Towards the Iberian Peninsula

Bordered by the Atlantic Ocean and Spain, Portugal’s diverse climate, geography, and ecosystems can be attributed to its unique location. The country is made up of 92,090 km² of diverse ecosystems, approximately the size of the state of Maine. The country’s diverse landscape is illuminated by Figures 2 and 3. The former depicts an active fumarole, which is an opening near a volcano that expels gases, and the latter shows a highly flammable coastal ecosystem- similar to those of California, Florida, and Australia.

Figure 2. Fumaroles along a waterway created by springs in central part of Furnas village on Sao Miguel Island, Azores, Portugal

Figure 3. Reminiscent of Southern California’s Coastal Sage Scrub, a scenic Atlantic trail named Costa Verde attracts visitors year-round.

Why Does It Matter?

What’s Going On?

In Portugal, wildfires larger than 100 ha in size make up less than 1% of fires but account for about 75% of the total area burned (DGRF 2006)(Figure 4). Not only that, but wildfires in Portugal have burned an area equivalent to 50 percent of the total country area in the past 3 decades alone (Marques et al. 2011). Wildfires have essentially become more common as the Mediterranean experiences less summer rainfall and higher annual summer temperatures due to climate change (Piñol 1998; Pausas 2004; Brotons et al. 2013).

Figure 4. A typical Football field or the inside area of a Track field are approximately one hectare in size

Who Is Responsible?

Keeping in mind that wildfires are becoming increasingly more dangerous and frequent, I hope to uncover some of the factors contributing to these dangers. Portugal’s diverse forest ecosystems aid in achieving this goal. A major factor contributing to increased wildfires, apart from climate change, is forest management techniques- specifically when talking about fuel load management (Brotons et al 2013). For this reason, exploring Portugal’s different forest types can aid in drafting efficient ways to keep wildfires at bay.

Portugal can be characterized by the different ecosystems across the country. These diverse ecosystems differ in susceptibility to forest fires because they have different physical compositions and structures. A main indicator of forest type is the different heights of the canopy as well as the spacing between each individual plant (Figure 5). These particular attributes are of importance because fires readily depend on the availability of flammable biomass. Furthermore, wildfires rely on dry conditions and high temperatures as I mentioned above.

Figure 5. Forests can be better undestood in terms of their structure. Forests can have heavily concentrated plants or dispersed individuals as well as tall canopies versus short stocked plants.

Rainy winters are dispersed unevenly across the Mediterranean, and hot, dry summers dominate for over half of the year. Much like in Australia and California, wildfires thrive on the prevalence of biomass following rainy seasons. Figure 6 depicts a wildfire in the hills of Monchique; the image juxtaposes the quiet, dark streets of the town with the raging fire on the hill.

Figure 6. Wildfires swept across Monchique in the south of Portugal today in the wake of a heatwave

Data

As previously mentioned, Godinho-Ferreira et al. (2005) actively recorded and analyzed the different forest types across Portugal. His team contributed to the Portuguese National Forest Inventory (NFI), and his team’s forest data are used to roughly assess relative fire hazards across the country. Using this data alongside the observations and analysis performed by Fernandes (2009), a better understanding of the risks of fire across the Portuguese landscape is possible (Figure 7).

Figure 7. Paulo Fernandes (2009) combines forest structure data and fuel modelling to better describe fire hazards across Portugal

Often, fuel load (i.e. available biomass) is the only factor that can be address when preventing wildfires(Agee and Skinner, 2005). Forest structures and fuel models can be used in unison to best identify which forests are most susceptible to wildfires. Thus, giving us an idea of what areas require the most attention and resources.

The fuel model used here, designed by Rothermel (1972), considers four aspects when determining surface fire propagation. The model looks at general availability of plant litter, herbs, shrubs, and the slashing of plants. This model has been edited and improved over time to obtain a more realistic estimate of fire characteristics for specific fuel types (Andrews et al. 2005)

Forests across the globe can be physically characterized by their overall plant structures, species population densities, and concentration of individual species across the landscape. More generally, they each have a specific “forest structure”. Forest structure is vital because depending on the structure, wind patterns and available fuel loads differ.

Forest Structures

• Open and Tall

Figure 8. Open and Tall forest composed of Eucalyptus trees

• Open and Low

Figure 9. Open and Low Forest composed of Quercus suber

• Closed and Tall

Figure 10. Closed and tall Forest made up predominantly by Pinus Pinaster

• Closed and Low

Figure 11. Closed and Low Forest composed of P. pinaster

Each of the forest types can be evaluated using three fire behavior descriptors: rate of spread, fireline intensity, and crown fire potential.

* Rate of Spread: How fast fire spreads in a specific area

* Fireline Intensity: Rate of spread estimate x fuel load x heat content

* Crown Fire Potential: Probability of forest fires spreading from treetop to treetop

By looking at the four different types of forest structure in relation to Fire Spread, Intensity, and Crowning, we get a better idea of which forest structures have the highest risk of seriously dangerous fires.

* Generally, both open and closed low structures have the highest risk of crowning, fire spread, as well as the highest fire intensity

* Of the tall systems, the closed structures have higher risks of crowning, fire spread, and higher fire intensity, but these values differ only slightly.

In conclusion, these figures suggest that flammability is more closely related to stand structure, rather than cover type. Open structures have a lower understory layer and less fuel loading where closed structures tend to be more tightly packed therefore more capable of spreading fires quickly.

Furthermore, fuel load is more important than rate of spread in regards to fireline intensity, and crown base height is more important than fireline intensity in determining variations in crowning potential for the different forest types.

* Stand thinning and pruning increases fire spread via changes in within-stand wind movement.

* Surface fuel treatments can favor fire suppression and decrease fire severity.

* Vertical discontinuity is vital in avoiding crown fire.

With these ideas in mind, the following can be done to prevent forest fires much more effectively:

Future studies should continue to look at differences in forest structures across the globe to piece together missing information. Given that Portugal has a similar climate to places like California and Australia, it is a valuable case-study when looking into the future of wildfire management around the world especially as climate change poses novel threats. Forest management techniques are currently employed by governments, but these techniques have shown to sometimes have negative long-term effects, which factor into more extreme wildfires. More research should go towards having a more robust understanding of forests, forest structures, available fuel loads, wildfires, and how these wildfires impact communities, both urban and rural. Wildfires are only becoming more dangerous and expensive, so ignoring them would be a grave mistake from our part.