Wildfires are a natural part of many ecosystems, but they can become destructive and less predictable, especially when the system is perturbed. Human activities and climate change lead to interactions with fire dynamics that need our attention.
Wildfire and ecosystems
A number of enormously destructive fires raged around the globe in 2018. Wildfires are an integral part of ecosystems, but human activities and climate change disturb ecosystems and can change fire characteristics and their impacts.
Here, we bring together a collection of research and opinion articles in Nature Geoscience that explore the trends and impacts of wildfires in disturbed ecosystems. In addition to these pieces, we present selected articles published in Nature, Nature Ecology and Evolution, Nature Climate Change, Nature Plants and Nature Communications.
Wildfire and ecosystems
Cumulative wildfires or prescribed burning produce different outcomes for the vegetation, suggest two long-term analyses of fire-affected ecosystems. Climate change and land management practices are altering how ecosystems function.
Fires and logging alter soil composition and result in a significant reduction of soil nutrients that lasts for decades after the disturbance, suggests an analysis of soil samples across a multi-century sequence in mountain ash forests.
Prescribed burning has far less impacts on peat growth and carbon sequestration than previously thought, according to a long-term experiment in fire-managed peat moorlands in England. Managed burning may be a viable strategy to make peatlands more resilient to devastating wildfire.
The amount of carbon stored in peats exceeds that stored in vegetation. A synthesis of the literature suggests that smouldering fires in peatlands could become more common as the climate warms, and release old carbon to the air.
Boreal forest wildfires in North America are more intense and destructive than in Eurasia. Differences in species-level adaptations to fire are primary drivers of these differences in fire regimes.
Climate change has increased the area affected by forest fires in boreal North America. An analysis of the depth of burning in forests and peatlands in Alaska indicates that ground-layer combustion has accelerated regional carbon losses.
Under drought conditions, biomass burning in Indonesia is a disproportionate contributor to the global carbon dioxide emissions from such events. An analysis of Indonesian records of large fires shows that their occurrence is linked to land use and population dynamics, and that the Indian Ocean climate and El Niño both have an equally important influence.
A compilation of wildfire records spanning six continents and 2,000 years reveals global patterns in biomass burning to be temporally linked with changes in climate, population and land use. An abrupt decline in biomass burning beginning about 150 years ago may be related to the expansion of intensive grazing, agriculture and fire management activities.
Wildfires have been a natural part of the Earth system for millions of years. A new charcoal database for the past two millennia shows that human activity increased biomass burning after AD 1750 and suppressed it after AD 1870.
Boreal forest fires tend to be more intense and lethal in North America than Eurasia. Differences in tree species composition explain these differences in fire regime, and lead to contrasting feedbacks to climate.
Extreme wildfire events are on the increase, particularly in anthropogenic, suburban landscapes. Particular areas of concern are the subtropical Southern Hemisphere and European Mediterranean Basin.
Global wildfires can have severe societal implications and economic cost and have been strongly linked to climate. Here, the authors analyse daily global wildfire trends and show that, during the past 35 years, wildfire season length has increased by 18.7% over more than a quarter of the Earth’s surface.
A meta-analysis and field data show that frequent fires in savannas and broadleaf forests decrease soil carbon and nitrogen over many decades; modelling shows that nitrogen loss drives carbon loss by reducing net primary productivity.
An international monitoring initiative is crucial for understanding wildfires and reducing their damage, says David Bowman.
The boreal forest is being transformed by changes in its climate–fire regime. Analysis now shows that lightning drives year-to-year and long-term ignition and burned area trends in boreal North America.
Fossil records suggest that the Amazon rainforest in the pre-Columbian era was home to polyculture agroforestry, with multiple annual crops providing subsistence for indigenous groups who shaped the Amazon as early as 4,500 years ago.
Globally, flora, fauna and many indigenous cultures have evolved to coexist sustainably with fire. We argue that the key to sustainable contemporary human coexistence with wildfires is a form of biomimicry that draws on the evolutionary adaptations of organisms that survive (and flourish) in the fire regimes in which they reside.
Deforestation carbon emissions from the Brazilian Amazon have declined steeply, but how much drought-induced forest fire emissions add to this process is still unclear. Here the authors show that gross emissions from forest fires are more than half as great as those from deforestation during drought years.
Exacerbated fires in Mediterranean Europe due to anthropogenic warming projected with non-stationary climate-fire models
A warmer and drier climate will affect wildfire activity but the climate-fire relationship could change under warming. Here the authors use models with a non-stationary climate-fire relationship to show that to avoid doubling the burned area in the coming decades we must stay below 1.5 °C Paris target.