Cartografía de usos y cubiertas del suelo del sureste de la Península Ibérica a partir de la clasificación de imágenes Landsat en el quinquenio 2000-2004

Se presenta la metodología utilizada en la obtención de la cartografía de usos y cubiertas del suelo para la zona oriental de Andalucía (ámbito de 29.259 km²) en el quinquenio 2000-2004, empleando el clasificador híbrido y utilizando imágenes Landsat junto con las variables auxiliares. Las áreas de entrenamiento se han obtenido de manera semiautomática a partir del SIOSE y depuradas con umbrales de NDVI. Se han ejecutado bancos de pruebas en función de las variables incluidas en el clasificador. Los mejores resultados, en cuanto a porcentaje de acierto y área clasificada,se han obtenido excluyendo la radiación solar de invierno y la banda 1. El proceso se ha realizado por separado para cubiertas naturales y urbanas, con un grado de acierto global superior al 88%, y para cultivos, con un acierto superior al 86%

Environmental and socioeconomic factors of abandonment of rainfed and irrigated crops in northeast Spain

Changes over the last century in the economic model of European countries and the development of the market economy have led to intense shifts in land occupation patterns. Agricultural abandonment is an important consequence of these processes and has modified natural and cultural landscapes, involving side-effects for society. Understanding how environmental and socio-economic factors influence the abandonment process can provide useful insights for managing investments, whether from the public or the private sector. In Spain, the Pyrenees and the Ebro Depression are two differentiated areas in terms of land-use dynamics, particularly in terms of the agricultural model carried out. In this paper we have analyzed the agricultural abandonment in these areas during the 1987-2012 period in relation to several potential explanatory factors. The analysis focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop type and geographical region. Crop covers were classified from four Landsat scenes, and conditions were described by topographic variables, human factors and drought occurrence. Boosted regression trees (BRT) were used to identify the most important variables and to describe the relationships between agricultural abandonment and key factors. Topography derived variables were found to be the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models allowed us to identify other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland

Factors affecting forest dynamics in the Iberian Peninsula from 1987 to 2012 : the role of topography and drought

In southern Europe, climate trends are expected to be characterized by an increase in temperatures and less water availability. Analyzing the role of structural factors and the influence of a changing climate provides insights into the evolution of forest ecosystems in regions with similar environmental conditions. The Mediterranean fringe of the Iberian Peninsula is of particular interest due to its diverse topo climatic conditions and the increase in drought episodes during the last decades. This work studies forest dynamics in large areas of this geographical region by analyzing nine forest transitions. Vegetation covers were classified from three Landsat scenes for the period 1987-2012, and sub-periods 1987-2002 and 2002-2012. Conditions were described by topography derived variables, human factors and drought-occurrence variables. Boosted regression trees were used to identify the most important variables and describe the relationships between the forest dynamics and key factors. Variables such as solar radiation, topographic wetness index and tolerance to drought have been shown to be key factors in forest succession and when comparisons are made between vegetation groups. Main findings: The transition rate to Mediterranean and sub-Mediterranean broadleaf forests has increased during the analyzed period, while the transition rate to coniferous forests has decreased; Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Transitions from shrublands to forest stages are more vulnerable to factors controlling water availability; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met

Depopulation impacts on ecosystem services in Mediterranean rural areas

Despite the exponential increase in human population at global scale, some rural areas have experienced a progressive abandonment over the last decades. Under particular socioecological and policy contexts, changes in demography may promote land-use changes and, consequently, alter ecosystem services (ES) supply. However, most studies on this topic have targeted urban population increase, whereas depopulation has been rarely addressed. Here, we examined how shifts in demographic variables (human population, population density, and number of villages) affect provisioning (water supply, food and biomass production) and regulating (soil retention, water and nutrient regulation) ES in Mediterranean rural areas with contrasting environmental, so-cioeconomic and land-use contexts. When depopulation results in underuse of socio-ecological systems, we ex-pected a decrease of provisioning and an increase of regulating ES, whereas we expected the opposite pattern when it results in land-use intensification. To test this hypothesis, we compared demographic data and ES estimated with Soil and Water Assessment Tool (SWAT) linked to land-use changes between the 1950s and 2000s in three rural areas of Arag ́on (NE Spain). Generalized Additive Mixed Models and Linear Mixed-Effect Models were used to analyze demographic trends, ES changes and the relationship between them. We found severe depopulation (− 42% inhabitants) and associated land-use changes in the three areas, which was particularly evident in isolated mountainous zones (− 63% inhabitants). Depopulation trends significantly affected land use and, consequently, all of the ES evaluated. In mountainous depopulated areas, land abandonment and rewilding resulted in the increase in water regulation (>1000%) and soil retention (>400%). In contrast, agriculture was intensified in more fertile and easy-to-access lowland areas, boosting the food production service (>600%). Accordingly, the interactions among depopulation, crop production and regulating ES should be considered in the management schemes and policies targeting rural areas for a balanced and sustainable supply of ES in the long term

Análisis de factores determinantes de las transiciones forestales y el abandono de cultivos en el ámbito mediterráneo. Un modelo de dinámica de cubiertas del suelo basado en teledetección, SIG y boosted regression trees

El núcleo principal de esta tesis lo componen tres artículos científicos. En el primer artículo se presenta la metodología para la obtención de series temporales de mapas de usos y cubiertas del suelo para grandes superficies de terreno de la franja mediterránea de la Península Ibérica. Para ello se ha implementado un esquema de clasificación de imágenes del satélite Landsat. La información de referencia utilizada para la obtención de áreas de entrenamiento y test ha sido la base de datos SIOSE 2005 (Sistema de Información sobre Ocupación del Suelo de España). El artículo incluye un procedimiento para la obtención de estas áreas en fechas que no disponen de tal información de referencia. Las clasificaciones obtenidas tienen un porcentaje de acierto global superior al 90% y un acierto por categorías temáticas por encima del 85% en la mayoría de los casos. En el segundo artículo se analizan las principales etapas de sucesión y transiciones de vegetación entre las siguientes categorías de cubiertas de vegetación: prados, matorrales, bosques de coníferas, bosques de frondosas perennifolias y bosques de frondosas caducifolias. Los ámbitos de estudio se corresponden con tres escenas Landsat y el periodo de estudio es 1987-2012. Como factores explicativos de estas transiciones se ha utilizado un conjunto de variables de las que destacan las derivadas de la topografía y las variables que cuantifican la recurrencia de periodos secos, obtenidas a partir de un SIG (Sistema de Información Geográfica). Para determinar qué factores son los más importantes y de qué manera influyen en cada etapa de sucesión y transición se ha utilizado el método machine-learning denominado Boosted Regression Trees (BRT). De los resultados obtenidos cabe destacar que las transiciones a frondosas mediterráneas y sub-mediterráneas son más probables en aquellas zonas más afectadas por la repetición de periodos secos, mientras que las transiciones a coníferas son más probables en aquellas zonas con menor ocurrencia de estos eventos, pero que existen importantes interacciones con el contexto topográfico que hay que tener en cuenta. Del análisis se desprende que el decline en la tasa de transición a coníferas y el incremento en la tasa de transición a frondosas se relaciona positivamente con el aumento de periodos secos y que, por tanto, si se cumplen los pronósticos de los modelos climáticos, en algunas zonas podría haber un cambio de especie dominante ante la expansión de las frondosas mediterráneas y sub-mediterráneas. El tercer artículo es un análisis de los factores internos de abandono de, por un lado, cultivos de secano y, por otro, cultivos de regadío también mediante teledetección, SIG y BRT. En este caso son dos ámbitos de estudio (periodo 1987-2012): el Pirineo central español y la cuenca central del Ebro. En este análisis se han incorporado variables que cuantifican el coste de desplazamiento a núcleos urbanos y carreteras, y otras que incluyen información socioeconómica a nivel municipal. De este artículo son también varios los resultados, de los que cabe destacar los siguientes: los limitantes físicos tienen un peso específico muy importante, excepto para los cultivos de regadío en la cuenca central, donde la mayor influencia la tiene acceso a infraestructuras; la actividad agrícola en el Pirineo es más dependiente de mercados internos a nivel local; los cultivos de regadío son más vulnerables a la ocurrencia de sequías; la diversificación económica puede ayudar a mantener la actividad agraria, especialmente en el Pirineo. La probabilidad de abandono no siempre tiene una relación lineal con los factores explicativos, encontrando en algunos casos patrones de respuesta polarizados que reflejan, para un mismo factor, diferentes condiciones que favorecen el abandono.The main core of this thesis consists of three scientific articles. The first article deals with obtaining temporal series of land-use and land-cover maps for large areas of the Mediterranean fringe of the Iberian Peninsula. To do this, a classification scheme of Landsat imagery has been implemented. Training and test areas were extracted from the Land Occupation Information System of Spain 2005 (SIOSE, Sistema de Información sobre Ocupación del Suelo en España). The article includes a procedure for obtaining these areas on dates lacking such kind of reference information. An overall accuracy of over 90% has been obtained for all maps, and accuracy by categories is above 85% in most cases. The second article analyzes the main successional stages and transitions between the following vegetation-cover categories: grasslands, shrublands, coniferous forests, broadleaf evergreen forests and broadleaf deciduous forests. Three areas of Spain were included in this study as different scenarios for model development. Ambits correspond to land-cover classifications of three entire Landsat scene and the study period is 1987-2012. Conditions were described by topography derived variables and drought-occurrence variables, which were obtained through a Geographical Information System (GIS). The machine-learning technique Boosted Regression Trees (BRT) were used to identify the most important variables and describe the relationships between the forest vegetation transitions and key factors. Main findings: Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of Mediterranean and sub-Mediterranean broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met. The third article focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop for two different study areas: the Central Spanish Pyrenees and the Central Ebro Basin. The methodology is also based on remote sensing, GIS and BRT. Variables quantifying the cost distance to urban centers and roads and other variables related to socioeconomic data at a municipal level have been included in this analysis. Topography derived variables are the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models have allowed identifying other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland. The abandonment probability does not always has a linear relationship with the explanatory factors and, in some cases, it shows polarized response patterns that reflect, for a single factor, different contexts prone to be abandoned

Análisis de factores determinantes de las transiciones forestales y el abandono de cultivos en el ámbito mediterráneo. Un modelo de dinámica de cubiertas del suelo basado en teledetección, SIG y boosted regression trees

El núcleo principal de esta tesis lo componen tres artículos científicos. En el primer artículo se presenta la metodología para la obtención de series temporales de mapas de usos y cubiertas del suelo para grandes superficies de terreno de la franja mediterránea de la Península Ibérica. Para ello se ha implementado un esquema de clasificación de imágenes del satélite Landsat. La información de referencia utilizada para la obtención de áreas de entrenamiento y test ha sido la base de datos SIOSE 2005 (Sistema de Información sobre Ocupación del Suelo de España). El artículo incluye un procedimiento para la obtención de estas áreas en fechas que no disponen de tal información de referencia. Las clasificaciones obtenidas tienen un porcentaje de acierto global superior al 90% y un acierto por categorías temáticas por encima del 85% en la mayoría de los casos. En el segundo artículo se analizan las principales etapas de sucesión y transiciones de vegetación entre las siguientes categorías de cubiertas de vegetación: prados, matorrales, bosques de coníferas, bosques de frondosas perennifolias y bosques de frondosas caducifolias. Los ámbitos de estudio se corresponden con tres escenas Landsat y el periodo de estudio es 1987-2012. Como factores explicativos de estas transiciones se ha utilizado un conjunto de variables de las que destacan las derivadas de la topografía y las variables que cuantifican la recurrencia de periodos secos, obtenidas a partir de un SIG (Sistema de Información Geográfica). Para determinar qué factores son los más importantes y de qué manera influyen en cada etapa de sucesión y transición se ha utilizado el método machine-learning denominado Boosted Regression Trees (BRT). De los resultados obtenidos cabe destacar que las transiciones a frondosas mediterráneas y sub-mediterráneas son más probables en aquellas zonas más afectadas por la repetición de periodos secos, mientras que las transiciones a coníferas son más probables en aquellas zonas con menor ocurrencia de estos eventos, pero que existen importantes interacciones con el contexto topográfico que hay que tener en cuenta. Del análisis se desprende que el decline en la tasa de transición a coníferas y el incremento en la tasa de transición a frondosas se relaciona positivamente con el aumento de periodos secos y que, por tanto, si se cumplen los pronósticos de los modelos climáticos, en algunas zonas podría haber un cambio de especie dominante ante la expansión de las frondosas mediterráneas y sub-mediterráneas. El tercer artículo es un análisis de los factores internos de abandono de, por un lado, cultivos de secano y, por otro, cultivos de regadío también mediante teledetección, SIG y BRT. En este caso son dos ámbitos de estudio (periodo 1987-2012): el Pirineo central español y la cuenca central del Ebro. En este análisis se han incorporado variables que cuantifican el coste de desplazamiento a núcleos urbanos y carreteras, y otras que incluyen información socioeconómica a nivel municipal. De este artículo son también varios los resultados, de los que cabe destacar los siguientes: los limitantes físicos tienen un peso específico muy importante, excepto para los cultivos de regadío en la cuenca central, donde la mayor influencia la tiene acceso a infraestructuras; la actividad agrícola en el Pirineo es más dependiente de mercados internos a nivel local; los cultivos de regadío son más vulnerables a la ocurrencia de sequías; la diversificación económica puede ayudar a mantener la actividad agraria, especialmente en el Pirineo. La probabilidad de abandono no siempre tiene una relación lineal con los factores explicativos, encontrando en algunos casos patrones de respuesta polarizados que reflejan, para un mismo factor, diferentes condiciones que favorecen el abandono.The main core of this thesis consists of three scientific articles. The first article deals with obtaining temporal series of land-use and land-cover maps for large areas of the Mediterranean fringe of the Iberian Peninsula. To do this, a classification scheme of Landsat imagery has been implemented. Training and test areas were extracted from the Land Occupation Information System of Spain 2005 (SIOSE, Sistema de Información sobre Ocupación del Suelo en España). The article includes a procedure for obtaining these areas on dates lacking such kind of reference information. An overall accuracy of over 90% has been obtained for all maps, and accuracy by categories is above 85% in most cases. The second article analyzes the main successional stages and transitions between the following vegetation-cover categories: grasslands, shrublands, coniferous forests, broadleaf evergreen forests and broadleaf deciduous forests. Three areas of Spain were included in this study as different scenarios for model development. Ambits correspond to land-cover classifications of three entire Landsat scene and the study period is 1987-2012. Conditions were described by topography derived variables and drought-occurrence variables, which were obtained through a Geographical Information System (GIS). The machine-learning technique Boosted Regression Trees (BRT) were used to identify the most important variables and describe the relationships between the forest vegetation transitions and key factors. Main findings: Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of Mediterranean and sub-Mediterranean broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met. The third article focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop for two different study areas: the Central Spanish Pyrenees and the Central Ebro Basin. The methodology is also based on remote sensing, GIS and BRT. Variables quantifying the cost distance to urban centers and roads and other variables related to socioeconomic data at a municipal level have been included in this analysis. Topography derived variables are the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models have allowed identifying other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland. The abandonment probability does not always has a linear relationship with the explanatory factors and, in some cases, it shows polarized response patterns that reflect, for a single factor, different contexts prone to be abandoned

Cartografía de usos y cubiertas del suelo del sureste de la Península Ibérica a partir de la clasificación de imágenes Landsat en el quinquenio 2000-2004

Se presenta la metodología utilizada en la obtención de la cartografía de usos y cubiertas del suelo para la zona oriental de Andalucía (ámbito de 29.259 km²) en el quinquenio 2000-2004, empleando el clasificador híbrido y utilizando imágenes Landsat junto con las variables auxiliares. Las áreas de entrenamiento se han obtenido de manera semiautomática a partir del SIOSE y depuradas con umbrales de NDVI. Se han ejecutado bancos de pruebas en función de las variables incluidas en el clasificador. Los mejores resultados, en cuanto a porcentaje de acierto y área clasificada,se han obtenido excluyendo la radiación solar de invierno y la banda 1. El proceso se ha realizado por separado para cubiertas naturales y urbanas, con un grado de acierto global superior al 88%, y para cultivos, con un acierto superior al 86%

Assessing vegetation recovery in reclaimed opencast mines of the Teruel coalfield (Spain) using Landsat time series and boosted regression trees

Opencast mining is an activity that caters to many economic sectors; however, it has a large impact on society and the environment. After mining, the major concern is to restore the previous land cover, which was generally a natural vegetation cover. Establishing permanent vegetation cover can restore landscape connectivity and previous ecosystem functions, enhance aesthetic values and prevent off-side effects associated with post-mining landscapes. Opencast mining reclamation deals with these issues with several strategies that aim to develop a vegetation cover after mining activity has stopped. However, not all reclamation actions are effective, and assessing their efficiency by monitoring vegetation development at reclaimed sites is a time-consuming task because it usually involves extensive field work. In this study, we present a semi-automatic approach based on analysing satellite data (Landsat) time series and using a machine learning technique to identify suitable conditions for vegetation development at reclaimed opencast mines. We analysed the Teruel coalfield (Aragón, central-eastern Spain). This area is a representative Mediterranean-Continental region that is of particular interest due the diversity of reclamation actions that have been applied and the increase in drier conditions during the last decades. Conditions were described with topography derived variables, technical reclamation features and drought-occurrence variables as potential explanatory factors. The implemented approach allowed us to identify the main abiotic filters for vegetation of this geographic region: the water availability and soil retention (both controlled by the topographic slope), and the proximity to seed sources. The analysis evidenced the negative influence of drought occurrence on vegetation development, and different responses were found depending on the timescale at which drought is calculated. Our results indicate that the reclamation landform model is the main key factor influencing vegetation development. A model such as the smooth berm-slope increases water availability and controls soil erosion, and hence, improves vegetation development. In addition, we found that further than 500-600 m from the mine, the effect of seed source declines dramatically. Therefore, all these issues should be considered in future reclamation designs in a Mediterranean-Continental environment. Our methodology could be adapted to other geographic regions where spatial environmental data are available.This work was funded by the Aragon Regional Government (Ecological Restoration Group) and co-funded by the European Regional Development Fund 2014-2020 “Building Europe from Aragón”

Análisis de factores determinantes de las transiciones forestales y el abandono de cultivos en el ámbito mediterráneo : un modelo de dinámica de cubiertas del suelo basado en teledetección, SIG y boosted regression trees

Departament i centre responsables de la tesi: Departament de Geografia.Premi Extraordinari de Doctorat concedit pels programes de doctorat de la UAB per curs acadèmic 2017-2018El núcleo principal de esta tesis lo componen tres artículos científicos. En el primer artículo se presenta la metodología para la obtención de series temporales de mapas de usos y cubiertas del suelo para grandes superficies de terreno de la franja mediterránea de la Península Ibérica. Para ello se ha implementado un esquema de clasificación de imágenes del satélite Landsat. La información de referencia utilizada para la obtención de áreas de entrenamiento y test ha sido la base de datos SIOSE 2005 (Sistema de Información sobre Ocupación del Suelo de España). El artículo incluye un procedimiento para la obtención de estas áreas en fechas que no disponen de tal información de referencia. Las clasificaciones obtenidas tienen un porcentaje de acierto global superior al 90% y un acierto por categorías temáticas por encima del 85% en la mayoría de los casos. En el segundo artículo se analizan las principales etapas de sucesión y transiciones de vegetación entre las siguientes categorías de cubiertas de vegetación: prados, matorrales, bosques de coníferas, bosques de frondosas perennifolias y bosques de frondosas caducifolias. Los ámbitos de estudio se corresponden con tres escenas Landsat y el periodo de estudio es 1987-2012. Como factores explicativos de estas transiciones se ha utilizado un conjunto de variables de las que destacan las derivadas de la topografía y las variables que cuantifican la recurrencia de periodos secos, obtenidas a partir de un SIG (Sistema de Información Geográfica). Para determinar qué factores son los más importantes y de qué manera influyen en cada etapa de sucesión y transición se ha utilizado el método machine-learning denominado Boosted Regression Trees (BRT). De los resultados obtenidos cabe destacar que las transiciones a frondosas mediterráneas y sub-mediterráneas son más probables en aquellas zonas más afectadas por la repetición de periodos secos, mientras que las transiciones a coníferas son más probables en aquellas zonas con menor ocurrencia de estos eventos, pero que existen importantes interacciones con el contexto topográfico que hay que tener en cuenta. Del análisis se desprende que el decline en la tasa de transición a coníferas y el incremento en la tasa de transición a frondosas se relaciona positivamente con el aumento de periodos secos y que, por tanto, si se cumplen los pronósticos de los modelos climáticos, en algunas zonas podría haber un cambio de especie dominante ante la expansión de las frondosas mediterráneas y sub-mediterráneas. El tercer artículo es un análisis de los factores internos de abandono de, por un lado, cultivos de secano y, por otro, cultivos de regadío también mediante teledetección, SIG y BRT. En este caso son dos ámbitos de estudio (periodo 1987-2012): el Pirineo central español y la cuenca central del Ebro. En este análisis se han incorporado variables que cuantifican el coste de desplazamiento a núcleos urbanos y carreteras, y otras que incluyen información socioeconómica a nivel municipal. De este artículo son también varios los resultados, de los que cabe destacar los siguientes: los limitantes físicos tienen un peso específico muy importante, excepto para los cultivos de regadío en la cuenca central, donde la mayor influencia la tiene acceso a infraestructuras; la actividad agrícola en el Pirineo es más dependiente de mercados internos a nivel local; los cultivos de regadío son más vulnerables a la ocurrencia de sequías; la diversificación económica puede ayudar a mantener la actividad agraria, especialmente en el Pirineo. La probabilidad de abandono no siempre tiene una relación lineal con los factores explicativos, encontrando en algunos casos patrones de respuesta polarizados que reflejan, para un mismo factor, diferentes condiciones que favorecen el abandono.The main core of this thesis consists of three scientific articles. The first article deals with obtaining temporal series of land-use and land-cover maps for large areas of the Mediterranean fringe of the Iberian Peninsula. To do this, a classification scheme of Landsat imagery has been implemented. Training and test areas were extracted from the Land Occupation Information System of Spain 2005 (SIOSE, Sistema de Información sobre Ocupación del Suelo en España). The article includes a procedure for obtaining these areas on dates lacking such kind of reference information. An overall accuracy of over 90% has been obtained for all maps, and accuracy by categories is above 85% in most cases. The second article analyzes the main successional stages and transitions between the following vegetation-cover categories: grasslands, shrublands, coniferous forests, broadleaf evergreen forests and broadleaf deciduous forests. Three areas of Spain were included in this study as different scenarios for model development. Ambits correspond to land-cover classifications of three entire Landsat scene and the study period is 1987-2012. Conditions were described by topography derived variables and drought-occurrence variables, which were obtained through a Geographical Information System (GIS). The machine-learning technique Boosted Regression Trees (BRT) were used to identify the most important variables and describe the relationships between the forest vegetation transitions and key factors. Main findings: Transitions to Mediterranean and sub-Mediterranean broadleaf forests are positively associated with drought occurrence while transitions to conifers are negatively affected by drought; Important interactions between topography derived variables and drought have been found. The study provides robust evidence that drought occurrence plays an important role in the decline of conifers and the expansion of Mediterranean and sub-Mediterranean broadleaves, which could become the dominant species in many areas of the Mediterranean if climate model forecasts are met. The third article focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop for two different study areas: the Central Spanish Pyrenees and the Central Ebro Basin. The methodology is also based on remote sensing, GIS and BRT. Variables quantifying the cost distance to urban centers and roads and other variables related to socioeconomic data at a municipal level have been included in this analysis. Topography derived variables are the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models have allowed identifying other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland. The abandonment probability does not always has a linear relationship with the explanatory factors and, in some cases, it shows polarized response patterns that reflect, for a single factor, different contexts prone to be abandoned

Environmental and socioeconomic factors of abandonment of rainfed and irrigated crops in northeast Spain

Changes over the last century in the economic model of European countries and the development of the market economy have led to intense shifts in land occupation patterns. Agricultural abandonment is an important consequence of these processes and has modified natural and cultural landscapes, involving side-effects for society. Understanding how environmental and socio-economic factors influence the abandonment process can provide useful insights for managing investments, whether from the public or the private sector. In Spain, the Pyrenees and the Ebro Depression are two differentiated areas in terms of land-use dynamics, particularly in terms of the agricultural model carried out. In this paper we have analyzed the agricultural abandonment in these areas during the 1987-2012 period in relation to several potential explanatory factors. The analysis focuses on the abandonment of rainfed and irrigated herbaceous crops in order to derive specific explanations according to the crop type and geographical region. Crop covers were classified from four Landsat scenes, and conditions were described by topographic variables, human factors and drought occurrence. Boosted regression trees (BRT) were used to identify the most important variables and to describe the relationships between agricultural abandonment and key factors. Topography derived variables were found to be the main determinants, except for irrigated crops in the Ebro Basin, where locational factors play a more important role. BRT models allowed us to identify other significant patterns such as: the vulnerability of irrigated crops to drought; the higher dependence of agricultural activity in the Pyrenees on internal networks; pattern shifts of land abandonment in the analyzed sub-periods, and; evidence of the importance of economic diversification for maintaining cropland