Humans and climate affect ecosystems and their services 1 , which may involve continuous and discontinuous transitions from one stable state to another 2 . Discontinuous transitions are abrupt, irreversible and among the most catastrophic changes of ecosystems identified 1 . For terrestrial ecosystems, it has been hypothesized that vegetation patchiness could be used as a signature of imminent transitions 3,4 . Here, we analyse how vegetation patchiness changes in arid ecosystems with different grazing pressures, using both field data and a modelling approach. In the modelling approach, we extrapolated our analysis to even higher grazing pressures to investigate the vegetation patchiness when desertification is imminent. In three arid Mediterranean ecosystems in Spain, Greece and Morocco, we found that the patch-size distribution of the vegetation follows a power law. Using a stochastic cellular automaton model, we show that local positive interactions among plants can explain such power-law distributions. Furthermore, with increasing grazing pressure, the field data revealed consistent deviations from power laws. Increased grazing pressure leads to similar deviations in the model. When grazing was further increased in the model, we found that these deviations always and only occurred close to transition to desert, independent of the type of transition, and regardless of the vegetation cover. Therefore, we propose that patch-size distributions may be a warning signal for the onset of desertification.It is of the utmost importance to find early warning signals of transitions that can alter ecosystems' services in fundamental ways, causing losses of ecological and economic resources 2,4 . Determining proximity to transitions is especially important for arid ecosystems, which may convert into deserts 2,4,5 . According to the Millennium Ecosystem Assessment, increasing external pressures by human activities or climate change will lead to desertification, affecting the livelihood of more than 25% of the world's population 1 . A mechanism playing a dominant role in the functioning of arid ecosystems is local facilitation among plants [6][7][8][9] . Local facilitation is the biophysical ameliorative effect of sessile organisms, such as plants, on their neighbouring environment. Such local positive interactions induce vegetation patchiness 6,7,10 and determine the response of this patchiness to environmental change 3 .We investigated how the spatial organization of vegetation is influenced by the degree of external stress by combining modelling and field data from three grazed Mediterranean arid ecosystems in Spain, Greece and Morocco. In each of these ecosystems, we collected data on three sites that differed with respect to the livestock grazing pressure (Table 1; Methods). In each of the nine (3 3 3) sites, we analysed the number and the sizes of the vegetation patches (see Methods), and plotted the number of patches, N(S), as a function of their sizes, S. We fitted these patch-size distributions to two different mod...

In this study, we analyze the complexity of plant spatial patterns and diversity along a successional gradient resulting from grazing disturbance in four characteristic ecosystems of the Mediterranean region. Grazing disturbance include not only defoliation by animals, but also associated disturbances as animal trampling, soil compaction, and mineralization by deposition of urine and feces. The results show that woodland and dense matorral are more resistant to species loss than middle dense and scattered matorral, or grassland. Information fractal dimension declined as we moved from a dense to a discontinuous matorral, increasing as we moved to a more scattered matorral and a grassland. In all studied cases, the characteristic species of the natural vegetation declined in frequency and organization with grazing disturbance. Heliophyllous species and others with postrate or rosette twigs increased with grazing pressure, particularly in dense matorral. In the more degraded ecosystem, only species with well-adapted traits, e.g., buried buds or unpalatable qualities showed a clear increase with grazing. Indeed, the homogeneity of species distribution within the plant community declined monotonically with grazing impact. Conversely, the spatial organization of the characteristic plants of each community increased in the better-preserved areas, being also related to the sensitivity of the species to grazing impact. The degree of autocorrelation of plant spatial distribution at the species level and the information fractal dimension at the community level allow us to quantify the degree of degradation of natural communities and to determine the sensitivity of key species to disturbance.

Based on evidence collected in 22 village communities from nine study sites situated in Spain, Italy, Greece, Morocco and China, this study analyses the complex interlinkages between social memory, community resilience and land degradation. Social memory is seen as an important explanation regarding the ability of a local community to manage and cope with land degradation. Emphasis is placed on the importance of three components of social memory—rites, traditions and social learning processes—for shaping community resilience in coping with land degradation processes. The study argues that although there are subtle differences between the 22 village communities, the loss of social memory and learning pathways associated with managing land degradation is emerging as a critical factor constraining stakeholders from effectively responding to land degradation issues. Copyright © 2016 John Wiley & Sons, Ltd.

The objective of this chapter is to present findings from our experimental work, as well as from other research institutes, related to the composition and quality of goat meat, particularly the lipid profile, with emphasis on dietary factors and feeding programmes. This topic is of current concern as the fatty acid (FA) composition of ruminant meats and fats contains essential FAs for health, conjugated linoleic acids (CLAs), which reduce the risks of cardiovascular diseases and cancers. It also plays a role in the organoleptic, nutritional and dietetic quality of meat. The FA compositions of kid and lamb meats are not very different. However, kid meat was observed to be a little richer in polyunsaturated fatty acids (PUFAs), ω-3 fatty acids and CLAs, although it was not clear whether this was due to a direct effect of species. In kids, as in other ruminants, muscle lipids are more unsaturated, richer in PUFAs and lower in saturated fatty acids (SFAs) than subcutaneous adipose tissues and especially internal fats. However, the subcutaneous fats are more sensitive to factors modifying their FA composition. Experimental information on the effect of factors modifying the lipid composition of meats and fats in kids is less available than in lambs and steers. The dietary factors and type of feeding system are the main factors, but it is difficult to evaluate their direct effects because of the influence of other factors such as genotype, sex and stage of growth. During the milk-feeding period, feeding systems based on dam grazing or supplementations with linseeds, fish oil or PUFA mixtures can increase the proportions of desirable FAs such as ω-3, PUFAs and CLAs, and decrease C18:1 and C16:0 fatty acids and SFAs in dams' milk and, to a lesser extent, in meat lipids and fats of suckling kids. During post-weaning periods, similar feeding systems with kids can have similar effects on meat and fats, although the results are limited and heterogeneous. Future progress in the commercialization of kid meat may occur but only if its quality, particularly dietetic aspects, is markedly good. Therefore, the dietetic quality of lipids present in meat or in consumed fats must be improved. Kid rearing systems such as under Argan tree forests in Morocco have been shown to reduce the proportion of fats in meat, increase the proportion of desirable FAs such as CLAs and the cholesterol content in meat, and decrease the ω-6:ω-3 ratio to about 5. Such findings allow optimism for the future in the production and consumption of goat meat.

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