Post-fire forest regeneration prevented by vicious cycle of rising temperatures, wildfires

Longer and larger forest fires are contributing to land surface warming, a major new study reveals. Summer 2024, marked by deadly wildfire episodes, was officially Europe’s warmest on record, and it’s getting worse.

The study, published in Nature, analysed over a decade of satellite data on wildfire events from 2003 to 2016 in northern temperate and boreal forests. Scientists found a widespread warming effect one year after the fire events.

They calculated that fire size amplified surface warming in North America and eastern boreal Asia. Evapotranspiration and surface reflectivity decreased one year after a fire event. It means that less water is released and more incoming radiation is absorbed.

This affects the ability of post-fire forests to regenerate and their species composition, reinforcing the degradation of permafrost and the release of organic carbon from that layer.

It all translates to extreme fires further exacerbating global warming, which will, in turn, lead to more extreme fires, creating a vicious cycle of ever-increasing temperatures.

Solution? Broadleaf trees

While the amplified surface warming effect was not observed in western, central, and southeastern Siberia, as well as eastern Europe, scientists said this is due to these forests being primarily composed of deciduous broadleaf trees.

“Given the projected increase in fire size in northern forests, climate-smart forestry should aim to mitigate the climate risks of large fires, possibly by increasing the share of broadleaf trees, where appropriate, and avoiding active pyrophytes,” they concluded.

For instance, harvested strips of coniferous forests could be replanted with broadleaf trees, which would act as firebreaks to limit the spread of fires in an otherwise uniform coniferous landscape.

Scientists, however, advise caution and careful local-scale planning to increase the share of broad leaves in areas where such forests pose a risk for human-dominated spring fires.

Scorching summer for Europe

While northwestern regions experienced temperatures close to or below average, southeastern areas faced record-breaking heat stress. This was confirmed by the European Union’s Copernicus climate change service on 26 September.

Parts of Europe saw substantial heat waves during the season, but southeastern Europe bore the brunt, with up to 60 per cent more “warm daytimes” than average.

For around two-thirds of the summer, daily perceived temperatures hit at least 32℃. With 66 days recorded, Copernicus’ scientists say this marks the highest number of “strong heat stress” days on record by a significant margin.

The average number of summer days with at least “strong heat stress” is 29 for southeastern Europe as a whole. But in some areas of Greece, western Türkiye, and Spain, “extreme heat stress” occurred.

Hectares burnt in the blaze

These extreme temperatures brought along significant fire damage. According to the Civil Protection Knowledge Network, such episodes were observed in Greece, Türkiye, as well as certain parts of Italy.

Bulgaria, North Macedonia, Albania, Greece and Portugal were also affected by wildfires during the summer season, activating the European Civil Protection Mechanism (UCPM) to fend off fires.

According to the European Forest Fire Information System (EFFIS), a component of the Copernicus Emergency Management Service, more than 85,000 hectares have burned in North Macedonia since the beginning of summer.

Several significant wildfires developed in northern Portugal in recent days, with multiple fatalities and significant damage to land and property. An estimated 135,845 hectares worth of land has burned in the summer blaze.

Replanting after wildfires?

While the European Commission has pledged to plant three billion additional trees by 2030, an ambitious goal, there is no clear focus on replanting forests after wildfire episodes.

As the study published in Nature highlighted, fires affect the ability of a forest to regenerate and also have an impact on the species inhabiting a specific forested area.

Although tree planting is an effective way to combat climate change, strategies should be mindful of the changes in landscape composition and configuration and how these can impact fire propagation.

When selecting tree species for planting, argue experts, the focus should be on natural resilience to future fires, often favouring native resprouting species. The objective is to develop resilient landscapes capable of withstanding and recovering from the impacts of climate change, particularly the risk of wildfires.

[By Xhoi Zajmi I Edited by Brian Maguire | Euractiv's Advocacy Lab ]