Teaming Drought with Wildfires: EU Researchers Suggest New Data for Forest Weather Index

ASTER image acquired September 4 over the western coast of the Peloponnesus Peninsula. In the Bands 6-3-1 composite, burned areas appear in dark red, and unburned vegetation is green. Credit: NASA/GSFC/METI/Japan Space Systems, and U.S./Japan ASTER Science Team.

An estimated 4,000 people lost their homes, and more 60 deaths were reported in the worst fires ever to occur in Greece. This ASTER image was acquired September 4 over the western coast of the Peloponnesus Peninsula. In the Bands 6-3-1 composite, burned areas appear in dark red, and unburned vegetation is green. Credit: NASA/GSFC/METI/Japan Space Systems, and U.S./Japan ASTER Science Team.



In the summer of 2003, 18 people died and more than 500,000 acres of forests and farmland were destroyed in fires in Portugal, marking the country’s worst fire season on record. These fires raged on the heels of an extreme heat wave – one meteorologists called a 500-year event – that swept over Europe and took the lives of more than 70,000.

Forest fires in the European Union (EU) kill up to 20 people a year on average, including firefighters and civilians who can’t escape the flames, says Jesús San-Miguel-Ayanz, leader of Forest Data and Information Systems Unit in the EU’s Joint Research Centre (JRC). These infernos cause significant economic damage by destroying homes, businesses and other structures, and create health risks for people with respiratory problems. The environmental impact from fires is significant as well: Burned forests have negative impacts on animal and plant biodiversity, on soils, and on water resources, San-Miguel-Ayanz said.

“Since the 1990s, we have observed a clear decreasing trend in forest fires, but that doesn’t mean they are causing less damage,” he said. Noting Portugal’s 2003 fire and a huge series of fires in Greece that killed more than 80 people in 2007, San-Miguel-Ayanz said that many of the most damaging fires in the EU occur in the Mediterranean Region during the summer months, when seaside towns are packed with tourists. “We have forest fires all over Europe,” San-Miguel-Ayanz said, but the forests in the center of the continent are much denser and smaller than in the Mediterranean. The amount of dried vegetation ready to ignite is smaller as well. “Fires in the mid-continent may escape into the forest but they are put out quickly,” he added.

Web-based fire inventory

The European Commission (EC) is taking fire risk seriously and has created a web-based fire warning and assessment portal. Known as the European Forest Fires Information System (EFFIS), the site provides comprehensive forest fire information aimed at a wide audience in all 27 EU member states.

Specifically, the EFFIS highlights forest fires and burned areas, provides daily forecasts of fire danger, and identifies fire hot spots, notes Daniel McInerney, a post-doctoral researcher at JRC’s Forest Resources and Climate Unit.

Another portal, the European Forest Data Center (EFDAC), focuses on forest maps, and forest health.

This information can improve each country’s ability to forecast when and where a fire is likely to break out. It also can guide country-level decisions about where to spend forest firefighting and response resources – a difficult task in tough economic times.

“In the EU … each country has a different fire risk and fire damage assessment information system, different definitions of forest, and different means of measuring biomass, so it’s very important to have an integrated system that tries to harmonize the data that is collected,” San-Miguel-Ayanz said.

At the EuroGEOSS 2012 Conference in Madrid, researchers showed for the first time that drought data – collected with the European Drought Observatory (EDO) – can be integrated into existing forest fire index data.

A photo of a post-forest fire pine plantation (Mediterranean forest) taken in 2005, in Sestri, Genova. Credit: Dr. Andrea Camia (EC-JRC) .

A photo of a post-forest fire pine plantation (Mediterranean forest) taken in 2005, in Sestri, Genova. Credit: Dr. Andrea Camia (EC-JRC) .



Drought is a creeping hazard, and scientists find that it’s hard to finger when a drought begins and to predict when it will end. Yet drought is a normal part of the climate in all regions of the world. Drought contributes to fires in the obvious ways: Weeks and months of little rainfall leaves the soil parched and vegetation waterless, and creates piles of dried grass, leaves, twigs and trees ready to ignite. Scientists also say that climate change is one contributor to drought: the EC’s JRC notes that climate change studies indicate a trend toward increasing climate variability, most likely resulting in more frequent drought occurrences in Europe.

With this in mind, the JRC established a European Drought Observatory (EDO) as a means to assess, monitor and forecast droughts on a continental level in Europe.

Adding drought to fire data

McInerney, along with Hugo Carrao, a researcher with the JRC’s Institute for Environment and Sustainability; and Barbara Hofer, now an assistant professor at the University of Salzburg, Austria; conducted the study showing that drought data can improve existing forest fire index data. The analysis was done as part of the EuroGEOSS FP 7 project, which is designed to advance Europe’s contribution to the Global Earth Observation System of Systems.

The scientists used data collected in 2009 during fires on the Iberian Peninsula. The Peninsula’s forest fire season ranges from July 1 through Sept. 30. The summer-time Mediterranean climate of high temperatures and almost no rain puts plants under extreme stress: When their moisture derceases their flammability increases, the team wrote in their paper. They applied this data to an analysis of the current Fire Weather Index (FWI) to test their hypothesis that information on drought conditions that occur outside the summer’s fires season would improve forest fire risk assessment. This research is currently under review for publication in a special edition of the Journal of Spatial Data Infrastructure Research.

The researchers based their findings on three data sets: the burned areas mapped by the EFFIS Rapid Damaged Assessment for this region, the EFFIS FWI, and the Standardized Precipitation Index (SPI).

The FWI is a composite index that provides information on the wetness of the vegetation derived from the accumulated precipitation of the previous 24 hours, as well as data on the temperature, wind speed, relative humidity and rain. Fire managers rely on the FWI to tell them when to expect that conditions will favor fire. SPI, on the other hand, measures the intensity of monthly deviations in accumulated rainfall changes, making this a second tool for fire managers on the lookout for conditions that can support a fire.

Most drought analysis computes precipitation levels and drought potential for short periods of one to three months, the researchers note. Because the Iberian Peninsula has almost no rain for the three-month summer period, the SPI computed for this short period would not show drought, since lack of rainfall here is not a stark change, or deviation, in the region’s normal weather pattern, according to the paper. So the scientists employed SPI data for a 24-month period (SPI-24) and were able to show the relationship between long-term drought conditions and the occurrence of burned areas.

A plume of smoke drifts westward over the Atlantic Ocean from a massive forest fire in southwestern Portugal in this Moderate Resolution Imaging Spectroradiometer (MODIS) image from the Aqua satellite.  Credit: Jeff Schmaltz, MODIS Rapid Response Team, NASA GSFC.

A plume of smoke drifts westward over the Atlantic Ocean from a massive forest fire in southwestern Portugal in this Moderate Resolution Imaging Spectroradiometer (MODIS) image from the Aqua satellite. Credit: Jeff Schmaltz, MODIS Rapid Response Team, NASA GSFC.



For every month in 2009, the researchers gauged the relationship between the location of the burned areas and the water supply conditions when the fire raged. Looking at the SPI-24, the results showed that nearly 70 percent of all forest fires took place in areas with extremely dry conditions. When they added “moderately dry” areas from SPI-24 to their analysis, they found that the percentage of burned areas under dry conditions zoomed to almost 90 percent.

Finally, the analysis showed that only 0.5 percent of forest fires happened in areas where the SPI-24 values indicated wet conditions. “This is an important insight,” the scientists wrote, because it indicates that these fires were automatically excluded from potential forest fire danger when using SPI data for short time scales.

Going a step further in their analysis, the team calculated the SPI-24 values for the months outside the summer fire season – particularly in March and October. The FWI for these months, (based on the wetness and other climatic conditions over the past 24 hours), showed fire danger to be low to moderate in the burned areas. In contrast, the SPI-24 values in the burned areas stayed at almost the same pattern over time, showing severely to moderately dry conditions.

The researchers concluded that incorporating SPI-24 data to EU fire danger assessments would be a more accurate determinant of what the fire manager can expect.

Our “results were promising and opened the way to further research along these lines,” Hofer said.

But whether the EC will add drought information to its fire index is unclear, according to McInerney . “There is a possibility that drought information could be integrated in the medium term future to improve the FWI,” he said, “but this is yet to be determined.”

Catherine M. Cooney is a Washington D.C.-based science writer and editor who has covered environmental, energy, and health issues for scientific journals, daily news sites, and industry publications. She has written about Congress and federal agencies and was a reporter and the news editor for the journal, Environmental Science & Technology. She launched her freelance career in 2009 and has since written for Environmental Health Perspectives, InsideClimate News, Chemical & Engineering News and other publications.


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