Reply-A re-examination of the effects of fire suppression in the boreal forest

Ward and Tithecott (P.C. Ward and A.G. Tithecott. 1993. Ontario Ministry of Natural Resources, Aviation, Flood and Fire Management Branch, Publ. 305) presented data that indicated fire suppression activities in Ontario led to reductions in average annual area burned and greater numbers of small fires, compared with what would have been observed in the absence of suppression. Miyanishi and Johnson (K. Miyanishi and E.A. Johnson. 2001. Can. J. For. Res. 31: 1462-1466) have questioned aspects of that report, suggesting that the evidence does not demonstrate that suppression influences fire size or frequency. Fire-history studies in Ontarioʹs forests and recent fire disturbance records do show that the fire-return interval has lengthened considerably in Ontarioʹs protected forest since pre-suppression times. Analysis of forest inventory age-class distributions also reflect a reduction in overall forest disturbance rates in the past 40 years. Average annual burn fractions (ABF) calculated for protected and unprotected forests in northwestern Ontario for the period 1976-2000 show an ABF of 1.11% in the unprotected forest and only 0.34% in the protected forest. There is clear evidence that fire suppression in Ontario contains many fires at small sizes that would have otherwise grown to larger sizes, and reduces the overall average annual area burned in the protected forest.