Wildfire
An estimated 340–370 million ha of the Earth’s land surface is affected by fire annually (equivalent to just less than half the land area of the Australian continent).26, 27 An estimated 383 million ha (based on Moderate Resolution Imaging Spectroradiometer [MODIS]j data) was burnt in 2023.28 Note, however, that the actual area burnt likely exceeded this amount, with measurement incomplete due to technical limitations and challenges associated with the detection of small fires, temporal coverage and cloud cover. In sub-Saharan Africa, for example, Sentinel-2 data (at 20 m spatial resolution) indicated a total burnt area in 2019 that was 120 percent greater than that estimated from MODIS data (with a resolution of 500 m). This confirms that fires not mapped by MODIS are yet to be accounted for in global analyses.29
Fire is a widely used land management tool for various socioecological purposes,30 but uncontrolled fires – wildfires – can have significant negative impacts at the local, national and global levels. The frequency and intensity of wildfires is increasing, including in areas not previously affected, particularly due to climate change and land-use change. For example, boreal fire has previously been responsible for about 10 percent of global carbon-dioxide emissions due to wildfires; in 2021, however, such fires reached a new high (driven largely by extended drought, which caused an increase in fire severity and fuel consumption) and accounted for nearly one-quarter of total wildfire emissions.31 There was a record-breaking increase in fire activity in the Northern Hemisphere in 2023.32 In Canada, an estimated 6 868 fires burnt 14.6 million ha,33 which was more than five times the 20-year average.
An increase in the frequency and intensity of wildfires, itself largely a consequence of climate change, can accelerate positive feedback loops in the carbon cycle, presenting a challenge for global climate-change mitigation efforts.34 Satellite observations indicate that, in 2023, fires emitted 6 687 megatonnes of carbon dioxide globally,k, 28 which was more than double the estimated carbon dioxide emissions by the European Union due to the burning of fossil fuels in that year (2.6 billion tonnes).35 Combining Indigenous and other traditional approaches to fire management with modern technologies and knowledge is an emerging innovation in various landscapes around the world.
Pests
Climate change is making forests more vulnerable to invasive species, causing changes in their geographic distribution and seasonal phenology and in aspects of population dynamics.36 Insect pests and disease pathogens can reduce tree growth and survival, wood quality and the provision of ecosystem services such as carbon sequestration. Forests worldwide are vulnerable to invasions by species from a wide range of taxa.37 Climate change and poor forest management practices are also leading to increases in outbreaks of native insect pests, such as bark beetles.38
The threat to forests posed by pests is considerable: for example, pine wood nematode has caused significant damage to native pine forests in China, Japan and the Republic of Korea, with the Korea Forest Service reporting the loss of 12 million pine trees due to the nematode between 1988 and 2022.39 In the United States of America, 25 million ha of forestlands are projected to experience losses exceeding 20 percent of host tree basal area due to insects and disease through to 2027.40
The monitoring of forest degradation, including outbreaks of insect pests and disease, is at an early stage globally. It is also difficult to quantify the economic cost of damage, which encompasses timber losses, the cost of tree replacement, and impacts on ecosystem services and socioeconomic outcomes for local communities.39 Technological and policy innovations are needed to better understand and address the interrelated drivers of forest disturbances such as fire, pests and diseases – and the effects of climate change on these – and to take more-integrated approaches to their management and enhance the resilience of forests and forest-dependent people.40
