The Role of Recent (1985–2014) Patterns of Land Abandonment and Environmental Factors in the Establishment and Growth of Secondary Forests in the Iberian Peninsula

Abstract

Farmland abandonment has been a widespread land-use change in the Iberian Peninsula since the second half of the 20th century, leading to the establishment of secondary forests across the region. In this study, we aimed to address changes in the recent (1985–2014) emergence patterns of these forests and examine how environmental factors affected their growth by considering differences in leaf-habit types. We used a combination of Landsat-derived land-cover maps and aboveground biomass (AGB) maps from the European Space Agency to assess the secondary forest establishment and growth, respectively, in the study region. We also obtained a set of topographic, climatic and landscape variables from diverse GIS layers and used them for determining changes over time in the environmental drivers of forest establishment and AGB using general linear models. The results highlight that secondary forest cover was still increasing in the Iberian Peninsula at a rate above the European average. Yet, they also indicate a directional change in the emergence of secondary forests towards lower and less steep regions with higher water availability (mean rainfall and SPEI) and less forest cover but are subjected to greater drought events. In addition, these environmental factors differentially affect the growth of forests with different leaf-habit types: i.e., needleleaf secondary forests being less favoured by high temperature and precipitation, and broadleaf deciduous forests being most negatively affected by drought. Finally, these spatial patterns of forest emergence and the contrasting responses of forest leaf-habits to environmental factors explained the major development of broadleaf evergreen compared to broadleaf deciduous forests and, especially, needleleaf secondary forests. These results will improve the knowledge of forest dynamics that have occurred in the Iberian Peninsula in recent decades and provide an essential tool for understanding the potential effects of climate warming on secondary forest growth.

Driving Forces of Forest Expansion Dynamics across the Iberian Peninsula (1987–2017): A Spatio-Temporal Transect

“…Our results showed that the main topoclimatic determinant of crop abandonment to new BDF was precipitation, mainly in the case of rainfed crops with an increasing positive tendency. In some studies, this variable was initially removed due to the correlation with other drivers [30,64], whereas in others, it appeared as the main one [21,66]. Other topoclimatic drivers obtained from our analysis were temperature and slope, with a negative (except for the Thermomediterranean region) and a positive gradient, respectively.…”

“…Studies quite often evaluate the drivers involved in LC dynamics focusing on a specific issue or complex phenomenon to be analyzed, unifying several categories from LC maps into a unique "label", i.e., forest regrowth, deforestation, and cropland abandonment, which constitutes the phenomenon as a target for analysis in research works [19,21,30,33]. The study also benefited from investigating NF appearance, disaggregated into three forest types, focusing on six main source categories for the sake of understanding the specific drivers involved.…”

“…Recently, Gelabert et al [20] estimated an overall area proportion of 66% affected by woody encroachment on former pastures and croplands in the Pyrenees. Despite indicating a progressive increase in forest cover over the past century, official data do not provide enough robust information to ascertain the spatial pattern of this increase and its links to other processes and to the potential drivers, although this situation is changing [19,21]. More detail about the spatial patterns of the driving forces associated with the main sources of new forests is fundamental for landscape management and planning.…”

Tendencias recientes del NDVI en Andalucía: los límites del reverdecimiento

“…factores que condicionan la disponibilidad de agua y determinan diferentes trayectorias o transiciones forestales, en las que unas comunidades forestales son beneficiadas frente a otras que resultan perjudicadas (Delgado-Artés et al, 2022;José Vidal-Macua et al, 2017). La matorralización y revegetación con bosques secundarios evidencia una adaptación de las comunidades mejor adaptadas a la sequía (Palmero-iniesta et al, 2021), parámetro que está experimentando una tendencia positiva si consideramos los incrementos de temperatura y evapotranspiración en el sur de la península ibérica (Páscoa et al, 2021;Tomas-Burguera et al, 2021). En este nuevo contexto socioecológico y ambiental, el impacto de los incendios forestales está cobrando una mayor importancia sobre la dinámica de la vegetación en la región mediterránea (Resco de Dios et al, 2006).…”

Assessing Wildfire Exposure to Communities and Protected Areas in Portugal

“…Besides the recent extreme weather events, the rapid fuels buildup since the 1960s is also a primary driver behind catastrophic wildfires in Portugal and the European Mediterranean areas. The highly fragmented cultural landscapes evolved into a dense forest continuum that resulted from rural population exodus, extensive afforestation efforts to grow commercial softwood, farmland abandonment, and livestock confinement [12][13][14][15][16]. The suburban sprawl around city centers expanded into the surrounding agricultural plains [17,18], and rapid-growing conifer species and shrublands invaded abandoned olive groves, vineyards, small arable land parcels, and grasslands [19].…”