A spike in wildfire frequency and amount of area burned in the past decades has been increasingly attributed to factors induced by climate change. Though shifting wildfire regimes are strongly affected by more direct human actions, such as increased rates of arson or the effects of urbanization on rural land use, a study by Dimitrakopoulos et al. (2011), chose to focus on the impacts of drought on wildfire activity in the country of Greece. The study analyzed data from weather stations representing all of Greece over the 37 year period between 1961 and 1997. This time period was chosen because it presented the greatest uninterrupted time interval in the available data. The study sought to prove that an increase in severity of annual and summer droughts has resulted in higher rates of wildfires and the total area burned. The study concluded that there was a statistically significant increase in fire activity and a positive correlation between it and annual drought episodes. It also showed that fire activity has increased significantly since 1978, and that drought played a larger role on fire activity in the more humid and cooler regions of Greece. –Lindon Pronto
Dimitrakopoulos, Alexandros P., Vlahou, M., Anagnostopoulou, Ch. G., Mitsopoulos, I. D., 2011. Impact of drought on wildland fires in Greece: implications of climatic change? Springer Science+Business Media B.V. 2011. Climate Change.
The area studied groups together 17 prefectures into five geographic regions denoted as Northern, Western, Central, Eastern, and Southern Greece. The prefectures used in the study were chosen for the availability of 37 years of data from official meteorological stations. This study represented drought by the Standard Precipitation Index (SPI) and measured the two main phenomena of annual drought (expressed as SPI12) and summer drought (expressed as SPI6). The study identified all prefectures under respective climate types based on precipitation levels and were expressed as “semi-dry, semi-wet, and wet.” Wildfire activity, characterized by number of fires and area burned, was also tracked in all 17 prefectures. Aside from applying SPI values to the entire 37 year period, the study was broken down into two separate sub-periods of 1961–1977 and 1978–1997 for data analysis purposes. Dimitrakopoulos et al. were able to detect several fire regime shifts using the extant data with Change Point Analyzing software; by observing the shifts, the data allowed them to determine that a threshold change occurred in 1977. This was significant for analyzing all data during the second sub-period from 1978 to 1997.
The results confirmed the trend that wildfires had increased steadily from 1961 to 1997 in all areas of Greece. More specifically the Northern, Southern and Western areas exhibited a stronger more significant change than the other two regions. Moreover, there was a significantly higher level of fire activity in the second sub-period, as well as a notable increase in area burned for that period as compared to the earlier sub-period pre 1978. Interestingly, the increased rate of fire occurrences between all the regions was not consistent with the area burned geographically, which depended on the region (climate).
By following the SPI12 and SPI6 values, it was determined that both annual and summer drought episodes increased significantly after 1977 for both the Northern and Western regions. Excluding Eastern Greece, all other areas showed a strong positive correlation between fire occurrence and drought episodes during the entire 37 year period. More specifically, Southern and Central Greece (historically exhibiting the highest level of fire activity) did not correlate with the SPI12 value, indicating that it was most heavily influenced by summer droughts (SPI6) alone. While the different regions correlated with both one another and with summer and annual droughts in different ways, the overall effect was that an increase in starts (new fires) geographically mirrored the greater area burned in the cooler more humid climates when more frequent droughts were present.
The overall trends show that between 1961 and 1997, the mean area burned almost quadrupled in Northern Greece nearly tripling in the other districts, while the number of fires almost doubled in Northern and Western Greece. These implications for a global climate change are echoed by increased fire activity in other parts of Europe as well as the rest of the world. In this study, it is apparent that in Central and Southern Greece (warmer and drier) drought episodes during the summer were most detrimental to fire activity while the other regions exhibited increased fire activity when the annual precipitation levels fell, inducing increased fire behavior in response to lower fuel moistures etc.
One interesting contradiction in the results displayed that between the two sub-periods, drought and fire occurrence correlated more significantly leading up to 1978, while a stronger correlation occurred between drought and area burned in the second sub-period after 1977. Dimitrakopoulos et al. offer the following explanation for why this is so: The contradiction lies in the actual cause of individual fires. During the 1961–1977 period, rural Greece was much more heavily populated and the most common cause of fires was negligence. By the late 1970s, urbanization redistributed the population, effecting rural land use, and apparently resulting in a dramatic increase in arson cases. Furthermore, the common denominator for large fires besides high temperature and low Dead Fuel Moisture Content is wind; arson fires can account for large area burned due to their timing with wind.
In conclusion, during the 37 year period, there was a positive correlation with increase of fire activity and annual drought episodes. In Northern and Western Greece alone, fire activity was influenced by both annual and summer drought episodes (which increased after 1977) as opposed to only the summer ones. A possible result of climate change marked a period of prolonged drought in Greece after 1977, which consequently matches a significant increase in the number of fires and area burned during the second period. Overall, the first sub-period 1961–1977 was characterized by its number of fire occurrences to drought correlation, whereas the second sub-period 1978–1997 exhibited a higher correlation to drought and total area burned. Finally, the effects of climate change (increased drought episodes) had a more profound effect on fire activity in wetter colder regions of Greece where historically fire occurrence and area burned was lower. Increased drought episodes have visually impacted wildfire activity in Greece, while current climate change models suggest that further similar trends will, in the future, result in more severe and frequent fires in the Mediterranean region.