Spruce/Fir Inventory and the Spruce Budworm

By Ken Laustsen, former biometrcian, Maine Forest Service

Within the last 100 years, Maine has experienced two major spruce budworm outbreaks (circa 1910 – 1920 and circa 1972 – 1985).  The most recent outbreak was severe enough to require a massive spray program and accelerated harvesting in attempts to mitigate inventory losses due to mortality.

An apparent peak, the 1970 statewide inventory estimated 127 million spruce/fir cords of pulpwood quality.  By 1981, the inventory had declined 9% to 115 million cords.  This data from Maine’s 1981 periodic inventory was used in various modeling projections and the bulk of those indicated that a continuing epidemic and harvest levels would totally deplete the spruce/fir resource by the year 2020.

The next available inventory in 1986, was a state-led effort to again get an estimate of inventory levels, right after the circa 1985 collapse of the outbreak.  This estimate of 91 million cords was a 21 percent decrease in just five years from 1981.  Inventories continued to decline mostly due to harvesting, bottoming out in 2008 and 2010 at 71 million cords of spruce/fir inventory.

Putting this into context with the previous epidemic, in 2008, 25 years after the start of the circa 1973 epidemic the spruce/fir inventory was 87 percent higher than a similar point in 1944, which had an inventory estimate of 38 million cords, which was 25 years after the circa 1919 outbreak.  The spray program, targeted harvesting, pulp mill conversion to hardwoods, and professional forest management; all helped to alleviate the dire projections of the early 1980s.