Citation | Hebda, R.J., K. Gustavson, K. Golinski and A.M. Calder, 2000. Burns Bog Ecosystem Review Synthesis Report for Burns Bog, Fraser River Delta, South-western British Columbia, Canada. Environmental Assessment Office, Victoria, BC. |
---|---|
Organization | Ministry of Environment |
URL | https://www.burnsbog.org/bog/wp-content/uploads/Burns-Bog-Ecosystem-Review.pdf |
Abstract/Description or Keywords | Burns Bog is a raised bog ecosystem covering approximately 3,000 ha of the Fraser River delta between the south arm of the Fraser River and Boundary Bay. On June 1, 1999, the Government of British Columbia and Delta Fraser Properties Partnership – the owners of 2,200 ha of land within the Bog - agreed to undertake an ecosystem review to gain a full understanding of what is needed to preserve the ecological integrity of Burns Bog. The purpose of the Burns Bog Ecosystem Review (the Review) was to determine the factors crucial to preserving Burns Bog as a viable ecosystem, such as the hydrology, geology, flora and fauna. The BC Environmental Assessment Office (EAO) was charged with managing the review process. The public and stakeholders contributed to developing the nature and scope of the studies undertaken. Gregory McDade, Q.C., Advisor to the Minister of Environment, Lands and Parks, facilitated public involvement throughout the review process. The public participated in reviewing study progress, and in Technical Review Meetings involving local, regional and international scientific experts. All project materials were accessible through the EAO Project Registry, at local information outlets, and over the Internet. The key Review findings and conclusions were developed from the results of technical studies, written submissions, Technical Review Meetings, and additional information and models developed by the EAO. The data and models available were generally adequate to lead to conclusions concerning the requirements for the ecological viability of Burns Bog. However, the data and analyses used in the Review were limited by the short duration of the study, a lack of previous investigations, and limited comparative data and examples. Burns Bog is globally unique on the basis of its chemistry, form, flora and large size. The Bog exhibits the typical characteristics of a raised bog ecosystem, including a peat mound above the regional water table, an internal water mound, acidic nutrient-poor water derived directly from precipitation, a two-layered peat deposit, and widespread peatland communities dominated by Sphagnum and members of the Heather family. Today, the Bog is largely isolated from other natural areas by agricultural, residential and industrial development. Forty percent of the original bog area has been alienated by development. Many activities, especially peat mining, have disturbed the hydrology and ecosystems of more than half of the remaining bog area and these disturbances continue to affect the Bog today. Despite these disturbances, Burns Bog retains important ecological processes and continues to support distinct biotic communities. The destruction of vegetation and the upper porous acrotelm layer, combined with the alteration of the hydrological and soil regimes, have impeded the peat-formation process. The Bog's hydrology is shaped by the water mound, fluctuating water levels in the acrotelm zone (top 50 cm), and an extensive system of ditches. The Bog’s ecological viability is directly dependent on the extent and integrity of the water mound and the peat that encloses it. The upper porous acrotelm layer is vital to the persistence of the water mound and peat-forming communities dominated by Sphagnum mosses. Only 29% of the Bog’s original acrotelm and its dynamic water storage zone remain intact. Water from the east side of Highway 91 may play an important role in sustaining shallow pools that support the main water mound. The acrotelm plays a vital role in regulating and storing water. As a result of increased rapid discharge through ditches, the average position of the water table in the acrotelm is about 25 cm lower than it was in the 1930s. Many ditches reach to the centre of the water mound from all directions and threaten the future of the Bog. None of the natural drainage channels and little of the essential lagg zone at the margins remain in the Bog. Further disruption of the water mound poses high risk to the viability of Burns Bog. The existing area of acrotelm must be maintained and a fully functional acrotelm must re-develop over the area of the water mound. A fully functioning lagg is required at the margins of the water mound. The lagg receives normal discharge from the bog and buffers bog water from adjacent mineral water. The overall loss of water storage and associated decline in the water table in the past few decades have contributed to the advance of forested vegetation adjacent to the lagg zone. The Bog’s water balance suggests a surplus of about 200 mm of precipitation over evapotranspiration for an average year. Monthly water balance analysis for an average year shows that there is a moisture deficit from April to September. The relatively low late summer water table, in the range of 27-39 cm below the surface, may explain why Burns Bog is located near the climatic limits for raised bogs on the west coast of North America. Typical bog water occurs in much of the main part of the Bog. It has low pH and relatively low calcium concentrations. A relatively narrow zone of transitional water, confined to the peat mass, separates bog water from surrounding mineral-rich waters. Non-bog water with moderate pH and relatively high mineral concentrations occurs outside the zone of transitional water and appears to be constrained outside the peat mass. Typical bog ecosystems are associated primarily with true bog water, and associated, in part, with transitional water. Originally, the Bog was covered in open heath and Sphagnum vegetation with scattered scrub pines. Today seven forest, nine shrubby and herbaceous, and six sparsely vegetated ecosystems occur. The unforested phases of the Lodgepole pine–Sphagnum ecosystem are likely responsible for most of the peat formation. Herbaceous ecosystems occur widely on abandoned peat workings and in some natural areas. Lodgepole pine and birch forests encircle the peat-forming central zone. Other forests, mostly dominated by western redcedar, occur mainly east of Highway 91. These forests include scattered old-growth trees and are considered to be regionally rare. Hardhack communities occur in the lagg zone at the Bog margins under influence of mineral-rich groundwater. The undisturbed peat-forming plant communities of the southern third and the north-west sector of the Bog are vital to its survival. Various plant species, including cloudberry, bog-rosemary, crowberry and velvet-leaf blueberry, occur at the limits of their geographic range and are recognized as genetically and ecologically important. The Bog also supports at least 12 species of Sphagnum, which constitutes 86% of the regional Sphagnum flora. The Burns Bog area includes several nationally and provincially listed animals in both the core central area and at the periphery. The Bog harbours the only known population of the red-listed Southern Red-backed Vole in the province, as well as the red-listed Pacific Water Shrew. It provides critical habitat for the regional Greater Sandhill Crane population. Rare dragonflies and water boatmen occur in the distinct wet habitats of the Bog. Areas at the Bog's periphery are especially important to rare species and wildlife diversity. The Bog plays an important regional role in ecological and wildlife diversity by providing habitat for Fraser River estuary waterfowl, and maintaining the largest extent of bog ecosystems in the Fraser Lowland. The Bog area is highly sensitive to fire because only about 540 ha of fully functional peatforming vegetation may survive the next 100 years under the current fire regime. The Bog is also at risk to a series of drought years that could markedly lower the position of the late summer water table and threaten typical bog communities. The Bog area must remain large to withstand these disturbances. Connectivity is limited, but is required to maintain wildlife corridors and the long-term viability of the Bog. The conditions for recovery of Burns Bog ecosystems are favourable because there are many patches of bog vegetation in the disturbed area and a large natural zone surrounding the disturbed core. Widespread Sphagnum regeneration is occurring in the abandoned peat workings of the central bog. To ensure the Bog’s ecological integrity and viability, the entire extant water mound and most of the lagg zone are required. This requirement includes all of the west and central portions of the Bog. The area east of Highway 91 and north of 72nd Avenue is required to support high biodiversity attributes, to provide water to the main part of the Bog west of Highway 91, and to connect the Bog to upland habitats. The main water mound zone needs to be connected to the area east of Highway 91 via a broad zone of Sphagnum regeneration and typical bog water. Water in the shallow ponds within this zone supports the water mound. To sustain the water mound and peat-forming vegetation, ditches that drain the core of the Bog must be blocked as soon as possible or the Bog will not survive. In summary, the area required to preserve Burns Bog as a viable ecosystem includes about 2,450 ha of the remaining bog. Approximately 360 ha, mostly in the south-east and north-east portions of the study area, have significant values that support the Bog, but that are not required to ensure ecological viability. Only 14 ha are of low or no value to ecological integrity. Further studies of hydrology and wildlife are required to define the ecological configuration of specific sites at the margins of the area required for viability. A program of ongoing monitoring of key indicators of ecological integrity should be established to ensure the viability of this globally unique ecosystem. |
Information Type | report |
Regional Watershed | Lower Fraser |
Sub-watershed if known | |
Aquifer # | |
Comments | |
Project status | complete |
Contact Name | Richard Hebda |
Contact Email | [email protected] |