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Environmental and human factors influencing fire trends in enso and non‐enso years in tropical mexico
- Román-Cuesta, Rosa Maria, Gracia, Marc, Retana, Javier
- Ecological applications 2003 v.13 no.4 pp. 1177-1192
- El Nino, altitude, case studies, cattle, climatic factors, ecosystems, fire spread, fires, flammability, humans, infrastructure, landscapes, pastures, path analysis, poverty, rain forests, socioeconomic factors, synergism, water stress, Mexico
- Tropical and subtropical areas present the vast majority of contemporary global fires. Despite the human origin of most of these fires, little is known of how environmental and socioeconomic variables contribute to the spatial patterns of fire incidence and burned areas. The tropical Mexican State of Chiapas represents a good case study to analyze these interactions, due to the availability of official data, and its similarities to other tropical countries, in terms of environmental and socioeconomic characteristics. This study evaluates the relative importance of human‐related and environmental variables in determining the distribution of the number of fires and area burned in the tropical State of Chiapas in years of normal and extreme climatic conditions (non‐El Niño vs. El Niño). We have searched for causal relationships among fire, environmental, and socioeconomic variables in Chiapas using path analysis. Results of this study show a major importance of environmental variables in non‐El Niño years, suggesting that the status of the vegetation was the main cause determining fire ignition and fire spread in these years. Contrarily, the observed trends in the El Niño period indicate that fire trends were mainly determined by the presence of ignition agents. In these El Niño years, vegetation is so severely water stressed that, when fire starts, all vegetation types burn, regardless of their flammability properties. The main vegetation types affected by fire in non‐El Niño years were the most flammable ones, such as pine–oak communities, while rainforests burned the most in El Niño years. Altitude, pine–oak communities, and poverty levels played major roles in the arboreal fire incidence in non‐El Niño years, whereas the distribution of pastures appeared as an important variable determining arboreal fire incidence in El Niño years. When all fires were considered (affecting any vegetation layer), almost identical trends were observed, with the incorporation of a new variable influencing the area burned: density of infrastructure. The results of this study strengthen the importance of El Niño years in the conservation of rainforest ecosystems and suggest the existence of synergistic effects involving fires, fragmentation, and certain elements of the landscape, such as cattle pastures, in tropical areas.