O. Viedma | University of Castilla-La Mancha (original) (raw)

Papers by O. Viedma

An ensemble of multi-scale (regional to local) simulations of potential land use and land cover c... more An ensemble of multi-scale (regional to local) simulations of potential land use and land cover change (LULCC) for the EUMed region was conducted using future projections of climate and socioeconomy. The aim was providing robust estimates of expected changes of land cover in the short- to long-term future. The combination of land cover and climate changes leads to an increase of fire hazard and eventual fire risk. Simulations allow anticipating future change in land cover patterns at regional level as well as discontinuous urban areas and rural-urban interface (RUI) at local scale. Change in land cover, urban sprawl and modifications in spatial structures must be monitored and foreseen to facilitate fire risk prevention and mitigation.

Agriculture, Ecosystems & Environment, 2015

Past the middle of the 20th century, forest fires started to increase markedly in the Mediterrane... more Past the middle of the 20th century, forest fires started to increase markedly in the Mediterranean countries of southern Europe. Hazardous land-use and land-cover (LULC) changes are considered major drivers of increased fire-hazard and fire risk. However, the contribution of various LULC changes to increased fire-hazard, as well as the role of environmental or socioeconomic factors in driving them, including its changing role over time, are poorly known. Understanding how changes in socio-economics in interaction with other factors modify landscape fire-hazard and risk is a major priority in fire-prone areas. Here we determined changes in fire-hazard through time, focusing on the contribution of agriculture abandonment to it, and on the changing role of its driving factors, in a large (56,000 km 2) rural area in West-Central Spain. The study period covers from 1950s to 2000. LULC maps at different time steps (1950s, 1978, 1986 and 2000) were available, as well as environmental and socioeconomic information at various scales. We analyzed trends in LULC change, focusing on those altering fire-hazard, and used general linear models (GLM) with generalized linear mixed models (GLMM) to account for the effects of variables at different spatial scales in determining changes leading to shifts in fire-hazard. We found that the proportion of hazardous LULC types increased twofold (26-42%) from 1950s to 2000. Until 1986, agriculture abandonment was the dominant LULC change leading to increased fire-hazard. Post-1986, LULC changes were mainly driven by deforestation due to fires and densification caused by natural vegetation dynamics. Models showed that the first abandoned lands were driven by local environmental and socioeconomic constraints (small farms, in distant locations, in municipalities with low population), whereas later abandonments were driven by non-local ones (large farms, in more productive soils, closer to towns, populations with high unemployment, and higher employment in the services sector). Throughout the entire period, high proportion of wildland vegetation, low mechanization level, and large number of land-holders older than 55 years favored abandonment. This implies that as the population ages, larger, more accessible and productive areas are abandoned, fire-hazard will increase closer to human settlements, increasing the wild-land urban interface and fire risk. 2015 Elsevier B.V. All rights reserved.

Fire severity, understood as a measure of biomass consumption, is a function of dynamical interac... more Fire severity, understood as a measure of biomass consumption, is a function of dynamical interactions between fuel loads and fire propagation conditions (i.e., fire velocity, wind speed and topography, among other). To understand the factors that control fire severity, accurate methods for estimating pre-fire vegetation structure and composition as well as fire propagation conditions are required. Here we analyzed the spatial variability of fire severity in a large fire having different fuel loads (structure and composition), fire propagation conditions and fire history. The study site was a large and mixed severity fire (3.217 ha) occurred in southeast Spain (Yeste, Albacete) from 27th July to 1th August 2017 that reburned part of an old fire occurred in 1994. Fire severity was estimated using RBR (Relativized Burn Ratio) derived from Sentinel 2A images, which were validated with Composite Burnt Index (CBI) field plots (n=18). Pre-fire vegetation conditions were derived from: 1) L...

Remote Sensing of Environment

Forests

Annual Land Use and Land Cover (LULC) maps are needed to identify the interaction between landsca... more Annual Land Use and Land Cover (LULC) maps are needed to identify the interaction between landscape changes and wildland fires. Objectives: In this work, we determined fire hazard changes in a representative Mediterranean landscape through the classification of annual LULC types and fire perimeters, using a dense Landsat Time Series (LTS) during the 1984–2017 period, and MODIS images. Methods: We implemented a semiautomatic process in the Google Earth Engine (GEE) platform to generate annual imagery free of clouds, cloud shadows, and gaps. We compared LandTrendr (LT) and FormaTrend (FT) algorithms that are widely used in LTS analysis to extract the pixel tendencies and, consequently, assess LULC changes and disturbances such as forest fires. These algorithms allowed us to generate the following change metrics: type, magnitude, direction, and duration of change, as well as the prechange spectral values. Results and conclusions: Our results showed that the FT algorithm was better than...

Scientific Reports

During the last decades, wildfires have been changing in many areas across the world, due to chan... more During the last decades, wildfires have been changing in many areas across the world, due to changes in climate, landscapes and socioeconomic drivers. However, how the role of these drivers changed over time has been little explored. Here, we assessed, in a spatially and temporally explicit way, the changing role of biophysical and human-related factors on wildfires in a rural area in west-central Spain from 1979 to 2008. Longitudinal Negative Binomial (NB) and Zero-Inflated Negative Binomial (ZINB) mixed models, with time as interacting factor (continuous and categorical), were used to model the number of fires of increasing size (≥1-10 ha, >10-100 ha, >100 ha) per 10 × 10 km cell per year, based on fire statistics. We found that the landscape was rather dynamic, and generally became more hazardous over time. Small fires increased and spread over the landscape with time, with medium and large fires being stable or decreasing. NB models were best for modelling small fires, while ZINB for medium and large; models including time as a categorical factor performed the best. Best models were associated to topography, land-use/land cover (LULC) types and the changes they underwent, as well as agrarian characteristics. Climate variables, forest interfaces, and other socioeconomic variables played a minor role. Wildfires were initially more frequent in rugged topography, conifer forests, shrublands and cells undergoing changes in LULC types of hazardous nature, for all fire sizes. As time went by, wildfires lost the links with the initial fire-prone areas, and as they spread, became more associated to lower elevation areas, with higher solar radiation, herbaceous crops, and large size farms. Thus, the role of the fire drivers changed over time; some decreased their explaining power, while others increased. These changes with time in the total number of fires, in their spatial pattern and in the controlling drivers limit the ability to predict future fires. During the last decades, wildfires have been changing in many areas across the world. While changes in climate are often the main factors 1-3 , changes in landscapes and socioeconomic factors are also associated to such variations 4-6. That is particularly important in areas where humans are the major source of ignitions and of landscape change and its flammability. Hence, addressing how human factors have affected wildfires in recent times is important and challenging, due to its varying nature, together with continuing changes in other fire drivers. At regional and local scales, human factors play a major role in wildfires, overriding in part the role of climate 7,8. Human factors exert a dual effect on fire regime, by either decreasing fires (e.g., suppression policy 9) or increasing them (e.g., Land Use/Land Cover [LULC] changes 10), and can dampen fire-climate relationship at different spatial and temporal scales 8. In the European Mediterranean countries (EUMed), the collapse of traditional rural socioeconomic systems since the second half of the XXth century have caused important landscape and socioeconomic changes, increasing landscape flammability and fire risk 10,11. Specifically, fire risk has increased at both the wildland-urban interfaces (WUIs) and wildland-agrarian interfaces (WAIs), where population and human infrastructures are in contact with forest areas and there is an intense competition between agricultural and forestry activities 12-14. Nonetheless, the effects of those driving factors on wildfires vary across temporal and spatial scales 8,15 , requiring spatio-temporal models capable of simulating the spatial and temporal fire patterns. Several studies at EUMed

Journal of environmental management, Jan 24, 2017

During the last decades, contrasted trends in forest fires among countries around the Mediterrane... more During the last decades, contrasted trends in forest fires among countries around the Mediterranean basin have been observed. In the northern/western countries, Land Use-Land Cover (LULC) changes led to more hazardous landscapes, with consequent increases in fires. This contrasted with fire trends in southern/eastern countries. The recent incidence of large fires in some of the latter prompted the question of whether they are now following the path of their neighbors decades earlier. In this study, we investigated recent LULC changes in southwestern Turkey, focusing on those that could affect fire, and the factors driving them. To this end, LULC maps at different time steps (1975, 1990, 2000 and 2010) were obtained from Landsat images, together with relevant socioeconomic data. Generalized linear mixed models (GLMMs) were applied to assess the effects of socioeconomic and geophysical factors on the dominant LULC changes over time. Over the whole period studied, the most important LU...

International Journal of Remote Sensing, 1994

Journal of Environmental Management, 2011

34 925268800 (Ext. 5469)/fax: +34 925268840 RESUMEN Un año después del fuego, las zonas quemadas ... more 34 925268800 (Ext. 5469)/fax: +34 925268840 RESUMEN Un año después del fuego, las zonas quemadas aparecen dominadas principalmente por herbáceas, y las especies le-ñosas actúan como fuentes de heterogeneidad espacial. Aunque hay un fuerte contraste en la riqueza de especies de plantas entre los espacios abiertos dominados por herbáceas (más ricos) y los dominados por leñosas (más pobres); la riqueza de especies es más alta en un nivel intermedio de cobertura donde se produce una competencia moderada. En este trabajo estamos interesados en evaluar el papel de la cubierta vegetal y la heterogeneidad espacial, medida por una imagen QuickBird, en los patrones de riqueza total de especies de una zona quemada a diferentes escalas lo-cales. El área de estudio se encuentra en el Centro-Oeste de España (Anchuras, Ciudad Real), y se vio afectada por un gran incendio en agosto de 2002. Los datos sobre la riqueza de especies se registraron un año después del fuego en cuadrantes anidados de 1, 2...

Wetlands: Ecology, Conservation and Management, 2010

During the last four decades, around 1,500 km 2 of dry croplands have been transformed, and are n... more During the last four decades, around 1,500 km 2 of dry croplands have been transformed, and are now irrigated in the Upper Guadiana river basin, causing hydrologic overexploitation and wetland desiccation. However, there are no estimations on how anthropogenic stressors have been changing the wetland landscape in the recent past. This chapter focuses on the understanding of how the changes on land-use land-cover (LULC), economic activities and population have driven wetland losses and habitat degradation in the basin from the 1970s. Our results show that 40.5% (2,041.6 ha) of the 5,321 ha of wetlands existing in the early 1970s had disappeared in the last 30 years . Most wetland losses occurred through the period 1978-1990, which registered a rate 127 ha of wetland lost per year. Most affected were floodplain wetlands (47% of total loss) and rain-fed temporary ponds (24%). During the entire period 1978-1999, the loss of wetlands could be significantly related to the loss of natural vegetation, as well as to the reduction of agricultural employment. Habitat quality of wetlands showed a clear pattern of nutrient over-enrichment, as well as a trend towards salinization, the later related to the greater disappearance of most freshwater wetlands (0-2,500 µS cm −1 ). LULC, economic activities and demography explained around 50% of wetland loss and habitat quality deterioration. Until 1990, the pressure of population growth, combined with the agricultural sector, explained the disappearance of most wetland area. From then on, habitat quality has been more impacted in areas where industry and building sectors had more weight in the socioeconomic development (also densely populated watersheds).

Agriculture, Ecosystems & Environment, 2015

Past the middle of the 20th century, forest fires started to increase markedly in the Mediterrane... more Past the middle of the 20th century, forest fires started to increase markedly in the Mediterranean countries of southern Europe. Hazardous land-use and land-cover (LULC) changes are considered major drivers of increased fire-hazard and fire risk. However, the contribution of various LULC changes to increased fire-hazard, as well as the role of environmental or socioeconomic factors in driving them, including its changing role over time, are poorly known. Understanding how changes in socio-economics in interaction with other factors modify landscape fire-hazard and risk is a major priority in fire-prone areas. Here we determined changes in fire-hazard through time, focusing on the contribution of agriculture abandonment to it, and on the changing role of its driving factors, in a large (56,000 km 2 ) rural area in West-Central Spain. The study period covers from 1950s to 2000. LULC maps at different time steps (1950s, 1978, 1986 and 2000) were available, as well as environmental and socioeconomic information at various scales. We analyzed trends in LULC change, focusing on those altering fire-hazard, and used general linear models (GLM) with generalized linear mixed models (GLMM) to account for the effects of variables at different spatial scales in determining changes leading to shifts in fire-hazard. We found that the proportion of hazardous LULC types increased twofold (26-42%) from 1950s to 2000. Until 1986, agriculture abandonment was the dominant LULC change leading to increased fire-hazard. Post-1986, LULC changes were mainly driven by deforestation due to fires and densification caused by natural vegetation dynamics. Models showed that the first abandoned lands were driven by local environmental and socioeconomic constraints (small farms, in distant locations, in municipalities with low population), whereas later abandonments were driven by non-local ones (large farms, in more productive soils, closer to towns, populations with high unemployment, and higher employment in the services sector). Throughout the entire period, high proportion of wildland vegetation, low mechanization level, and large number of land-holders older than 55 years favored abandonment. This implies that as the population ages, larger, more accessible and productive areas are abandoned, fire-hazard will increase closer to human settlements, increasing the wild-land urban interface and fire risk.

incendios, como cualquier perturbación natural, altera la estructura y la distribución espacial d... more incendios, como cualquier perturbación natural, altera la estructura y la distribución espacial de las comunidades vegetales afectadas. Asimismo, estos cambios son modulados por el efecto que ejerce la topografía en la disponibilidad de nutrientes y humedad necesaria para el desarrollo de la vegetación. En este trabajo se plantea analizar si la geoestadística, a través de los semivariogramas, es sensible a los cambios espaciales provocados por los incendios, asi como al efecto de la topografía en el desarrollo vegetal. El estudio se ha llevado a cabo sobre una zona de matorral localizada en la zona Norte de Alicante (Este de España). Para ello, se han seleccionado un conjunto de incendios ocurridos en 1991 y se les ha hecho un seguimiento tres años antes de la perturbación (1989)(1990)(1991) y tres años después (1991)(1992)(1993)(1994). Los resultados obtenidos aplicando los semivariogramas demuestran que tras el incendio el paisaje presenta una clara tendencia hacia la homogeneidad espacial, en cuanto que el tamaño medio de las unidades vegetales mínimas aumenta, mientras que se observan distintas tendencias, en cuanto al grado de variabilidad radiométrica después del fuego, entre los incendios analizados.

Ecosystems, 2014

Identifying what factors control fire severity in large fires is critical for understanding fire ... more Identifying what factors control fire severity in large fires is critical for understanding fire impacts and planning pre-and post-fire management. Here, we determined the role of pre-fire stand structure, directional topography, and burning conditions on fire severity in a large fire (12,697 ha) in Central Spain that burned a Pinus pinaster forest on July 2005. Fire severity was estimated using RdNBR based on Landsat 5 TM images. Forest stand structure was reconstructed by systematically sampling the burned area (n = 236). Burning conditions were established using weather information and a map of fire progression, based on which fire rate of spread and propagation direction were calculated. Topographic features in the direction of the fire-front were derived from a digital elevation model. Boosted regression tree (BRT) analysis was employed to relate each group of variables or the entire set to RdNBR. Fire severity was best explained by burning conditions (cross-validation correlation [CVC] 0.56), followed by pre-fire stand structure (CVC 0.34), and directional topography (CVC 0.17). Combining the three sets of variables, CVC increased to 0.71. Higher fire severity occurred in areas burning upslope, with high fire rate of spread, with heterogeneous and dense stands of P. pinaster and Quercus pyrenaica in the understory, receiving high solar radiation, among other characteristics. Fire severity was the result of interactive relationships between burning conditions, pre-fire stand structure, and directional topography. Thus, determining factors controlling fire severity from static stand structure or topography, as is often done, may not be appropriate.

Agriculture, Ecosystems & Environment, 2015

Remote Sensing of Environment

Forests

Scientific Reports

Journal of environmental management, Jan 24, 2017

International Journal of Remote Sensing, 1994

Journal of Environmental Management, 2011

Wetlands: Ecology, Conservation and Management, 2010

Agriculture, Ecosystems & Environment, 2015

Past the middle of the 20th century, forest fires started to increase markedly in the Mediterrane... more Past the middle of the 20th century, forest fires started to increase markedly in the Mediterranean countries of southern Europe. Hazardous land-use and land-cover (LULC) changes are considered major drivers of increased fire-hazard and fire risk. However, the contribution of various LULC changes to increased fire-hazard, as well as the role of environmental or socioeconomic factors in driving them, including its changing role over time, are poorly known. Understanding how changes in socio-economics in interaction with other factors modify landscape fire-hazard and risk is a major priority in fire-prone areas. Here we determined changes in fire-hazard through time, focusing on the contribution of agriculture abandonment to it, and on the changing role of its driving factors, in a large (56,000 km 2 ) rural area in West-Central Spain. The study period covers from 1950s to 2000. LULC maps at different time steps (1950s, 1978, 1986 and 2000) were available, as well as environmental and socioeconomic information at various scales. We analyzed trends in LULC change, focusing on those altering fire-hazard, and used general linear models (GLM) with generalized linear mixed models (GLMM) to account for the effects of variables at different spatial scales in determining changes leading to shifts in fire-hazard. We found that the proportion of hazardous LULC types increased twofold (26-42%) from 1950s to 2000. Until 1986, agriculture abandonment was the dominant LULC change leading to increased fire-hazard. Post-1986, LULC changes were mainly driven by deforestation due to fires and densification caused by natural vegetation dynamics. Models showed that the first abandoned lands were driven by local environmental and socioeconomic constraints (small farms, in distant locations, in municipalities with low population), whereas later abandonments were driven by non-local ones (large farms, in more productive soils, closer to towns, populations with high unemployment, and higher employment in the services sector). Throughout the entire period, high proportion of wildland vegetation, low mechanization level, and large number of land-holders older than 55 years favored abandonment. This implies that as the population ages, larger, more accessible and productive areas are abandoned, fire-hazard will increase closer to human settlements, increasing the wild-land urban interface and fire risk.

Ecosystems, 2014