Mapping Natural Phenomena: Boreal Forest Fires with Non-discrete Boundaries

Abstract

Forest fires are spatially and temporally frequent in the boreal forest biome and continue to alter the spatial mosaic of its forest cover. Some of these fires occur in remote locations where direct socio-economic impacts are negligible, and are therefore not suppressed. However, these natural fires have many ecological consequences, and their monitoring and mapping therefore pose both an important and a challenging task. The current state of the art for fire-event mapping in remote northern Ontario is conducted at variable cartographic scales and generally relies on recording the approximate perimeters of the burned area from fixed-wing aircraft or helicopters with a handheld global positioning system receiver. All such techniques treat forest-fire boundaries, regardless of their detection and mapping resolutions or of the irregularity and gradient-like characteristics of their burned/not-burned interface, as crisp lines. Here we describe a procedure for standardizing the mapping of forest fires by an approach using high-spatial-resolution IKONOS satellite imagery that considers the actuality of gradual boundaries by assessing the fire-membership strength of each pixel prior to developing a footprint describing an individual fire event. Our case study is from northern Ontario, Canada, where the remote boreal forest fires are not regularly suppressed or monitored/mapped using traditional means. Furthermore, our analysis explores the sensitivity of this mapping effort to spatial resolution when describing measures of fire-footprint spatial geometry. We compare our mapping results with fire boundaries obtained by other means, using a series of overlap statistics to assess their spatial coincidence.