Ecological and socio-economical thresholds of land and plant-community degradation in semi-arid Mediterranean areas of southeastern Spain

Abstract

a b s t r a c tThe climate of semi-arid Mediterranean areas is characterized by highly variable rainfall and seasonal droughts, which favor highly specialized flora, high biodiversity, and the emergence of a large number of endemic species. Such highly specialized complex ecosystems are expected to be more difficult to return to a previous state following perturbation than are more mild ecosystems and lead to dramatic transitions in vegetation. An understanding of the circumstances under which irreversible transition shifts occur is vital in an age of climate change and socio-economic globalization. This will have significant consequences for those highly specialized areas unless management practices, conservation, and preventive measures are increased. Within ecosystems, the interactions between multiple factors acting at multiple temporal and spatial scales, and the inertia of ecological processes, make the consequences of current management practices persist for a long time. To understand the relative importance of the underlying mechanisms that influence the resilience of drylands in southeastern Spain, we reviewed what is known about plantesoil interactions and the spatial distribution of vegetation to detect early warning signs of desertification. We analyzed the role of the self-organizing capacity of vegetation in the formation of vegetation spatial patterns at multiple spatial scales. In addition, we evaluated the importance of threshold indicators as early detectors of transition shifts in dryland ecosystems.

Drought Variability and Land Degradation in Semiarid Regions: Assessment Using Remote Sensing Data and Drought Indices (1982–2011)

“…The large-scale study presented here identifies the main features of vegetation changes in the world's semiarid regions, but cannot provide details of particular processes identified at regional or local scales, some of which are highly complex. These include processes observed in Mediterranean regions, in which the magnitude of the response of the vegetation to drought is very sensitive to differences among sites, seasons, and species, but also to interactions with different environmental factors that determine plant conditions [84,85], and where centuries of significant human pressure have interacted with climate change and drought to produce mosaics of land degradation processes [17,19].…”

“…Nevertheless, some studies have shown that in semiarid regions characterized by soil limitations and intense human pressure, drought intensification as a consequence of warming processes may trigger land degradation processes [17]. These may be irreversible in areas in which edaphic conditions markedly limit vegetation establishment and development [18,19], even with the application of ecological restoration practices [20].…”

Can land degradation drive differences in the C exchange of two similar semiarid ecosystems?

“…This ecosystem type is widespread in the western Mediterranean region: in Cabo de Gata-Níjar Natural Park, a large fraction of agricultural areas that were abandoned over 1957-1994 resulted in espartal ecosystems (Alados et al, 2004(Alados et al, , 2011. The functioning of both experimental sites can be divided into two main periods.…”

“…In this sense, mitigation policies to confront land degradation should be focused on prevention programs since ecosystem restoration does not recover complete ecosystem functionality (Lal, 2001;Moreno-Mateos et al, 2017). Moreover, even after several decades, relict degradation legacies can remain (Alados et al, 2011).…”

Spatial Distribution of Greenhouse Commercial Horticulture in Kenya and the Role of Demographic, Infrastructure and Topo-Edaphic Factors

“…A report by the International Commission on Irrigation and Drainage [71] finds that dam construction significantly increases agricultural production and yield besides enabling farmers to substitute towards water-intensive crops. However, irrigated marginal lands in Spain are largely degrading due to increased extensive agriculture and population expansion is noted in [72]. We identify an urgent need to seek alternative sustainable sources of water, and investigations on water harvesting technologies that can benefit the sector to avoid resource exhaustion.…”