Current state of the art
Agroforestry in Latin America
Agroforestry has been defined as a form of multiple cropping which satisfies three basic conditions:
- there exists at least two plant species that interact biologically
- at least one of the plant species is a woody perennial
- at least one of the plant species is managed for forage, annual or perennial crop production.
It is a land management system that optimizes land productivity by involving positive interactions between its components in time and space. It takes advantage of the complimentary relationships between trees, crops and livestock in such a way that the productivity, stability and sustainability of the total system exceed most of the single cases. Its appropriate exploitation is a remarkable opportunity for improving degraded sites, stabilizing fragile ecosystems and is also an ideal farming system for arid and semi-arid recovery and sustainable agriculture.
Agroforestry offers several advantages, such as the possibility of soil enrichment by fixing nitrogen, the improvement of drainage, and the efficient nutrient cycling. It also represents an opportunity for vertical expansion optimizing land productivity and diversity in output to meet domestic needs and improve economy of farmers. Additionally, agroforestry generates high income and minimizes risks in cropping enterprises. It provides long-term investment opportunity, diversifies land use and implements commercial tree cropping, being the best option for absentee landlords. This can generate diversified on-farm employment, wood and non timber forest produce and ensure raw-material supply to forest based industries(PCGI, 2001).
Agroforestry practices can include alleycropping, silvopasture, windbreaks, and shelterbelts, riparian buffer strips (Figure 1) and forest farming. Alleycropping involves growing crops (grains, forages, vegetables, etc.) between trees planted on rows. The spacing between the rows is designed to accommodate the mature size of the trees while leaving room for the planned alley crops (Beetz, 1999). Several configurations of different crops and trees have been experimented successfully in Argentina, for instance Pinus elliottii and P. taeda with mandioca, watermelon, melon, zapallo, cucumber, etc (Kozarik et al., 1997). Additionally, in Uruguay, the combined plantation of maize with Eucalyptus globulus and/or E. viminalis revealed good results (Polla,1997). One of the most researched fields in agroforestry is silvopastural agroforestry or silvopasture, which involves tree and pasture combinations.
Hardwoods and/or pines are planted in single or multiple rows, and livestock graze between them (Beetz, 1999). Silvopasture investigations have been carried out for several years in several Latin America countries like Cuba, Peru, Colombia and Argentina. For more than two decades, there have been investigations and implementations of a series of experiences in the forests of the South American semi-arid Chaco, in order to revert the degradation state in which are the natural resources (Kozarik, et al.1997).
- Figure 1: Riparian buffer
- Figure 2 and 3: Tree windbreak
In a windbreak or shelterbelt system the trees are planted in single or multiple rows along the edge of a field to reduce wind effects on crops or livestock. Windbreaks have been shown to reduce wind impact over a horizontal distance equaling at least ten times the height of the trees. Wind and water erosion are reduced, creating a moist, more favorable microclimate for the crop (Beetz, 1999). In Peru, there have been installed shelterbelts by means of forest species seeds sowing around the parcels, to take advantage of rains, and to manage to protect areas of cultures, and thus to avoid the use of the species Prosopis sp., scabrida Capparis for posts (Pastor, 1996). Threes, grasses, and/or shrubs planted in areas along streams or rivers are called riparian buffers or filter strips.
These plantings are designed to catch soil, excess nutrients, and chemical pesticides moving over the land’s surface before they enter waterways. Such plantings also physically stabilize stream banks and prevent stream bank erosion (Beetz, 1999).
When a natural forested area is managed for both wood products and an additional enterprise, it becomes an agroforestry system (forest farming and special forest products) (Beetz, 1999).
Water management in Latin America
Latin American is the region of the world that posses the highest access to water resources, about one third of the total renewable reserves. According to WRI (2000), only South America contains about 30% of the total runoff of the world, estimated 42650 km3 receiving an annual average rainfall of 1556mm, superior to any other region of the world.
In spite of the great reservoirs of fresh water, these are irregular distributed in time and space, affecting the availability across the region. For instance, in the arid and semi-arid region of South America, representing 26% of the total surface, the rainfall accounts for less than 550mm, having experienced extreme periods of droughts and floods, which have generated an impact on the natural resources, making it difficult to maintain or improve land productivity. On the other hand , two thirds of Central American region is located on the arid Pacific side where only 30% of rainwater drains in an irregular pattern, wich has impaired maintaining a sustainable drying agricultural process.
It is palpable that such climatic conditions, together with the lack of institutional measures for watershed management, have made agriculture a vulnerable and non sustainable activity in dry areas of Latin America. For instance agricultural irrigation amounts today to 69-70% of the water consumption in the region with 18.6 million hectares (0.9% of the total territory) from a potential of 77.8 million hectares.
Regarding the integrated water management in the region, some successful experiences have been identified. For instances, the "Trifinio- Alto Lempa" Plan, aimed to the rationalised use of water resources of the Lempa river, shared by Guatemala, El Salvador and Honduras, is an example of water management of a transbordered water body by the ecosystem approach (UNCCD, 2004).
Regarding the wastewater treatment, in 1998 less than 14% of the 600m3/s of domestic wastewater collected in Latin America had some treatment before being disposed of in rivers and seas, and only 6% had on acceptable treatment (PAHO/WHO,2001), causing the incidence of waterborne infectious diseases among 40% of the population. Furthermore, the explosive urban growth has generated a rapid snd chaotic urbanization of farmlands and has prioritised the use of surface waters for human consumption and the industrial sector. Consequently, the agricultural activity located around the periphery of the cities has been seriously affected and wastewater use has been the only survival alternative. This is reflected on the existence of more than 500.000 ha of agricultural lands irrigated directly with untreated wastewater (Moscoso and Egocheaga, 2002).
Some initiatives have been started by CEPIS, which proposed a model to integrate wastewater treatment and use, by an integrated system that adapts domestic wastewater treatment for its productive use, prioriritising pathogen removal to protect public health, instead of the removal of organic matter and nutrients, which are important for agriculture. This system composed by stabilisation ponds is intented to incorporate also the efficient water management in the basin (Moscoso and Egocheaga,2004).
WAFLA Enhancement of the STATE-OF-THE-ART
WAFLA, as a coordination action, will integrate in a multidisciplinary approach the local and regional initiatives in the fields of agroforestry and integrated water resource management, in order to bring together the traditional and accumulated knowledge pointing out the needed research and technology efforts to propose feasible mechanism to enhance the productivity of agroforestry activities in the arid areas of the region. The consortium will identify the targeted crops, describing the properties, transformation processes and market value, as well as defining the suitable agroforestry/water management systems and the criteria of application according to local conditions.