Satellite Observations Reveal Decreasing Trend in Global Wildfires
GWPF Observatory, 16 September 2020While wildfires in the Western U.S. continue to rage, satellite observations over the last 20 years have revealed a decreasing trend in global wildfires. What’s going on?
Source: NASA Earth Observatory
As strong winds and hot air continue to propel wildfires across the Western U.S. states of California, Oregon and Washington state, politicians, activists and researchers quarrel violently about the main causes of these disasters and how to reduce the risk of wildfires in the future.
There can be little doubt that drought conditions and high temperatures are exacerbating these wildfires. However, over recent decades human activities such as land management and agriculture, increasing population density and active fire suppression have succeeded in significantly reducing the global areas burned by wildfires, despite the rise in global temperatures.
To understand why some arid and semi-arid regions of the world have managed to reduce wildfires in the face of rising temperatures, such as Mediterranean Europe, while other regions haven’t succeeded to do so, will be crucial to risk reduction policies.
Below we have selected recent research papers, based on satellite observations, which reveal the decreasing trend in global wildfires and the most likely reasons for these encouraging developments.
Global trends in wildfire and its impacts: perceptions versus realities in a changing world
Abstract: Wildfire has been an important process affecting the Earth’s surface and atmosphere for over 350 million years and human societies have coexisted with fire since their emergence. Yet many consider wildfire as an accelerating problem, with widely held perceptions both in the media and scientific papers of increasing fire occurrence, severity and resulting losses. However, important exceptions aside, the quantitative evidence available does not support these perceived overall trends. Instead, global area burned appears to have overall declined over past decades, and there is increasing evidence that there is less fire in the global landscape today than centuries ago. Regarding fire severity, limited data are available. For the western USA, they indicate little change overall, and also that area burned at high severity has overall declined compared to pre-European settlement. Direct fatalities from fire and economic losses also show no clear trends over the past three decades. Trends in indirect impacts, such as health problems from smoke or disruption to social functioning, remain insufficiently quantified to be examined. Global predictions for increased fire under a warming climate highlight the already urgent need for a more sustainable coexistence with fire. The data evaluation presented here aims to contribute to this by reducing misconceptions and facilitating a more informed understanding of the realities of global fire.
A human-driven decline in global burned area
Abstract: Fire is an essential Earth System process that alters ecosystem and atmospheric composition. Here we assessed long-term fire trends using multiple satellite datasets. We found that global burned area declined by 24.3 ± 8.8% over the past 18 years. The estimated decrease in burned area remained robust after adjusting for precipitation variability and was largest in savannas. Agricultural expansion and intensification were primary drivers of declining fire activity. Fewer and smaller fires reduced aerosol concentrations, modified vegetation structure, and increased the magnitude of the terrestrial carbon sink. Fire models were unable to reproduce the pattern and magnitude of observed declines, suggesting they may overestimate fire emissions in future projections. Using economic and demographic variables, we developed a conceptual model for predicting fire in human-dominated landscapes.
For more information & research papers see GWPF coverage of wildfires