Woodlands shaped by past Hurricanes
By David Dwyer, Forester
( photo NSNR&R 2003)
Many of our forest stands in Nova Scotia are a result of past hurricanes. Mounds on the forest floor -the result of uprooted trees - indicate this.
The age of trees growing on these mounds give a good indication of when the storm occurred. These stand ages compare well with the written records of past storms.
Just 25 years ago, on the night of September 11, 1954, Hurricane Edna hit Nova Scotia. As it moved into the Gulf of Lawrence the next morning, approximately 700 million board feet of lumber lay on the ground in the form of fallen trees. This was more than twice as much lumber as was cut in an average year in the 1950's.
This presented many problems to the lumberman of Nova Scotia. The blowndown trees had to be salvaged within a few years or they would be wasted. New roads had to be built. Salvaging operations would be expensive and selling the lumber presented problems.
Other hurricanes in past years had caused extensive blowdown. These trees, in most cases, had been left to rot.
Hurricanes, or tropical cyclones, originate in the tropics. They are storms of low atmospheric pressure with winds of over 120 kilometres per hour. These wind systems are inclined inward and are more or less symmetrical around the centre or "eye" of the storm. Commonly occurring in August, September, and October, they travel at various speeds averaging about 20 kilometres per hour. The hurricane may be compared to a child's toy which spins rapidly but changes its position slowly.
It can be said that hurricanes are Nature's way of thinning the forest. Patches of older trees are blown down, especially if they are exposed to southerly winds. In other areas only the weaker trees are removed from the forest stands.
Many factors determine what stands or trees are susceptible to blowdown. Excessive damage has occurred to forest stands on heights of land, south-facing windward slopes, margins of swamps and lakes, and along road-ways. Shallow soils over bedrock may also increase the amount of blowdown. The amount of moisture in the soil may also be a factor. Such factors as tree species, health, age, and past cutting all playa part in the amount of damage that will occur during a hurricane.
Many hurricanes have passed through Nova Scotia, but not all have caused forest blowdown. Many books, diaries, and reports have been SUI died. Forest stands have also been studied to determine if blowdown had ever occurred. Since many forest stands originated, liter the previous stand was blown down, the present forest age would indicate the storm 's date.
Early records are naturally sketchy and only those storms that seemed especially destructive in Nova Scotia are listed.
I. R. Tannehill, in his book Hurricanes, writes about the 1635 storm. On August 15 that year, he says, it caused "widespread destruction of trees" in New England. E. R. Snow, in The Vengeful Sea, confirms that on this date l major storm occurred. There are old growth stands in southwestern Nova Scotia, well over 300 years old, which may have originated from this storm.
E. R. Snow mentions the 1676 storm, a great hurricane which "... attracted considerable attention." Many of the old growth hemlock and red spruce stands are aged at about 300 years and possibly originated from this storm.
Titus Smith, Nova Scotia's first ecologist, reported in 1801 "that trees were all blown down here [an area in Queens County] by a hurricane about 80 years ago, which was followed by a fire next year, after which the young growth which now covers the ground, came up". This statement indicates that a hurricane occurred about 1721.
E. R. Snow states that New England experienced storms in 1717 and in 1723. Studies of forest ages indicated many old growth stands about 250 years old, which suggest both storms affected Nova Scotia's forests.
In 1798, on Sept. 25, The Great Storm hit the province. This is the earliest well documented storm to affect the forests of Nova Scotia. Titus Smith records in the report of his travels of 1801 and 1802 that in the area of Pollhook Lake, he was impeded by windfall, blown down in the great storm." He further noted in an area southwest of Windsor that he was"... obliged to spend a half hour in going 100 yards" because of the difficulty of traveling through forest blowdown
Titus Smith does not date the Great Storm he so frequently refers to, but Thomas Haliburton in his Historical and Statistical Account of Nova Scotia, Vol. 2, published by Joseph Howe in 1829, states that on September 25, 1798, there was "a dreadful storm and gale of wind at Halifax, by which shipping, wharves, and other property [was] destroyed, Most of the roads [were] rendered impassible from the falling of the forest trees across them,"
Forest stands over 170 years of age are sometimes encountered in Nova Scotia, and no doubt originated from the Great Storm.
The Long Island Hurricane struck the province in the first week of September, 1821. A common age of old growth forest stands in Nova Scotia is 150 years. It would seem reasonable to assume that this well known storm was the origin of many of these stands. Tannehill describes the path of this storm and records that while great damage occurred in New York, its force diminished as it approached the Maritimes.
Saxby's Gale is the memorable one predicted nearly a year before it occurred, on Oct. 3-5, 1869, by a Lieutenant Saxby of the British Navy. The gale rose to hurricane strength in the central Maritimes on the evening of October 4, and tides in the Bay of Fundy rose above any mark ever before recorded.
A common age of forest stands in Nova Scotia is 100 years. The origin of many of these stands is the blowdown resulting from Saxby's Gale.No doubt the Nova Scotia Storm of 1873 W.1S a contributing factor too. George MacLaren writes in his Pictou Book that the storm of August 24, 1873 "... was probably one of the most severe and destructive that has visited our coast in years". He calls it "The Big Blow."
Extremely high tides were reported at New Glasgow and Pictou. Vessels were driven ashore and many buildings were blown down MacLaren also reported that ". ..after this storm it was noticed that allover the country for miles inland the trees were wilted and turned brown. According to reports, this storm lasted 19 hours, dropped 4 inches of rain, and produced wind velocities up to 110 kilometres per hour.
Tannehill states that the U.S. Weather Bureau issued its first warning in connection with this Nova Scotia Storm of 1873. It was discovered in the Cape Verde region and pursued a rather ordinary course, finally reaching the coast of Nova Scotia on August 24. "It was very destructive there and in Newfoundland, New Brunswick, Labrador, and Prince Edward Island." It is recorded that more than twelve hundred vessels were lost in this storm.
There were many other storms reported during the period following the Nova Scotia Storm but none caused widespread damage to our forests until Hurricane Edna arrived on Sept. 11, 1954. Storms such as the Postland Gale of 1898, the Great Atlantic Hurricane of 1944, and Hurricane Carol of 1953 all caused damage; but none to such an extent as Hurricane Edna.
No doubt hurricanes will continue to play havoc with our forests. Forest managers must consider this problem when planning present cutting programs and future forests. This is important not only when evenaged management, or clearcutting, is being practiced, but also when unevenaged management, or partial cutting. is planned.