Drylands are one of the most diverse yet highly vulnerable social–ecological systems on Earth. Water scarcity has contributed to high levels of heterogeneity, variability and unpredictability, which together have shaped the long coadaptative process of coupling humans and nature. Land degradation and desertification in drylands are some of the largest and most far-reaching global environmental and social change problems, and thus are a daunting challenge for science and society. In this study, we merged the Drylands Development Paradigm, Holling's adaptive cycle metaphor and resilience theory to assess the challenges and opportunities for livelihood development in the Amapola dryland social–ecological system (DSES), a small isolated village in the semi-arid region of Mexico. After 450 years of local social–ecological evolution, external drivers (neoliberal policies, change in land reform legislation) have become the most dominant force in livelihood development, at the cost of loss of natural and cultural capital and an increasingly dysfunctional landscape. Local DSESs have become increasingly coupled to dynamic larger-scale drivers. Hence, cross-scale connectedness feeds back on and transforms local self-sustaining subsistence farming conditions, causing loss of livelihood resilience and diversification in a globally changing world. Effective efforts to combat desertification and improve livelihood security in DSESs need to consider their cyclical rhythms. Hence, we advocate novel dryland stewardship strategies, which foster adaptive capacity, and continuous evaluation and social learning at all levels. Finally, we call for an effective, flexible and viable policy framework that enhances local biotic and cultural diversity of drylands to transform global drylands into a resilient biome in the context of global environmental and social change.

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This investigation was undertaken to determine the concentrations of lead in bird blood samples from a mining region in central Mexico and to compare concentrations among several different feeding guilds. The study took place in the Mexican state of San Luis Potosi in a region known as "Villa de la Paz." This is one of the most intensely exploited mining regions in central Mexico and has been actively mined for over four centuries. Lead concentrations from bird blood samples taken from four polluted sites were significantly higher than those from a control, unpolluted site (F = 6.3, P < 0.0002). Similarly, mean blood lead concentrations in birds from a highly polluted site were higher than those from a site that has intermediate pollution levels (P < 0.05). In addition, samples from insectivorous birds had significantly lower lead concentrations compared to granivores, frugivores-insectivores, and omnivores (F = 4.86, P = 0.004), and a large proportion of all individuals had blood lead concentrations indicative of low, sub-lethal toxic effects. Finally, in two polluted sites, remarkably small numbers of insectivore-frugivores, and granivores were trapped, and in one polluted site a large number of insectivores was trapped (X(2) = 29.9, P = 0.03), and no differences in proportions of migrants and non-migrants were found among sampling sites (X(2) = 0.6, P = 0.96). To date, it has not been determined to what extent constant exposure to these levels of pollution can influence health at the individual level, lifespan, and, therefore, population demography of birds from this region.

The current study aimed at quantifying arsenic and lead in feathers from three passerine species that are residents from areas exposed to mining activities (Toxostoma curvirostre, Campylorhynchus brunneicapillus, and Melozone fusca). Lead and As contents in bird feathers and in superficial soil samples were measured with AAS. Levels of these metals were compared between sites exposed and unexposed to mining. Possible correlations of As and Pb between superficial soil and bird feathers were also investigated. Soil metal concentrations were significantly higher near mining sites, and metal concentrations in bird feathers showed a behavior similar to those recorded for soil samples. Individual birds from polluted sites had higher mean feather metal concentrations in comparison with non-polluted sites; no differences in metal concentrations were recorded among bird species. This work constitutes a basis for monitoring contaminants, and for future toxicological studies attempting to understand the impact that some mining activities may have on bird populations.