Blog dedicated primarily to randomly selected news items; comments reflecting personal perceptions

Friday, December 19, 2014

Beaver Habitat

"It has long been known the release of methane from beaver ponds is more intense than for other types of wetlands. With the species' re-establishment and population growth in regions where beavers have been introduced, we set out to quantify whether the methane produced would be large enough to be significant."
"We found that valuable habitat area has been established by beavers over the last century. While this habitat contributes to the global methane gas emissions, the magnitude of this methane source is lower than many other natural sources and unlikely to be a dominant climate change driver."
"The growth of wetland habitats represents a re-naturalization of ecosystems to what they were in 1900."
Dr. Colin Whitefield, applied bio-geochemist
Intro to BWW

There was a time, decades ago when we would tie our canoe to the car roof and set off with our two boys for a day of canoeing in Gatineau Park, Quebec, just over the Ottawa River from the nation's capital. Paddling about Lac Philippe as we often did in the evening hours during a week day, and in the early afternoon hours on weekends we would often see beaver huts and around them as we sat in our canoes would come one those sharp slaps on the water as beaver warned others of our presence.

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Hiking into the interior of the park as we also often did we once came across a small lake that didn't amount to very much, on our way to climb a height we were familiar with. We stopped briefly at the sound of strange voices, then discovered those high-pitched sounds were that of beaver kits hauling themselves onto a log then flipping off from the log into the lake, having one whale of a time.

Hard by the street where we live in an outer suburb of the city, lies a ravined forested area, and through it runs a creek tending to become fairly low in the summer months, freezing over in the coldest winter months, and released to a roaring meltwater river in the spring. On occasion beaver find their way into the creek and they build a dam and a lodge for themselves, usually in quite out-of-the-way areas.

They munch down on poplars, their presence so close to human habitation a delight to some of the regular trail walkers in that woodland, but an offence in the eyes of others who complain to the municipality that they must be removed, and eventually they are captured and re-located and we miss them. Decades ago we used to see foxes roaming the woods, grouse and raccoons and the occasional skunk. Now, rarely.

Once, when spring floods quite inundated the creek the resident beavers, an adult and two cubs for some reason panicked as their lodge got swamped. Some of the nearby streets were flooded by heavy rains that added to the snowmelt and it turned out to be quite the environmental incident. All the more so when we saw the juvenile beavers waddling up driveways presumably looking for some kind of haven.

That's the human interaction story on a personal level, with beavers, those industrious, social animals whose architectural ability and aquatic homes are so fascinating. But this was a research project funded partially by a Natural Science & Engineering Research Council of Canada post-doctoral fellowship, published recently in the Royal Swedish Academy of Sciences journal AMBIO.

Algonquin Park, Sec Lake

The results of the research reported pond habitats and natural watercourses have been expanding, resulting from the global increase of beavers. The study covered the period from 1900 to the present, focusing on the effect of beaver population increase, relative habitat growth resulting in global methane gas emissions.

Beaver population increase since 1900 has resulted in about 42,000 square kilometres of new pond habitats in Eurasia and the Americas, along with over 200,000 kilometres of shore-line habitat. A hundred years on it was estimated that activities relating to beaver habitat had contributed up to 800 million kilograms of methane to the atmosphere annually, representing a 200-times growth from 1900.

From the 16th to the 19th Centuries the fate of beavers was a most unpleasant one. They were hunted to near extinction, thanks to the fur trade. Since then, however, laws regulating beaver harvesting through trapping, assisted species introduction into new environments and natural migration have led to a global population growth of about 30 million beavers.

The building of dams creates water-based eco-systems contributing to the development of methane-emitting ecosystems. In those ecosystems carbon-rich aquatic plant matter decompose on the pond bottoms where little oxygen exists, the end result being the release of methane into the atmosphere. It was found that methane emissions from wetlands account for less than 1% of total emissions released by fossil fuels combustion, by humans.

When we paddled about rivers and lakes as we did so often and manoeuvred into swampy areas, the rotten-eggs stench of swamp gas (methane) would greet our nostrils. And there is where we might see turtles, black water snakes, nesting waterbirds, wild rice growing, and cranberry bushes, and small carnivorous sundews among the rushes, sedges, horsetails and flowering plants crowding the narrow aisles of water permitting us entry to the swamps.

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