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The Skagit River valley in northern Washington and southern British Columbia contains long interconnected valleys, barbed tributaries, underfit streams, and low-elevation mid-valley divides. Quantitative measures of connectivity between valleys draining through breached mountain divides, aerial photographs, and a field-verified, process-form model were used to assess the impact of continental glaciation on the drainage pattern and geomorphology of the watershed. Structural control on drainage patterns and intense, repeated continental glaciation rendered the Skagit an extremely interconnected valley, with meltwater routes opening it to the Fraser and Okanagan watersheds. Divide elimination by drainage of large proglacial lakes led to several hundred meters of erosion at 10 breached divides. Other geomorphic effects of recurrent continental glaciation include the bisection of a major mountain valley, divide migration of as much as 50 km, erosion of canyons 15–30 km downstream of breached divides, and deposition of exceptionally large alluvial fans at canyon mouths. Drainage patterns established in the Tertiary were reorganized to accommodate southern drainage of glacial meltwater trapped in mountain valleys at the southern margin of the Cordilleran Ice Sheet. The Skagit basin is now a regional focus for drainage to Puget Sound from the northernmost North Cascades and parts of southern interior British Columbia. The key to establishing this system was the elimination of a regional divide in what is now Skagit Gorge, which resulted in the capture of the upper Skagit valley by the lower Skagit River. Patterns of drainage modification caused by continental glaciation in the Skagit basin are similar to those in other mountain areas. The Skagit's interconnected valleys are similar to the great through-valleys of Scotland, transmountain valleys of British Columbia, and ice portals of Scandinavia.

The effect of livestock grazing on the under-story vegetation in a Mediterranean Pinus nigra forest pasture in the Pyrenees was studied during 6 years, by comparing changes in herbaceous and shrub vegetation under cattle grazing conditions or in absence of livestock. Cattle grazed the pasture each year at a moderate stocking rate of 0.2 LU/ha, for 3 months in spring and 3 months in the autumn. Four 10 m × 10 m exclosures were set up in different locations in the range. Each year, at the end of the grazing season, herbage height and biomass and shrub number, volume and biomass were measured inside and outside the exclosures. Herbage quality was measured at the end of the study. After 6 years, herbage biomass was much greater inside the exclosures (1730 kg DM/ha versus 679 kg DM/ha, p

The research was carried out in the “Sierra y Canones de Guara” Natural Park, a protected mountain area located in the Central Pyrenees (Huesca, Spain). In this territory, a notorious recession of agricultural activities has been observed in recent decades, which has originated changes in the type and intensity of land utilization and, simultaneously, led to environmental and landscape degradation. The main goal of this research was to analyse what characteristics of the current sheep farming systems could explain different patterns of utilization of the grazing resources. Information was obtained through direct interviews with all sheep farmers that used the grazing resources of the Park in 2000 (n = 53). Specific information on grazing management (grazing areas, grazing periods, number and type of grazing animals) was collected together with data on family characteristics, labour, flock management, land use, continuity, recent changes in farming and farmers opinions. Principal Components Analysis was used to examine relationships among original variables. Farming systems were then characterized in four homogeneous groups using Cluster Analysis. Finally, a Logistic Regression allowed determining relationships between the level of intensification of management and several social and technical features. Intensification of farm management was linked to the type and intensity of land utilization: the higher the intensification of the reproduction system the shorter the grazing period and the lower number of grazing animals. Besides, chances of continuity were critical in some groups of farms, especially in some of the most extensive ones, while many farms with good chances of permanence showed more intensive management strategies but lower utilization of grazing resources. In this type of agro-ecosystems, rural development policies with conservation purposes should focus on farming systems with more environmentally desirable management strategies, and consequently enhance their chances of continuity.

The ‘Sierra de Guara’ Natural Park (81,491 ha, Huesca, Spain) is a protected Mediterranean mountain area dominated by shrub and forest pastures. Traditional agriculture, mainly extensive grazing systems, has decreased in the last decades; concurrently, invasion of shrub vegetation, landscape changes and higher risk of forest fires have been observed. A study, which started in 2000, was carried out with two broad objectives: at the farm level, to analyse the farming systems and evaluate management strategies; at the regional level, to give useful information to conservation authorities for better decision-making. An integrated approach with different spatial scales and methods of analysis was used. First, a survey covering all farms that utilized the Park was carried out and livestock farming systems were characterized in terms of grazing management, technical and socio-economic factors. Second, six representative areas were selected to evaluate, depending on livestock utilization, grass and shrub vegetation dynamics (biomass, green/dead ratio). Third, vegetation and livestock data were analysed using a Geographic Information System to identify constraining factors and areas of intervention. Key imbalances were identified that can threaten the sustainability of the Park: low continuity of farming families; intensification of the management system; degradation of grazing resources; and concentration of grazing areas. A number of management recommendations are raised.

Understanding the complex interactions between livestock and the environment is key in the current global context, although the wide diversity of these interactions in the different production systems needs a local approach. In ruminant production systems, ongoing research is focused on quantification of both negative and positive environmental impacts, developing adaptation and mitigation strategies to reduce the former, through increased efficiency and reduced inputs and emissions, and enhancing the later. In extensive conditions, both aims can be achieved by adapting livestock management to the provision of natural foraging resources throughout the year, yet fulfilling other societal demands like the provision of market-oriented products. In this framework, a series of studies will be presented concerning (1) the response of natural vegetation to extensive livestock grazing in different conditions; how farming systems can adapt to seasonal, spatial and nutritional quality of feed resources; and the effect of grazing on animal performance and product quality.

The management of natural resources in Protected Natural Areas needs to bring together the interests of many different stakeholders. For this purpose, multi-agent simulation systems (MAS) can be used to develop virtual environments in which the consequences of different management strategies on the ecosystem can be tested. In this context, a prototype of a MAS model was built for Sierra de Guara Natural Park (Spain, 80,739 ha), a typical Mediterranean mountain area where agricultural abandonment has occurred progressively in the last decades. In order to determine the evolution of vegetation types in time and space, information on current distribution of vegetation cover was used to set up the initial state of the model, which could change due to a ‘densification’ function defined from previous studies and that was dependent on management. According to the theory of states and transitions in vegetation dynamics, once a threshold was reached, a particular vegetation unit could change to a denser vegetation type. Three different management scenarios were evaluated: abandonment of agriculture and livestock production, with occurrence or absence of natural fires, and continuity of current farming practices (on 53% of the total Park area). Simulations were carried out until an equilibrium state was reached (60 to 80 years depending on scenarios). Agricultural abandonment led to a rapid densification of vegetation, with lower diversity at the equilibrium situation (higher proportion of forest cover). This trend was more irregular when natural fire was included in the model, and more grassland and shrub pastures were observed at equilibrium. Current farming practices still led to some changes in vegetation, but were mostly concentrated in non-used areas; vegetation cover diversity at equilibrium was higher in this scenario. The utility of this approach as a decision support tool, even at its preliminary stage, was demonstrated.