Browsing by Author "Wilson, Adam M."

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    Evaluation of satellite-derived burned area products for the fynbos, a Mediterranean shrubland
    (CSIRO Publishing, 2011-10-17) De Klerk, Helen Margaret; Wilson, Adam M.; Steenkamp, Karen
    Fire is a critical ecological process in the fynbos of the south-western area of South Africa, as it is for all dwarf Mediterranean shrublands. We evaluated the potential of current publicly available MODIS burned area products to contribute to an accurate fire history of the fynbos. To this end, we compared the Meraka Institute’s MODIS burned area product, based on the Giglio algorithm (termed the ‘WAMIS’ product) as well as the standard MODIS MCD45A1 burned area product, based on the Roy algorithm, with comprehensive manager-mapped fire boundary data. We used standard inventory accuracy assessment (number and size of individual burn scars) and confusion matrix techniques. Results showed promise for both burned area products, depending on the intended use. The MCD45A1 had low errors of commission (8.1–19.1%) and high consumer’s accuracy (80.9–91.9%), but relatively common errors of omission, making it useful for studies that need to identify burned pixels with a high degree of certainty. However, the WAMIS product generally had low errors of omission (12.2–43.8%) and greater producer’s accuracy (56.2–87.6%), making it a useful tool for supplementing manager-mapped fire records, especially for fynbos remnants occurring outside protected areas.
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    A hierarchical Bayesian model of wildfire in a Mediterranean biodiversity hotspot : implications of weather variability and global circulation
    (Elsevier, 2010) Wilson, Adam M.; Latimer, Andrew M.; Silander, John A.; Gelfand, Alan E.; De Klerk, Helen Margaret
    In this study we combined an extensive database of observed wildfires with high-resolution meteorological data to build a novel spatially and temporally varying survival model to analyze fire regimes in the Mediterranean ecosystem in the Cape Floristic Region of South Africa (CFR) during the period 1980-2000. The model revealed an important influence of seasonally anomalous weather on fire probability, with increased probability of fire in seasons that are warmer and drier than average. In addition to these local-scale influences, the Antarctic Ocean Oscillation (AAO) was identified as an important large scale influence or teleconnection to global circulation patterns. Fire probability increased in seasons during positive AAO phases, when the subtropical jet moves northward and low level moisture transport decreases. These results confirm that fire occurrence in the CFR is strongly affected by climatic variability at both local and global scales, and thus likely to respond sensitively to future climate change. Comparison of the modeled fire probability between two periods (1951-1975 and 1976-2000) revealed a four year decrease in an average fire return time. If, as currently forecasted, climate change in the region continues to produce higher temperatures, more frequent heat waves, and/or lower rainfall, our model thus indicates that fire frequency is likely to increase substantially. The regional implications of shorter fire return times include shifting community structure and composition, favoring species that tolerate more frequent fires.