Potential wood supply losses to spruce budworm in New Brunswick estimated using the Spruce Budworm Decision Support System

The Spruce Budworm Decision Support System (SBW DSS) was used to estimate potential volume losses to a future spruce budworm (Choristoneura fumiferana (Clem.)) outbreak in New Brunswick. The SBW DSS was implemented separately on each of the ten Crown Timber Licenses, using data from forest industry management plan timber yields and harvest schedules; values were then compiled for all of New Brunswick. Potential volume losses on privately owned forest (industrial freehold and private woodlots) were estimated by matching stand types with those for Crown land. Total potential volume losses of 83 million and 195 million m3 of spruce-fir (Picea spp. - Abies balsamea (L.) Mill.) were predicted for "normal" and "severe" budworm outbreak scenarios, defined based on past outbreaks in New Brunswick and Nova Scotia and assumed to start in 2000. Simulated timber supply losses were 42 million, 40 million, and 1 million m3 on Crown, freehold, and federal land, respectively, under a normal outbreak scenario, versus 99 million, 92 million, and 3 million m3 under a severe outbreak scenario. On Crown land, 33% of the predicted loss in a severe outbreak occurred in stands scheduled for harvest over the next 30 years, 26% occurred in stands not scheduled for harvest for at least 30 years, and 41% was in the non-timber harvesting landbase (11% in Old Softwood Forest Habitat, 12% in Deer Wintering Areas, 14% in riparian buffers, and 3% in inaccessible areas). Harvest levels 11-20 years in the future were very sensitive to reduction in yields caused by defoliation. Under a severe outbreak scenario, if 40% of the landbase was not protected for 2, 5, or 8 years to limit defoliation (simulating spraying the insecticide Bacillus thuringiensis, B.t.), 2007-2011 harvest level reductions of 4.0, 6.0, and 8.4 million m3, respectively, would be necessary. We conclude that the only way that planned harvest levels for New Brunswick can be maintained, under a future spruce budworm outbreak, is with effective targeted use of insecticides for forest protection.