“El Niño” events increase seasonal wildfire danger in Ecuador

Abstract

Weather is a key driver of catastrophic wildfire seasons. On a global scale, different phases of the El Niño-Southern Oscillation, “El Niño” or “La Niña”, modulate weather and therefore wildfire activity. Ecuador is one the most biodiverse countries in the world and wildfires produce severe impacts to its ecosystems. This investigation explores for the first time the relationship between wildfire weather and El Niño-Southern Oscillation in the tropical Andes. Wildfire weather variability has been quantified using seasonal metrics of the McArthur Forest Fire Danger Index. The calculation of this index requires weather station data that were only available since 1997. Therefore, the availability of data was extended using the Twentieth Century Reanalysis Project to cover the period 1963-2010. Bushfire weather in the seasons April-May-June and July-August-September show significant correlations with the NINO3.4 index (r=0.37,p=0.003, n=47 and r=0.4, p=0.001, n=47 respectively). Additionally, a Chi-squared test showed that every extreme wildfire season in this region was linked to an ‘El Niño’ event. Our results demonstrate that ‘

Introduction

Wildfires are a global phenomenon that produces severe impacts (Luke 1978, Conard 1997, Morton 2003). Catastrophic wildfire events claim lives (Haynes 2008, Haynes 2010), degrade the environment (Shakesby 1993, Stephens 2004, Lane 2010) and destroy building infrastructure (Morton 2003, McAneney 2009, Crompton 2010). Wildfires also contribute to biodiversity loss (Kodandapani 2008, Pastro 2011) and affect the climate (Conard 1997). They are part of the natural evolution of vegetation ecosystems (HaynesBradstock 2012). However, human actions amplify the impact over people, nature and infrastructure (Pausas 2011). In fact, wildfires have a strong anthropogenic ignition pattern. In addition, population growth in rural areas increase human vulnerability to this hazard. The threat of wildfires have encouraged extensive research on the behavior of its precursors.

Weather is one of the key components that contributes to wildfire activity (Powell 1983, Williams 1999, Mills 2005, Haines 1988, Mccaw 2007, Dowdy 2012, Engel 2013). Wildfire weather refers to the meteorological influence over wildfires over a period of time —usually within days—. Common variables associated with wildfire weather are temperature, relative humidity, wind speed and precipitation (Bo