Archive for August, 2013

Bog Blog – Denny Island celebrates International Bog Day on July 28th, 2013

Denny Island celebrated its first year of participation in International Bog Day, July 28th, with fun events highlighting the importance of this widespread ecosystem in the Great Bear Rainforest. International Bog Day is celebrated in various locations throughout the northern hemisphere on this day every year. The central and north coast regions have about as much wetland as they do closed-canopy forest, and most of that wetland is blanket bog complex, a mosaic of forested, shrubby, and open bog types. Here is some mind-boggling information about bogs.

What is a bog? A bog is a wetland dominated by plants, particularly Sphagnum mosses, which decompose very slowly and accumulate in the wetland. Bogs are also called mire, quagmire, and muskeg, and they can be found throughout the boreal ecosystems of the northern hemisphere as well as in some parts of the southern hemisphere. Bogs occur in cool, wet climates where the surface water is acidic and low in available nutrients, and where the rock substrate is also nutrient-poor. Low fertility and cool climate result in slow plant growth, but plant decay is even slower because the soil is saturated with water. There are two primary ways that a bog can develop: bogs can form as Sphagnum moss grows over a lake or pond and slowly fills it (terrestrialization), or bogs can form as sphagnum moss blankets dry land and prevents water from leaving the surface (paludification). Over hundreds or thousands of years, many feet of acidic peat (partially decayed plant) deposits build up in bogs of either origin.

The blanket bog-forest complex that we have in the coastal rainforest is a dynamic system where open bogs can develop into forests and vice versa, due to small changes in climate and water flow over long periods of time. Peatlands in this region are thought to have begun expanding into productive forests during a cooler and wetter period beginning 3500-6000 years ago.

The amount of bog on the outer coast is also a factor of infrequent disturbance (ie. from fire or flooding) and of bedrock geology; in most areas there is little to no glacial till, and soils develop directly from weathering of bedrock or eroded bedrock sediments. Bedrock types contrast sharply on the outer coast, from slow-weathering types with low nutrient elements, to much softer, fast-weathering types like limestone, which provide ample soil nutrients. Differences in topography (slope and drainage) and the underlying bedrock result in the different forest types that we see.

On Bog Day, a group of locals and visitors hiked into the upland bog to learn about the plants and animals that thrive there, and about the importance of bogs. Bogs are tremendous carbon sinks, they help to moderate climate, they store fresh water and prevent flooding, and they provide habitat to all kinds of species, like carnivorous plants and Sandhill cranes. Our destination was a Sandhill crane nest, already vacated by the birds, who seem to prefer the small islets of Sphagnum mosses and other plants in bog pools for their nest sites on this part of the coast. We spotted two cranes on our hike, and collected 4 moulted feathers to be used for DNA extraction in order to compare genetic markers of our small coastal population (approximately 4,200 cranes summering between the north end of Vancouver Island and SE Alaska) to those of inland cranes.

We are fortunate to have so many healthy wetlands in this region. In northern Europe, where they have been drained extensively for other land uses and peat extraction has occurred on a large scale, only 10% of bogs remain intact. A significant proportion of Canadian bogs have been altered for berry production or destroyed for horticultural peat extraction. On the B.C. coast, bog forests are considered ‘lower-productivity’ by the forest industry, but market demand for red and yellow cedar may eventually drive logging into the bog. Cleared bog forests may not regrow trees because of the increase in rainfall runoff, which raises the water table. Extensive research has already gone into making these ancient and slow-growing forests ‘operable’ for harvesting. Windfarms have been established on the blanket bog of northern Vancouver Island and on many bogs in northern Europe. They have been proposed for uninhabited, undeveloped outer coastal islands in B.C. such as Aristizabal and Price Islands and in Haida Gwaii. Road and platform construction associated with windfarms can alter bog hydrology, introduce exotic species, and change predator-prey dynamics resulting in long-term ecological damage.

Many thanks to all of the participants, including the prize-winning bog swimmers and hike co-coordinator Marlene Wagner, to Pacific Wild, Shearwater Marine Resort, and Rosie’s Boutique for hosting this event, and to TD Friends of the Environment Foundation for financial support.

Krista Roessingh

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