LEDD issues

LEDD issues in grazing land: general

2012-06-14T07:21:19+00:00

Authors: Conceptión Alados, Erea Paz, Frederico Filliat, Maite Gartzia

{xtypo_alert}Editor's note 14Jun2012: Text source D211, section 3.1.{/xtypo_alert}

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

Type of Issue	LEDD Issue
Environmental issues	Soil erosion Soil organic matter redistribution Loss of biodiversity Ecosystem fragmentation Soil compaction Soil crusting Flooding Soil contamination Land desertification Land and ecosystem fragmentation Increased incidence of fires Productivity decline and decrease in carrying capacity
Socio-economic issues	Rural depopulation Land use change Loss of traditional knowledge Poverty Unemployment Loss of social cohesion Land abandonment Decline in property values Farm and land fragmentation Conflict among pastoralists

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).

LEDD issues in grazing land: Crete and Asterousia

2012-06-14T07:48:45+00:00

Author: Constantinos Kosmas

{xtypo_alert}Editor's note 14Jun2012: Text source D211, section 3.1.2{/xtypo_alert}

Grazing land covers extensive areas of Greece. Animal husbandry contributes significantly to the economy of the country. In addition, grazing land is faced with many problems of land degradation and land productivity decline. Irrational and uncontrolled land clearing, forest fires and overgrazing are the main causes of land degradation and desertification of grazing land (Greek Action Plan for Combating Desertification 2001). Removal of natural vegetation, especially in degraded land, favours accelerated soil erosion leading to land desertification. The most important issues related to LEDD in grazing land in Greece and in Crete are the following: (a) low land productivity, (b) soil erosion, and (c) land desertification.

Low land productivity

In Greece, long periods of grazing combined with adverse climatic, soil and topographic conditions, in association with or without wildfires, have led to soil degradation and negative effects on land productivity and conservation of natural ecosystems. This has resulted in decisive measures to exclude livestock from some areas, particularly those characterized by specific environmental characteristics. However, it has to be noted that no-grazing or under-grazing may also cause adverse effects, such as the disappearance of grazing-prone species, or the accumulation of flammable biomass, which is one cause of recurring wildfires (Seligman and Perevolotsky 1992).

The long history of livestock husbandry in Greece has resulted in the adaptation of the flora to grazing pressure (Rackham and Moody 1996), and there is growing evidence of plant community response to grazing that suggests that grazing at moderate or even high intensities can in certain areas be a necessary component of a conservation strategy (Papanastasis 2008). It may locally be considered as a solution for the protection of abandoned rural areas and for a reduction of livestock production costs in a highly competitive European and international market (Papanastasis and Peter 1998). Low land productivity has a significant impact on farm income and grazing land management. When land productivity is low, farmers need large areas of additional land to produce animal feed or must buy feed from other areas, increasing the cost of production. Furthermore, under low land productivity conditions, rangeland is usually overgrazed leading to accelerated soil erosion rates, land degradation and desertification.

Soil erosion

Pastures in Greece have been significantly affected by soil erosion processes for many years. Greece is a rugged, mountainous country with high variation in altitude. Due to its predominantly steep terrain and adverse climatic and bio-climatic conditions, the country is facing considerable soil erosion problems. Natural environmental factors, adverse as they are, would not have caused the current extent of land degradation without the addition of human pressures. Deforestation has taken place to provide fuel, timber for house building, ship construction, and other purposes over many centuries. Shepherds used fire to eradicate woody vegetation and encourage the growth of grass, which has subsequently been overgrazed.

Extensively eroded areas in grazing land are confined to rock formations primarily of Mesozoic limestone and secondarily of acid igneous and metamorphic rocks. Soils formed on limestone usually have moderately fine to fine texture. Drier microclimatic conditions prevail in these areas, reducing the potential for plant growth, and the soils remain bare for long periods, favouring overland flow and erosion. The soils on these areas are very shallow or the parent rock is exposed at the surface (Yassoglou and Kosmas 2000).

Soil erosion experiments conducted in Mediterranean shrublands which are used mainly for grazing have shown that soil erosion rates depend on annual rainfall (Kosmas et al. 1996), vegetation cover and livestock density. Vegetative cover is highly dependent on annual rainfall and the time of year. Areas located in the western part of the country have higher annual precipitation (650-1150 mm) and usually higher vegetation cover if the soil is relatively deep. In contrast, the eastern and southern parts of the country receive lower precipitation (380-650 mm) and usually have a poorer vegetation cover. Erosion rates measured on Zakynthos range from 0.2 to 1.6 t km-² yr-¹, while higher erosion rates are expected in the eastern part of the country (Kosmas et al. 1996). Soil depth and type of parent material affect vegetation cover and erosion rates. Long-term studies conducted in various shrublands or abandoned lands of Greece have shown that the following two classes of soil depth may be distinguished for land protection (Kosmas et al. 2000):

A critical soil depth (25-30 cm), below which the recovery of the natural vegetation is very low, and the erosion processes may be very active resulting in accelerated soil erosion rates;
A crucial soil depth (4-10 cm) under which perennial vegetation cannot be sustained, the soil is rapidly removed by wind or water erosion, so that degradation of the land is an irreversible process.

Many authors have demonstrated that in a wide range of environments both runoff and sediment loss decrease exponentially as the percentage of vegetation cover increases (Lee and Skogerboe 1985; Francis and Thornes 1990). Vegetation cover of 45-50 percent greatly reduces surface water runoff (Kosmas et al. 1996). Therefore, land management of pastures for reducing soil erosion in highly degraded soils is crucial for combating land degradation and desertification.

Soil erosion in grazing land in Crete is the most important LEDD issue. The application of the PESERA model in grazing land in western Crete has shown various rates of soil erosion depending on soil, vegetation, topographic and vegetation characteristics (DESIRE contract No: 037046). The following soil erosion classes: 10-20 t ha-¹ yr-¹, 20-50 t ha-¹ yr-¹ have been estimated under very steep slopes (slope gradient >35 percent), shallow soil depths (less than 30 cm), and plant cover less than 55 percent. Of course, there are areas highly degraded with extensive rock outcrops, mainly limestone, in which soil erosion is hardly active any more.

Land desertification

Desertification, as defined by the UNCCD, has affected large areas of pastureland in Greece. The vulnerability of the land to severe degradation, and as a consequence to desertification is attributed to unsustainable land management practices combined with unfavourable physical environmental characteristics.

The following main factors are considered as the most important affecting land degradation and desertification of pastures in Greece:

Large moisture deficits, temporal variability, and frequent rainfall extreme events due to Mediterranean climatic conditions.
Rugged landscapes with steep slopes, large elevation differences and areas highly dissected by torrential steams.
Surface geology favouring the formation of soils very sensitive to drought and erosion.
Lower rates of soil formation than soil loss, resulting in inadequate depth for roots to grow and low water storage capacity.
Four millennia of human actions including overgrazing and forest fires.

Studies conducted in the context of the EU research project DESERTLINKS have shown that land degradation and desertification risk in pastures is affected by socio-economic factors and land management characteristics such as land ownership, farm size, period of land use, erosion control measures and controlled grazing (Figure 1). If the land in question is rented, the main concern of the land user is overexploitation of the natural vegetation without applying any erosion control measures. In recent decades, degraded agricultural land in Greece has been abandoned and converted to pasture. In such cases, the land presents a lower desertification risk because soils are relatively deeper with lower slope gradient than the surrounding grazing land. The period of existing land use type has decreased desertification risk. Controlled grazing is a major management issue for reducing desertification risk in pastures. In some cases, land is fenced and animals are moved from one place to another to avoid overgrazing.

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Figure 1. Important characteristics affecting desertification risk in pastures. Source: (Kosmas 2004)

Desertification in pastures is either reversible or irreversible depending on the characteristics of the land. In cases where soil moisture has been depleted beyond the tolerance level of the economically and environmentally valuable plants, but rootable soil depth has not been decreased below critical thresholds, desertification is reversible. Irreversible desertification has occurred in areas in which accelerated soil erosion has permanently reduced rootable space and the water storage capacity of the soil is below the levels needed for growing plants. Such cases are mainly found in areas with soils formed on limestone.

Desertification in grazing land in Crete is a very important issue. Based on the Greek National Action Plan for Combating Desertification (Greek National Committee for Combating Desertification 2001), grazing land in eastern Crete is under high desertification risk. Furthermore, grazing land located in the Asteroussia and Psilorites Mountains is mainly characterized as critical or sensitive to desertification. The evolution of the natural vegetation of Crete followed the turbulent history of the island (Bambakopoulou 1985), starting with the first episode of degradation during the Minoan civilization. Cretans, moved into the mountainous areas, clearing forests for cultivation and animal breeding. Later, in the period 327-287 B.C., in his book "About the history of plants", Theophrastus, the father of Botanical science, refers to the great spreading of cypress forest in Crete.

During the invasion of Venetians in the 13th century, colonization of the uplands and mountains took place again. During this occupation, many forests were cleared to produce timber for exports, especially timber from cypress for ship-building. The Venetian occupation was followed by the Turkish invasion in the 17th century. During this period, forest fires were used to sabotage the economy. After the revolution against Turkish occupation (ca. 1900 A.D.), shepherds, who until that time remained on the high mountains, started moving to the lowland for the winter. In the meantime, forest fires continued in the densely vegetated areas to create new pasture-lands. The number of sheep and goats continued to increase, resulting in overgrazing of the area and reduced regeneration of the natural vegetation.

Until 1920, the slopes of the Asteroussia Mountains (south of the Messara Valley) were cultivated with cereals. As mechanisation could not be applied in these areas, they have been abandoned and natural vegetation consisting mainly of phrygana has returned. Although the natural vegetation in the Asterousia area shows a capacity for succession to higher forms, reducing desertification risk, this is not the case since the area is used for grazing during the winter months mainly by the inhabitants of the Psilorites mountainous areas. Overgrazing of the regenerated young plants during this period ceases their growth further degrading the natural vegetation.

LEDD issues in grazing land: Spain and Central Pyrenees

2012-06-14T08:08:11+00:00

Authors: Conceptión Alados, Erea Paz, Frederico Filliat, Maite Gartzia

{xtypo_alert}Editor's note 14Jun2012: Text source D211, section 3.1.4{/xtypo_alert}

In the Pyrenees, as in other mountainous areas of Europe, reforestation has taken place since the middle of the 20th century, essentially for socio-economic reasons (MacDonald et al. 2000; Dullinger et al. 2003a; Lasanta et al. 2006; Mottet et al. 2006). Land use change in traditional managed ecosystems has been identified as the key threat to ecosystem services and human well-being since the second half of the 20th century (Millennium Ecosystem Assessment 2005) and needs to be considered by new policies, especially regarding biodiversity targets. These changes concern the abandonment of grazing practices on slopes and intensification of land use in the valley bottom. Degradation, from the viewpoint of grazing value, involves the loss of productivity of grasslands. The major cause is replacement with unpalatable shrubs. In addition, the productivity of forage can also be greatly reduced by soil erosion, which leads to direct loss of soil nutrients (nitrogen and phosphorus). These processes are causing long-term changes in pasture conditions and productivity (representing slow variables). In particular, the abandonment of transhumance and the replacement of sheep by cattle have important consequences on the conservation of alpine and subalpine grasslands in the Pyrenees.

As a result of land-use changes, many former pastures and cultivated areas are undergoing succession changes towards shrublands and forests (García-Ruiz et al. 1996; Molinillo et al. 1997). This increasing abandonment of agricultural land is thought to be one important driver for decreasing biodiversity (Bernaldez 1991; Alados et al. 2007), which is particularly relevant in this mountain range considered as one of the main biodiversity hot-spots of Europe. After abandonment, the rate of vegetation succession varies depending on the physical characteristics of the area. During the last 30 years, woody encroachment has increased at a rate of 47 percent (Bartolomé et al. 2005). Echinospartum horridum together with Juniperus communis and Buxus sempervirens are the most common species in woody encroachment processes in the Central Pyrenees. E. horridum has increased by seven percent of land cover between 1981 and 2005 in the Ordesa and Mote Perdido National Park, with an encroachment speed of around 2 m year-¹ (Komac et al. in press). Grassland invasion by shrubs is also having an effect on the diversity of grassland species, with the loss of close to 40 percent of species richness (Komac 2010).

Grazing management was traditionally regulated by local organisations such as the Broto Valley Mancomunity (founded in the 13th Century) and the Casa de Ganaderos de Zaragoza. Recently, in response to the increased importance of conservation protocols, a number of actions have been taken to conserve existing landscapes and the indigenous fauna and flora of the Pyrenees. Examples of such actions include the creation of the Ordesa-Viñamala Biosphere Reserve (Man and Biosphere Program, UNESCO) and Sites of Community Importance and Special Protection Areas (Natura 2000 network) for European protection. From 1986 onwards, the Common Agricultural Policy (CAP) of the European Union appears to be the main force in shaping the Spanish agricultural system (Plieniger 2006), supporting meat production. This has resulted in further changes in agriculture, especially an intensification of cattle farming (Plieninger 2006) and resulted in further abandonment of pastures and agricultural fields due to the abandonment of sheep farming. In 2007, the Spanish Government adopted two laws for the protection of rural areas, traditional agriculture and biodiversity. The law “Ley para el Desarollo Sostenible del Miedio rural” had as its principal objective the maintenance of the rural population and activities associated with a better quality of life. The law: “Ley del Patrimonio Natural y la Biodiversidad” was created with the objective of habitat protection and for the control of the impact of urban and industrial areas, and the prohibition of major land use change, which can negatively affect protected areas.

LEDD issues in grazing land: Timahdit

2012-06-14T08:04:04+00:00

Author: Ahmed El Aich

{xtypo_alert}Editor's note 14Jun2012: Text source D211, section 3.1.3{/xtypo_alert}

Nowadays, changes in landscape spatial structure due to human activities are a concern, especially for biodiversity conservation. Habitat conservation is affected by the human demand for housing, arable land, freshwater and manufacturing, increasing land degradation and climate change and consequently threatening ecosystem functioning rising the risk of further extinctions. Succession processes due to changes in land use are typical of rangeland ecosystems as a response to disturbance. For instance, during the last 50 years, the population in the Maghreb has increased considerably, leading to overexploitation of rangelands and desertification (Kebrom and Lars 2000; Olson et al. 2000; Alados et al. 2004).

In the Middle Atlas in Morocco, ecological integrity of the pastoral systems that sustained natural resources for long time, depended on mobility that relied on local land management institutions developed by locals to regulate land utilization (Benchrifa 1990; El Aich and Waterhouse 1999). Conversion of these areas into open access systems, when the local land management institutions changed, resulted in an increase in the use of the grazing areas. In addition, under demographic pressure and economic change, these systems are becoming more sedentary. Sedentarisation in the summer rangelands of the Ait Arfa du Guigou, where the LEDDRA study site is located, is a consequence of the breakdown in the double transhumance that regulated the use of land resources (Bourbouze 1999; El Aich and Waterhouse 1999). In the past, the double transhumance concerned the lowlands in winter and the highlands during summer. Conversion to agriculture of the lowlands reduced the grazing areas and caused a breakdown in the double transhumance. Consequently, herders reduced their mobility and settled in the summer high grazing lands. Herders started to continuously graze pastures that had previously been grazed on a seasonal basis. This change resulted in the invasion of pastures with species with low nutritional value; reduced the carrying capacity of these rangelands; reduced the diversity of pastures; increased the cost of meat production for producers as a result of the need to buy more feedstuff; prompted farmers to switch to different products, in particular crops with higher added value (potatoes and onions) and made the system more agro-pastoral rather than pastoral.