Responses to LEDD in cropland: general

Editor's note 3 May 2012: Text source D111 section 4.4

Responses to LEDD in cropland types are categorised as physical/technological; economic; social; institutional/legal; research; and educational/communication. This section of LEDDRIS briefly discusses examples of physical, technological and institutional responses to LEDD, although these responses cut across other themes in that they also include elements of economic, social, research and education-type responses. Policies (as institutional/legal responses) also clearly play a key role in responding to LEDD and these are briefly discussed here. However, ** change link policy responses to LEDD are the subject of the joint Deliverable Reports co-ordinated by WP6 and are therefore described in more detail in those reports.

Intensification of agriculture

Agricultural intensification is focussed on increasing the yields per hectare of land used. Intensification utilises technical approaches to improve output and soil quality using high inputs of mineral and organic fertilizers, protecting plants from pests and diseases, increasing mechanisation, developing irrigation, improving land, improving crop varieties and introducing specialisation (Gliessman  1998; Zhang et al. 2007; Tilman et al. 2002; Pearson 2007).

Expansion of agriculture

Historically, expansion of agriculture into forests, grasslands, and wetlands has been the main driver of ecosystem conversion. Worldwide, humans have converted approximately 29 percent of the land area (almost 3.8 billion ha) to agriculture and urban or built-up areas (Mock 2000).  Conversion of land to cropland and managed pasture has affected some 3.3 billion ha (roughly 26 percent of the land area). Agriculture has displaced one-third of temperate and tropical forests and one-quarter of natural grasslands (Mock, 2000).

The effort of clearing natural vegetation has been made easier by the use of heavy machinery. Studies conducted in south-western Chania (Crete-Greece) have shown that 30.5 percent of agricultural land was derived from cleared land between 1960 and 1997 (Kosmas et al. 2007). Analysis of factors driving the selection of land for clearance shows that the most important factors were distance from the coast, altitude and water storage capacity.

The expansion of cropland into hilly areas around the Mediterranean region has been accompanied by intensive cultivation and overgrazing, which has resulted in accelerated erosion and the formation of badlands with very shallow soils. Erosion rates measured in Mediterranean badlands vary widely from 0.4 mm y-¹ to 1.7 mm y-¹ (Yair et al. 1982; Benito et al. 1992). In cases where adequate plant cover has been achieved (greater than 50 percent)  after clearing natural vegetation and planting olive trees, a new agro-ecosystem has been established which can provide effective protection to the environment. A typical example is the island of Lesvos (Greece) where the expansion of olive groves into hilly areas previously occupied by pine or oak forest has not significantly affected land degradation (Marathianou, et al. 2000).

Land abandonment

Land abandonment represents a major change in land use. Land abandonment in the Mediterranean occurs as a result of external driving forces, such as market changes, or internal changes when, for example, the soil has been depleted to the point where it restricts plant growth. By 2000, between eight and 15 percent of agricultural land in the Mediterranean was abandoned. Land abandonment is often considered as a cause of desertification but this is not always the case, as the re-establishment of natural vegetation systems which may prevent further erosive processes often follows (Kosmas et al. 2006b).

Land terracing

Land terracing is a traditional soil conservation technique for sloping lands (Samson 1986). The benefit of land terracing is the conservation of soil and water. The purposes of terracing are to: (a) redistribute soil material in sloping areas with shallow or moderate soil depth; (b) increase plant rootable depth; (c) improve access and facilitate operations; (d) clear stones which can interfere with cultivation; (e) decrease surface runoff and increase water absorption; (f) control soil erosion (Kosmas et al. 2006c).

Techniques of terrace construction have changed over time (Grove and Rackham 2001). Originally, land was shaped into a series of nearly level benches or step-like formations bounded on the lower side by an almost vertical bank, usually protected by a stone wall. These structures were narrow and steep-sided so that cultivation with conventional farm implements was difficult or impossible.  The value of traditional terraces has markedly declined due to: (a) difficulties associated with accessibility and use of machinery; (b) decreasing price of agricultural products and increasing labour costs; (c) high input agriculture developed in plain areas; (d) high cost of maintenance; and (e) extensive migration of people from rural to urban areas (Kosmas et al. 1998, Grove and Rackham 2001, Kosmas et al. 2006c)). Modern terraces consist of low-graded channels or levees which carry excess rainfall from the land at non-erosive velocities. Such terraces are broad, allowing mechanisation and can be constructed in areas where soil is relatively deep (Kosmas et al. 2006c).

Expansion of irrigation

Irrigation is any human-induced change in the natural flow of water for the purpose of growing plants. Over the past 50 years, the world-wide area of irrigated agricultural land tripled from approximately 90 million hectares to 270 million hectares, at a rate of over 2.5 percent per annum. The expansion of irrigation has been based mostly on the construction of new dams and reservoirs or, where ground water is readily available, through the use of wells.  Water is usually delivered to fields through canals or pipes. Sources of water include rivers and streams (either through direct diversion or after storage in a natural lake or a water-reservoir) and aquifers.  The rapid growth in food production from the mid-1960s has been largely accomplished by expanding the area of land under irrigation. As a result, water resources may be placed under severe physical, social, economical and environmental stresses, resulting in reductions in annual water availability.

Organic farming

Organic farming is the form of agriculture based on techniques such as crop rotation, green manure, compost and biological pest control to maintain soil productivity and control pests on a farm. Organic farming excludes or strictly limits the use of manufactured fertilizers and pesticides, plant growth regulators such as hormones, livestock antibiotics, food additives, and genetically modified organisms. Intercropping is also used for insect and disease control and to increase soil nutrients. Organic farming relies on ecological processes, biodiversity and cycles adapted to local conditions, rather than the use of inputs.

Organic citrus production in Andalucia, Spain, provides an example of a positive response to LEDD problems caused by mainstream traditional citrus production. In 2010 organic citrus cultivation in Andalusia occupied 2,868 ha. According to the Andalusian Committee for Organic Farming (ASAC), export accounts for 75 percent of production, leaving 25 percent for the domestic market. The main destination is within the European Union; mainly Germany, France and the UK. Organic citrus cultivation in Andalusia is expected to increase significantly in Huelva. Expectations are that large organic orchards will be installed mainly near the coast and in regions of Western Andévalo (Arenas et al. 2011).

Land use and land cover

Land use and land cover change is a general term for the human modification of Earth's terrestrial surface (Ellis 2010). Land-use and land cover can have both positive and negative effects on LEDD.  Vegetation and land use are clearly important factors controlling various processes affecting land and ecosystem degradation such as fire risk and ability of vegetation to recover,  plant drought resistance, soil erosion protection, surface water run-off, soil organic matter content and biodiversity. Traditionally, the use of the soils was based on natural characteristics such as slope, soil quality, and the availability of water. More recently, new cultivation techniques and market forces have made economic issues the main driving force in land use change. For example some hilly areas that were under forest with deep soils were brought under cultivation for the production of cereals (Kosmas et al. 1997). Land use changes in cropland have been driven by various factors including existing policies on crop production (subsidies), macro-economics, population growth, availability of water resources, existing technology and knowledge transfer.

Land shaping

Levelling, smoothing and shaping the land is a process for ensuring that the depths and discharge variations over a field are relatively uniform. Land levelling improves the efficiency of water, labour and energy resource use. The levelling operation, however, is considered as an intensively disruptive practice. Major topographical changes generally reduce crop production in the cut areas until fertility can be replaced. Similarly, machinery traffic can so compact or pulverize the soil that water penetration is a major problem for some time.  

No-tillage or minimum tillage

Although there were many early attempts to cultivate crops without tillage, modern no-tillage research began in the 1940s and was adopted by farmers in the early 1960s.  This approach was first conceived as an efficient soil conservation method and subsequently evolved into an economic and sustainable production system that improves soil physical, chemical and biological properties (Derpsch 1999). No tillage or minimum tillage, often called conservation tillage, is a cultivation approach that has become popular in areas suffering drought or soil erosion.  In a no-till system the number of field operations is often considerably reduced. Often, the main reason for adopting a no-till system is soil conservation.

Tillage practices play an important role in controlling surface crust and affecting seedling emergence. Intensive tillage causes deterioration of soil structure and may cause severe crusting and seedling emergence problems if heavy rains followed by sunny days occur immediately after seeding. Researchers have repeatedly concluded that minimum or no-tillage systems benefit organic matter content and soil structure, and reduce crusting problems substantially creating favourable conditions for earthworm activity and higher microbial populations in soil surface layers (Doran 1980).

Soil erosion protection

Numerous soil erosion control techniques have been developed and are mainly based on the control of major factors affecting soil erosion. In many cases, soil erosion is not controlled by a single practice but by a system composed of a number of actions such as conservation tillage, contour farming, incorporation of plant residues into the soil, terracing, vegetated waterways, and by maintaining vegetation cover (Wischmeier and Smith 1978).

Soil salinisation protection

Traditional farming techniques avoided the problems of soil salinisation by adopting a series of strategies including  the use of appropriate crops and cultivars; crop rotation; irrigation methods; water storage; water mixing; water reuse; and desalinisation (Barett-Lennard 2002, Evett et al.  2000). No single technique can ensure that productivity levels and income are maintained over time. Prevention and reclamation of salt-affected soils requires an integrated management approach including monitoring, technological approaches and socio-economic measures (Iannetta and Colonna 2008).

Institutional responses to LEDD

Effective land desertification protection requires both appropriate land management practices and macro policy approaches that promote sustainability of ecosystem services. Therefore, many responses to combating desertification combine a number of different approaches and actions. National Action Programmes stipulated by the UNCCD have been elaborated by affected country Parties in which the main factors contributing to desertification have been identified and measures necessary to tackle those factors and mitigate their impacts have been proposed.

In areas where desertification processes are at an early stage or are relatively minor, it is possible to arrest the process and restore key services.  Regional Action Plans (RAPs) have been formulated by the former Annex IV group (Greece, Italy, Portugal, Spain and Turkey). This group have highlighted the need for: (a) developing efficient communication with the scientific community, (b) raising awareness amongst all stakeholders in affected areas through education and training, (c) discussing political, social and economic factors and their relationship to desertification. Alongside defining a common basis for understanding and approaching desertification issues, the following priorities provide a basis for sub-regional action plans (SRAP) (Zanola, et al. 2006):

1. Most sensitive areas in terms of desertification hazard
2. Common regional benchmarks and indicators for processes and mitigation
3. Collection, analysis, and exchange of technical and scientific data
4. Exchange of data and information
5. Involvement of civil society within the SRAP process
6. Traditional knowledge and practices safeguarding the quality of north Mediterranean landscapes
7. Connection with other existing regional and sub-regional initiatives

The European Union has formulated regulations for soil erosion protection.  Regulation 1760/87 of the European Commission encouraged Member States to define areas of sympathetic agricultural practices for further support. In the decade 1982-92, the strategy was progressively modified to allow greater support for conservation of the landscape and its component parts. In addition, the Maastricht Treaty (1992) recognized that the European Union must promote measures at an International level to deal with environmental problems and ensure sustainable growth (Corrie 1991).