Shifts in plant species and biome distribution in response to warming have been described in past climate changes. However, reported evidence of such shifts under current climate change is still scarce. By comparing current and 1945 vegetation distribution in the Montseny mountains (Catalonia, NE Spain), we report here a progressive replacement of cold-temperate ecosystems by Mediterranean ecosystems. Beech (Fagus sylvatica) forest has shifted altitudinally upwards by ca. 70 m at the highest altitudes (1600±1700 m). Both the beech forests and the heather (Calluna vulgaris) heathlands are being replaced by holm oak (Quercus ilex) forest at medium altitudes (800±1400 m). This beech replacement has been observed to occur through a progressive isolation and degradation of beech stands. In`isolated' (small and surrounded by holm oaks) beech stands, beech trees are 30% more defoliated, beech recruitment is 41% lower, and holm oak recruitment is three times higher than in`continental' (large and continuous) beech stands. The progressively warmer conditions, complemented by the land use changes (mainly the cessation of traditional land management) are the apparent causes, providing a paradigmatic example of global change affecting distributions of plant species and biomes.

Altitudinal upward shifts of species’ ranges have occurred across a wide range of taxonomic groups and geographical locations during the twentieth century in response to current climate warming. However, actual data of plant species’ altitudinal shifts are still scarce and not always clear. Here we provide a more detailed investigation of a previously reported European beech Fagus sylvatica forest altitudinal shift in the Montseny Mountains (Catalonia, NE Spain) now based on field photographic survey and on the population age structure and the recruitment patterns in the high Fagus limit (HFL), the central forest area (CFA) and the low Fagus limit (LFL). Monitoring of the lowest altitudinal range shows that beech forest is being progressively replaced by Mediterranean holm oak forest. Holm oaks are characterized by recruitment rates more than three times higher than those of beech in the LFL in the last decades. The percentage of young individuals in the LFL is only half that in the HFL and CFA. In the highest altitudinal range, present day and early 20th century photographs show that the HFL has gained density and has shifted altitudinally upwards, advancing with establishment of new, vigorous outpost trees (13 individuals per each 100 m of tree‐line). They are mostly (89%) younger than 35 yr old and mostly (97%) located up to 70 m (with a few up to 105 m) ground surface distance above the current tree line (36–51 m altitude) at the highest altitudes (1600–1700 m). The beech forest upward shift is a likely consequence of warming, but land‐use practice changes (cessation of burning by shepherds) have made it possible. These changes in vegetation distribution and population structure constitute a new indication of the complex global change effects on life in mountain ecosystems.

ABSTRACT. The governance of ecosystem services (ES) has been predominantly thought of in terms of market or state-based instruments. Comparatively, collective action mechanisms have rarely been considered. This paper addresses this gap by proposing a conceptual framework that brings together ES, social interdependencies, and collective action thinking. We use an ES conceptual lens to highlight social interdependencies among people so as to reflect on existing or potential collective actions among them. This framework can also contribute to increasing people's awareness of their mutual interdependencies and thereby fostering, framing, or enriching collective action, in ways that take into account the diversity and complexity of ecological processes underlying human activities. Our approach can contribute in particular to agroecological transitions that require landscape level innovations and coordination mechanisms among land users and managers. The framework distinguishes three types of social interdependencies: (i) between ES beneficiaries and ES providers, (ii) among beneficiaries, and (iii) among providers. These social interdependencies are in turn analyzed according to four main dimensions that are critical for collective action: (i) cognitive framing of interdependencies, (ii) levels of organization, (iii) formal and informal institutions, and (iv) power relations. Finally, we propose a strategy to turn this framework into action in contexts of participatory action research, a strategy grounded on a number of methodological principles and tools that convey complexity and increase people's awareness of interdependencies in agrarian social-ecological systems.

ABSTRACT. The effects of land abandonment on biodiversity have received considerable attention by scholars, but results are far from conclusive. Different cultural traditions of scientists seem to underlie the contrasting ways in which land abandonment is understood. Although the forest transition (FT) framework considers land abandonment as an opportunity for biodiversity conservation, European landscape ecologists characterize it as a threat. We use insights from both traditions to analyze the effects of land abandonment on landscape and biodiversity in a mountain area of metropolitan Barcelona. We do so through an in-depth historical case study covering a period of 160 years. A set of landscape metrics was applied to land-cover maps derived from cadastral cartography to characterize the landscape ecological changes brought about by land abandonment. Cadastral data on land uses were used to understand how landscape ecological changes could be explained by changing socioeconomic activities. Information on past landmanagement practices from semistructured interviews was used to shed light on how peasants shaped the capacity of landscape to host biodiversity. Our results point to a remarkable landscape deterioration along with the disappearance of the peasant land-use mosaics and the ensuing forest expansion. By using insights from landscape ecology in a historically informed manner, we (1) question the alleged relationship between land abandonment and ecosystem recovery; (2) show that the assumed restorative character of the FT is based on the underestimation of the ecological importance of nonforest habitats; and (3) point at a remarkable trade-off between FT and biodiversity in the Mediterranean. Finally, the case study also serves to illustrate some of the strengths and challenges of using historical approaches to land abandonment.

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