Analysing eucalypt expansion in Portugal as a fire-regime modifier

Area of Science:

• Forest Ecology
• Fire Science
• Environmental Management

Background:

• Blue gum (Eucalyptus globulus) plantations dominate Portugal's forests, raising concerns about increased fire activity due to their flammable fuel complex.
• The role of eucalypt plantations in Mediterranean fire regimes is debated, especially after recent catastrophic wildfires in Portugal.

Purpose of the Study:

• To investigate the effects of eucalypt forestation on burned area, fire size, and fire severity in Portugal.
• To assess whether eucalypt expansion has modified the fire regime in Mediterranean climate regions.

Main Methods:

• Analysis of fire and vegetation mapping, fire weather data, satellite imagery, and national forest inventory data from 1980-2017.
• Statistical examination of the relationship between eucalypt presence and fire metrics, including burned area, fire size, and severity.
• Comparison of fuel accumulation and fire behavior in eucalypt stands versus maritime pine forests.

Main Results:

• Eucalypt burned area averaged 12.5% of total burned area and did not increase with eucalypt expansion.
• Fires originating in eucalypt stands were less likely to become large, and large fire size was independent of forest composition.
• Forest type had a minor influence on mega-fire severity, accounting for only 1.4-8.6% of surface fuel hazard variation. Conversion to eucalypt stands generally implied lower fuel accumulation.

Conclusions:

• Eucalypt forestation in Portugal has not demonstrably modified the fire regime in terms of burned area, fire size, or severity.
• While eucalypt plantations present a trade-off between spotting potential and crown fire likelihood, they do not appear to be a greater fire threat than native vegetation.
• The increasing area of undermanaged and abandoned blue gum stands is a future concern, requiring further research on post-fire regrowth impacts.