LEDD issues in grazing land: general

Editor's note 14Jun2012: Text source D211, section 3.1.

Although LEDD issues are primarily environmental problems, they generate associated socio-economic consequences. The LEDD issues in grazing land that are examined in this deliverable are presented in Table 1 below. The Table distinguishes between the environmental and the socio-economic aspects of these issues which are manifested at all spatial levels (global, national, regional, local).

Table 1. LEDD issues in grazing land

Source: LEDDRA Study Site Application Plan 2011

Changes in the human population over the next few decades will be key in determining the loss of biodiversity caused by pushing animal and plant populations past critical thresholds of tolerance and renewal (Cincotta et al. 2000). The Mediterranean basin is identified as a biodiversity hotspot, rich in endemic species and particularly threatened by socio-economic factors. Cincotta et al. (2000) estimated that the human population growth rate will be the main leading force reducing biodiversity in the future. Habitat conservation is affected by demands for housing, arable land, freshwater, manufacturing, as well as by land degradation and climate change, all of which threaten ecosystem functioning and increase the risk of further species extinctions. Rangeland ecosystems have been concentrated in marginal areas, where grassland production is relatively low, and with strong seasonal and annual variability. Landscape conservation in this situation is complex and influenced by interactions of grazing pressure, rainfall, soil conditions and grazing history (Milchunas and Lauenroth 1993; Turner 1999).

Land degradation and desertification in arid and semi-arid  areas is a critical problem affecting 19 percent of the world’s land surface, according to UNEP (1978).  Dryland areas account for 45 percent of land surface, and rangelands support 50 percent of the world’s livestock (Puigdefábregas 1998). Drylands are primarily affected by rainfall variability and human disturbances, rather than by plant or animal interactions (Ellis et al. 1993). Overgrazing and fires, together with episodic drought events, result in vegetation transition triggers. The end result is land and ecosystem degradation and desertification due to positive feedback caused by overexploitation.

In alpine and subalpine plant communities livestock reduction in grazing lands might have a significant impact on plants by altering facilitative-competitive interactions (Callaway et al. 2002), influencing population dynamics, and biodiversity. In addition, climate change is expected to have significant effects on alpine and subalpine vegetation (Thuiller et al. 2005). Coupled with rising temperatures, reduction of precipitation, land use change and globalisation processes (i.e. abandonment of grazing and changes in grazing practices) these processes are expected to have cascading effects on ecosystem processes, accelerating the invasion of grasslands by highly competitive woody species, and threatening ecosystem functions and services.

Grazing can disrupt the spatial structure of plant communities and alter dominance hierarchies (Roques et al. 2001; Rebollo et al. 2002; Alados et al. 2003), which affects the spatial distribution of biodiversity and has significant implications for the functioning of ecosystems. In recent years, changes in land use and other human activities have resulted in a decrease in species richness world-wide (Hooper et al. 2005). Species richness is seen as an insurance against a decline in ecosystem services, such as the prevention of soil erosion and maintenance of hydrological cycles (Hooper et al. 2005). Commonly, biological diversity is associated with the efficient use of resources and ecosystem resilience (Tilman and Kareiva 1996; Chapin et al. 1997; Walker et al. 1999); however, high diversity is not always associated with ecosystem performance and resilience. Grazing can foster invasions by weeds and lead to a reduction in the richness of native plants (Prober and Thiele 1995; Hobbs 2001).

Understanding how grazing influences the spatial distribution of species can depend on the scale of analysis (Adler et al. 2001; Spiegelberger et al. 2006). At lower scales, plant interactions determine species distribution and grazing will increase the number of microhabitats through spatially heterogeneous defoliation, trampling, wallowing and faecal deposition (WallisDeVries et al. 1998). At larger scales, Spiegelberger (2006) observed that grazing management has an important effect on species distribution, leading to larger homogenization of intensively managed grasslands than in traditional managed grasslands. Consequently, the effect of land use on plant species richness in mountain grasslands is scale-dependent. Until recently, most of the research has focused on phenomena at a local scale, e.g., resource availability, productivity, biotic interactions, and disturbance (Huston 1979; Tilman 1988; Huston 1994; Grace 1999), and the effect of grazing on the spatial distribution of diversity at multiple spatial scales has not been investigated. Today, however, there is considerable interest in the effects of regional phenomena (Ricklefs 1987; Huston 1999), such as species pools (Zobel 1997), on community composition and biodiversity.

Europe has adopted numerous policy initiatives in this area, related both to its own strategy (European Community Biodiversity Strategy and its Action Plans (drafted in compliance with UNCED), the Sixth Community Environment Action programme, Habitats Directive), and to global strategies (UN Convention on Biological Diversity, UN Framework Convention on Climate Change, Pan-European Biological and Landscape Diversity Strategy, the Millennium Assessment). One of the societal objectives that both transcends and integrates all of these is the Gothenburg target; to halt further biodiversity loss by 2010(M.E.A. 2005). This objective is particularly relevant when studying the effects of anthropogenic disturbance in natural ecosystems, particularly in Europe where the landscape to be conserved depends on traditional agri-pastoral land use in mountain areas with low mechanisation. Much of these areas are under priority conservation for European measures (EEA 2004). The EU has played a leading role in the development and implementation of climate change mitigation policies (e.g. support of the United Nations Framework Convention on Climate Change (UNFCCC) and the Kyoto Protocol). The EU is also an important signatory of the Convention on Biological Diversity, with responsibilities to implement policy in new member states, as well as to encourage its application in developing nations. For the coordination of the European policy on Climate Change the European Union implemented the European Climate Change Program in 2000 (updated 2006).

These objectives involve new challenges to environmental management because current management of natural resources (biodiversity, agriculture and forestry, water for power generation) is not considering changing boundary conditions, and especially changing climate and associated impacts on land use and other environmental drivers (EEA 2004). For example, current biodiversity conservation networks in Europe, including Natura 2000, are not adequate to sustain biodiversity protection in the face of climate change. The Intergovernmental Panel on Climate Change (IPCC) assessments and the Millennium Ecosystem Assessment, among others, have shown this assumption to be no longer tenable (IPCC 2007).

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