Interactions between Climate, Land Use and Vegetation Fire Occurrences in El Salvador

Abstract

Vegetation burning is a global environmental threat that results in local ecological, economic and social impacts but also has large-scale implications for global change. The burning is usually a result of interacting factors such as climate, land use and vegetation type. Despite its importance as a factor shaping ecological, economic and social processes, countries highly vulnerable to climate change in Central America, such as El Salvador, lack an assessment of this complex relationship. In this study we rely on remotely sensed measures of the Normalized Vegetation Difference Index (NDVI) and thermal anomaly detections by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor to identify vegetation cover changes and fire occurrences. We also use land use data and rainfall observations derived from the Tropical Rainfall Measuring Mission (TRMM) data to determine the spatial and temporal variability and interactions of these factors. Our results indicate a highly marked seasonality of fire occurrence linked to the climatic variability with a peak of fire occurrences in 2004 and 2013. Low vegetation indices occurred in March-April, around two months after the driest period of the year (December-February), corresponding to months with high detection of fires. Spatially, 65.6% of the fires were recurrent and clustered in agriculture/cropland areas and within 1 km of roads (70%) and only a 4.7% of fires detected were associated with forests. Remaining forests in El Salvador deserve more attention due to underestimated consequences of forest fires. The identification of these clear patterns can be used as a baseline to better shape management of fire regimes and support decision making in this country. Recommendations resulting from this work include focusing on fire risk models and agriculture fires and long-term ecological and economic consequences of those. Furthermore, El Salvador will need to include agricultural fires in the contribution to national accounts emissions.

Characterizing Predictability of Fire Occurrence in Tropical Forests and Grasslands: The Case of Puerto Rico

“…This result contrasts with other studies that found stronger influences of climate than LULC on fire occurrence when using remote sensors [17,22,50]. An open question remains how different resolution fire data are explained by variables operating at different scales.…”

“…The climatic variables mean daily maximum temperature, mean daily minimum temperature, and mean daily annual precipitation, averaged over the period 2003-2011, were significantly correlated with wildfire occurrence in Puerto Rico. In contrast to other tropical and subtropical countries [22,23], mean annual precipitation was not the most important single influencing factor for fire occurrence. Instead, mean daily minimum temperature and daily thermal amplitude represented by the interaction between temperature maximum and minimum were more determinant for fire occurrence and of special consideration in predicting models.…”

“…Percent forest cover, negatively related to fire occurrence, was the main variable in our study explaining the number of fires per barrio, followed by nonwoody vegetation cover and to a lesser degree, urban cover, both positively related to fire occurrence. The negative relationship between percent forest and fire occurrence confirms patterns observed in other tropical regions [22]. From a subset of the Fire Department data we could determine that grass (GR4 and GR3 fuel models) was the dominant fuel type in Puerto Rico, followed by forest (TU and TL fuel models) (results not shown).…”

“…Current global estimates of fire frequency indicate that over 70% of active fires occur in the tropics [20] and that the size and frequency of fires are increasing every year [10,21]. Among climate variables found to be determinant for fire occurrence in the tropics and subtropics, daily and monthly precipitation and daily relative humidity were negatively associated with fire ignitions [22,23]. In addition to climatic drivers, fires in the tropics are unintended consequence of current land-use practices [21,[24][25][26] that promote the establishment of grass and shrubland communities, which are more flammable and more adapted to fire than evergreen forests [27][28][29][30][31].…”

Changing patterns of fire occurrence in proximity to forest edges, roads and rivers between NW Amazonian countries

“…We only used data with confidence levels over 30 % (nominal and high confidence fires as applied in (Armenteras et al, 2016;Chen et al, 2013a) We standardized fire occurrence by the area in km 2 of the unit of analysis, so we used fire density (number of occurrences per 1000 km 2 ) as a fire variable.…”