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Fire has a major influence on the development and management of many of the world's forests. Some forest ecosystems have evolved in response to frequent fires from natural as well as human causes, but most others are negatively affected by wildfire.

Every year millions of hectares of the world's forests are consumed by fire, which results in significant loss of life and livelihoods and enormous economic losses from destroyed timber and infrastructure, the high costs of fire suppression, and loss of environmental, recreational and amenity values. FAO’s Global Forest Resources Assessment 2010 noted that, on average, one percent of all forests, or 19.8 million hectares, were reported to be significantly affected each year by forest fires. In addition to direct losses, the associated soil erosion, site deterioration and subsequent difficulties in re-establishing the forest due to the dry climate and poor soil conditions have major impacts on the forest sector.

Forest structure may be abruptly changed by intense canopy fires, which burn leaves and small branches and which are accompanied by surface fires that consume forest floor and understory vegetation. Notably, most of the larger tree boles are not burned, even if killed, and they often remain standing for 10–50 years after a fire. Such residual living and dead organic matter are important for wildlife habitat, nutrient dynamics, ecosystem function and forest recovery, though it may provide a breeding substrate for insect pests thus possibly leading to devastating outbreaks.

In recent decades a notable increase of large wildfires or mega-fires has been noted in all regions of the world. Mega-fires are the most costly, most destructive and most damaging of all wildfires. Not always a single wildfire, they are sometimes a group of multiple fires across a large geographic area. The risk of their occurrence likely increases as droughts deepen, fuels accumulate, and landscapes become more homogeneous. Mega-fires are often extraordinary for their size, but they are more accurately defined by their complex, deep and long-lasting social, economic and environmental impacts. They severely impact local communities and also have serious regional or global consequences. Environmental impacts include interrupting or adversely altering energy, water, nutrient and carbon cycles, declines in biodiversity, increased carbon emissions, and weed invasion.