also remove forest buffers along the main saltmarshes of East Delta (East Marsh, North Field), remove some of the mature floodplain forest of Site A, and impinge on Crescent Slough (Squamish Estuary Coordinating Committee 1999). Crescent Slough has the third highest level of biodiversity, and the third highest bird biomass in the estuary because of its complexity of habitats and channels. Site A and Crescent Slough house pileated woodpeckers, which need large snags, large tracts of contiguous forest, and access to riparian habitats for survival. Pileated woodpeckers are a keystone species in the estuary woods and protecting its habitat requirements will benefit smaller ranging wildlife as well as larger species that breed in big tree and snag cavities (e.g., owls). A road into the bend of Crescent Slough may displace many species including the pileated woodpeckers, large cavity nesters, and possibly overwintering trumpeter swans, by introducing high noise levels. Road construction and traffic also increase the input of pollutants from fuel and oil spills.
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The proposed commercial/industrial road’s destination at the southwest corner of the Terminals, and the fact that the commercial/ industrial zone extends roughly 20 metres into Central Channel implies a possible intention in the future, of having freight traffic into Central Channel. Motorized boat traffic would reduce the quality of the estuary a number of ways: (1) engine leaks would decrease water quality, (2) boats wakes (especially jet boats) would cause erosion of the mudflats, saltmarshes and channel banks; (3) the noise and presence of boats would deter migrating and wintering birds from Central Channel and the Outer Estuary. In summary, extending the commercial/ industrial zone into Central Channel would counter and possibly negate much of the public, municipal and provincial effort to protect the estuary as a wildlife management area. Motorized boat activity should be prohibited in Central Channel. It should also be prohibited in Squamish River because of its link to Central Channel, its proximity to the pristine western delta, and its negative influence on water quality; the Squamish River is home to an important group of keystone species for this area (salmonids).
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Undisturbed land adjacent to the intertidal zone is rare (BC Nearshore Habitat Loss Work Group 2001). Any mature or old-growth forest in the Squamish Estuary is thus of regional significance and should receive high protection priority. Site A and Crescent Slough not only contains mature forest, they represent a major wildlife passage into the central and eastern parts of the undeveloped estuary. Limited hiking trails are unlikely to displace wildlife, but development of roads (e.g., proposed transportation corridor) and buildings (e.g., potential interpretive/cultural centre) in these mature woods would cause habitat fragmentation and the loss of forest interior conditions.
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Although a proportion of the Squamish Estuary is protected within the soon to be designated provincial Wildlife Management Area (WMA), weary migrants and overwintering water birds in Central Channel (including Crescent Slough), the Central Delta (including East of Fill, Training Dyke, Squamish River and West Delta), and parts of the East Delta (most of East Marsh, North Field and Site A) can be protected from direct disturbance by hikers, kite board and windsurfers, and non-motorized watercraft users by planning a strategic trail network with few access points to the water line, and specific windows of opportunity for recreation (see Management Recommendations). Access to Central Channel and its shores should be limited. The channel itself hosts the largest biomass of overwintering and migrating diving ducks, and its edges (East Marsh, North Field, and East of Fill) accommodate the majority of dabbling ducks. East Marsh is particularly critical because the Squamish and Mamquam Rivers least influence it, and its level of salinity is conducive to very high concentrations of algae in the bottom sediments and water column. Nearly three quarters of all shorebird visitors have East Marsh as their destination. East Marsh has the second highest biodiversity of birds in the estuary, after Bridge Pond. East of Fill and North Field are crucial to the survival of salmonid populations; the Department of Fisheries and Oceans has invested much time and money into the construction of spawning and rearing channels in these locations.
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Mamquam Channel has the second largest bird abundance in the estuary’s foreshore, particularly in early winter and late spring. Mamquam Channel is at higher risk from industrial and commercial activities, as a result of log handling facilities, a sawmill and the contaminated Nexen site. Conservation and management options are more limited here. Some recommendations are made in Section 7.0, to minimize disturbance as much as possible. The head of the blind channel is rich in structural diversity (exposed rock outcrops, deep sheltered rock crevices, freshwater wetland, tidally influenced shoreline). Consequently it has a rich diversity and abundance of birds, reptiles, mammals and amphibians. Of particular interest are: (1) the largest heron rookery in the estuary, across from the government wharf; (2) concentrations of herring roe on the sawmill pilings and in the marinas during spawning season; (3) Rose Park, which is an important migratory stopping point for many passerines; and (4) the isolated marsh, which is teaming with wildlife and a significant foraging ground for the peregrine falcons nesting overhead. The special features and high levels of biodiversity of the Upper Mamquam Blind Channel should be taken into account during the Planning Assessment for this area, under the Squamish Estuary Management Plan (SEMP). For example, a boardwalk along part of the blind channel waterfront may have conservation value for spawning herring and salmon smolts seeking cover. Conversely, the filling of the isolated marsh would displace many species, including 85 birds species.
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