Lightning and Fires in the Northwest Territories and Responses to Future Climate Change

Lightning and fire characteristics within the Northwest Territories (NWT) jurisdiction of the Mackenzie Basin between 1994 and 1999 are examined using data from the lightning detection network operating in the NWT and from the national Large Fire Database maintained by the Canadian Forest Service. The convective storm season with associated lightning activity over this region is short but intense, with a strong peak in cloud-to-ground lightning during July. The maximum area of lightning activity is influenced by local moisture sources and by topography. The diurnal distribution of cloud-to-ground flashes indicates that most of the lightning was linked to thunderstorms initiated by daytime heating. The lightning-initiated fire occurrences peaked during July, while much of the burned area was produced in June. The longer, warmer, and drier summer seasons projected to result from climate change are expected to increase the frequency and intensity of forest fires by the end of the 21st century. Their considerable consequences for forests and wildlife make these changes a concern for northern communities, forest managers, and wildlife biologists.Les caractéristiques des éclairs et des incendies enregistrés dans le bassin du Mackenzie entre 1994 et 1999 sont examinées à la lumière de données obtenues à partir du réseau de détection des éclairs des Territoires du Nord-Ouest et de la Base de données sur les gros incendies du Service canadien des forêts. Dans cette région, la saison des orages de convection et les éclairs qui en découlent est courte, mais intense, les éclairs nuages-sol atteignant leur point le plus élevé en juillet. L’aire maximale visée par les éclairs est influencée par les sources d’humidité et la topographie locales. La répartition diurne d’éclairs nuages-sol indique que la plupart des éclairs provenaient des orages attribuables à la chaleur de la journée. Les incendies découlant d’éclairs ont atteint leur point culminant en juillet, tandis que la plupart des régions brûlées l’ont été en juin. Les étés plus longs, plus chauds et plus secs susceptibles de résulter des changements climatiques devraient augmenter la fréquence et l’intensité des feux de forêt d’ici la fin du XXIe siècle. Leurs répercussions considérables sur les forêts et sur la faune sont une source de préoccupation pour les collectivités du Nord, les experts forestiers et les biologistes de la faune

Lightning as a major driver of recent large fire years in North American boreal forests

Changes in climate and fire regimes are transforming the boreal forest, the world's largest biome. Boreal North America recently experienced two years with large burned area: 2014 in the Northwest Territories and 2015 in Alaska. Here we use climate, lightning, fire and vegetation data sets to assess the mechanisms contributing to large fire years. We find that lightning ignitions have increased since 1975, and that the 2014 and 2015 events coincided with a record number of lightning ignitions and exceptionally high levels of burning near the northern treeline. Lightning ignition explained more than 55% of the interannual variability in burned area, and was correlated with temperature and precipitation, which are projected to increase by mid-century. The analysis shows that lightning drives interannual and long-term ignition and burned area dynamics in boreal North America, and implies future ignition increases may increase carbon loss while accelerating the northward expansion of boreal forest