Modeling the Influence of Eucalypt Plantation on Wildfire Occurrence in the Brazilian Savanna Biome

Abstract

In the last decades, eucalypt plantations are expanding across the Brazilian savanna, one of the most frequently burned ecosystems in the world. Wildfires are one of the main threats to forest plantations, causing economic and environmental loss. Modeling wildfire occurrence provides a better understanding of the processes that drive fire activity. Furthermore, the use of spatially explicit models may promote more effective management strategies and support fire prevention policies. In this work, we assessed wildfire occurrence combining Random Forest (RF) algorithms and cluster analysis to predict and detect changes in the spatial pattern of ignition probability over time. The model was trained using several explanatory drivers related to fire ignition: accessibility, proximity to agricultural lands or human activities, among others. Specifically, we introduced the progression of eucalypt plantations on a two-year basis to capture the influence of land cover changes over fire likelihood consistently. Fire occurrences in the period 2010-2016 were retrieved from the Brazilian Institute of Space Research (INPE) database. In terms of the AUC (area under the Receiver Operating Characteristic curve), the model denoted fairly good predictive accuracy (AUC ≈ 0.72). Results suggested that fire occurrence was mainly linked to proximity agricultural and to urban interfaces. Eucalypt plantation contributed to increased wildfire likelihood and denoted fairly high importance as an explanatory variable (17% increase of Mean Square Error [MSE]). Nevertheless, agriculture and urban interfaces proved to be the main drivers, contributing to decreasing the RF's MSE in 42% and 38%, respectively. Furthermore, eucalypt plantations expansion is progressing over clusters of high wildfire likelihood, thus increasing the exposure to wildfire events for young eucalypt plantations and nearby areas. Protective measures should be focus on in the mapped Hot Spot zones in order to mitigate the exposure to fire events and to contribute for an efficient initial suppression rather than costly firefighting.The savanna is a very important biome due to its large geographic extent, high levels of biodiversity and intense fire activity [6,7], being among the most frequently burned ecosystems in the world [8,9]. At the same time, this fire-prone biome is perceived as favorable land for agricultural expansion, which has emerged as a key factor transformation for this region [10]. Recently, Brazilian savanna, also known as 'Cerrado', is experiencing a significant land use transformation, with the native vegetation being replaced by intensive forestry, agricultural lands and urban areas [11]. The probability of a fire to occur depends on the occurrence of an ignition source (either human-related or natural) and favorable burning conditions within the environment [12]. In the Brazilian savanna, fire is used by humans as a management tool for vegetation removal, maintain grasslands, burn off agricultural residues or clean farm borders [6,13]. Nonetheless, fi...

Identifying and managing disturbance‐stimulated flammability in woody ecosystems

“…Studies in several parts of the world such as Brazil, Chile, and Spain have revealed that fast‐growing, densely stocked, tree plantations can support large‐scale, high‐severity wildfires (Gómez‐González, Ojeda & Fernandes, 2018; McWethy et al ., 2018, de Castro Galizia & Rodriguez, 2019). For example, in the decade between 1996 and 2005, 3–4% of Portugal's eucalypt and pine plantations burnt annually (Rego, Louro & Constantino, 2013).…”

Adaptation and resilience of agricultural systems to local climate change and extreme events: an integrative review

“…-High temperatures along with low relative humidity and soil moisture are conditions that increase the risk of fires, and systems with trees potentially minimize these impacts and therefore reduce fire risks, such as on crop-livestock-forest integration and livestock-forest integration (Kichel et al 2014), agroforestry system (Tscharntke et al 2011) and native forest (White & Silva 2016); -Trees, shrubs and litter may behave as fuel for wildfires, and planted forests are particularly listed as a potential land use that increases fire risk (Galizia & Rodrigues 2019); -At a local scale, incorporating trees may be hydrologically advantageous in the long term (Zimmermann et al 2006), but not immediately after implementation (Ferraz et al 2014). In fact, water gains are from improved infiltration and higher storage of water in the soil and aquifers that overcome the evapotranspiration losses (Bruijnzeel 2004); -Crop-livestock integration systems in the Cerrado region, in areas with longer dry spells (15 to 31 days) during the growing season, showed a greater resilience with little change in yield (Alvarenga et al 2021); -Intercropping systems with trees may be critical for crops during a drought event, due to the higher capacity of water absorption by trees (Souza et al 2017).…”

Assessing expected economic losses from wildfires in eucalypt plantations of western Brazil

“…For instance, a single wildfire in 2017 destroyed more than 1,300 hectares of eucalypt plantations, causing an estimated economic loss of 5 million US$, and threatening several communities across the studied extent (Galdiole, 2017). Fire is culturally used to clear and open large areas for agriculture and extensive livestock breeding; thus, humans are responsible for most fire ignitions (Eva and Lambin, 2000;Galizia and Rodrigues, 2019;Jepson, 2005;Mistry, 2002). The region is characterized by low population density (4.8 inh km -²) with a predominance of rural settlements (IBGE, 2012).…”

“…Model outcomes suggested that fire occurrence was mainly explained by the proximity to agricultural and urban interface areas. See Galizia and Rodrigues (2019) for further details about the methods and model performance. Based on the aforementioned ignition probability grid, we generated a set of spatially-balanced 50,000 ignition points over burnable areas to saturate the landscape with wildfire (Stevens and Olsen, 2004).…”