Forest Preservation

"These trees [surviving wildfires] are lifeboats. There are some places in the landscape that seem to avoid fire time and time again."
"[A strategy for preserving refugia evades ecologists as yet]. That requires identifying where they are and why we think they're important."
"[If researchers can agree, an atlas of fire refugia could result]. That would be sort of the Holy Grail."
Meg Krawchuk, Oregon State University

What are fire refugia?: Wildfires are familiar landscape disturbances in forested ecosystems of western Canada and the United States that result in mosaics of fire effects. The concept of burn severity is used to quantify biological, physical, and chemical effects of fire, and can be broadly defined as the degree to which an ecosystem changes as a result of fire. Landscape heterogeneity produced by burning, which can include a range in severity from unburned patches to high severity fire, is important to conserving characteristic biodiversity of fire-adapted ecosystems. As a part of the burn mosaic, areas that experience comparatively low-severity fire or remain unburned are landscape legacies that can provide an essential environment for species sensitive to fire, and support populations that contribute to the reassembly of biotic communities after fire. Fire islands, residuals, remnants, skips, shadows, refuges, refugia, or unburned patches are all terms used to describe areas at the low end of the burn severity spectrum. Here, we use the term fire refugia to describe places that are disturbed less frequently or less severely by wildfire than the surrounding landscape matrix. Refugia can exist at a range of spatial scales, e.g., from an individual plant or small patch of vegetation to broader landscapes. And refugia can occur across a range of temporal scales, persisting only in the short term through a single fire event or in the longer-term through multiple events. The term fire refugia is adapted from the broader concept of refugia as places providing environmental stability and facilitating species persistence as regional biotic and abiotic environments change. An understanding of the processes and patterns of fire refugia formation, maintenance, and ecosystem role across multiple spatial and temporal scales is critical as we (society) strive(s) to meet landscape fire management and ecosystem restoration goals, now and into the future.
Landscape Fire and Conservation Research Group, Oregon State University

Firefighters try to stop a wildfire as wind drives embers across Highway 20 near Clearlake Oaks, Calif., on Sunday, July 1, 2018. (AP Photo/Noah Berger)

"We might have a change of wind, it cools down at night, and the fire might not grab that patch of forest."
Arjan Meddens, University of Idaho

Trees and plants manage to survive even while forest fires rage within their range, in small isolated areas that ecologists have named 'refugia'. They are discrete refuges where green still meets the eye despite that they're an oasis in the midst of a grey, ashen, smouldering forest. They are areas where the fire for one reason or another has somehow skipped over, left intact to flourish and to succour whatever wildlife may have found its way within its haven, and will in time spread to bring new life to the burnt-out forest.

Those islands of green grass, shrubs and trees within the larger landscape of barren disaster are fire refugia, vital long-term to forest regeneration. They are where species can shelter. And they become the starting gate for the ecosystem's race to restore itself. Refugia are not yet full understood by botanists and ecologists but those involved in the well-being of forests understand full well that reaching a fuller understanding of how and why they survive can be critical to their ongoing capacity to save forests.

Climate change may threaten both the refugia existence and their valued capacity for restoration of the forest ecology. Fire refugia have been referred to by ecologists over the years as fire shadows, unburned islands, skips, or stringers in recognition of their function. While a forest fire rages desperate animals seek out shelter within refugia. And from their refuge there as the forest gradually regenerates those animals are able to return to refugia for nesting and to seek out food.



The charred landscape eventually welcomes seeds of trees that have survived within a refugium and new plants are slowly produced. Researchers relying on a half-century of satellite data are slowly piecing together those sanctuaries' histories. In the wake of a fire, refugia represent and resemble a glowing green gem in their scattering across blackened landscapes. Because of this phenomena, up to 25 percent of a forest is enabled to survive.

The north sides of mountains favour refugia in the Northern Hemisphere where plants are exposed to less sunlight enabling them to hold more moisture in their trunks and roots, as a consequence. Biodiversity is hugely dependent on these shelters. Patches of grasslands that catch fire yearly may survive one year and burn the following year. Yet these uneven fire refugia are invaluable to their survival as opposed to grasslands that burn in their entirety yearly, threatening the butterflies with extinction.

Invasive species and other like pests threaten refugia, but it is climate change that may in fact pose a greater threat where heat waves and droughts turn plants into fuel for fire. That could result in refugia becoming less frequently capable of surviving fires that become more intense in their nature. So it is critical to know more about refugia so that a strategy to preserve them can be achieved.