The value of silvopastoral agroforestry systems and challenges for their future

Key words: traditional practices, ecosystem services, tree and animal component, climate challenges

Professor

Department of Forestry and Natural Environment Management, Agricultural University of Athens, 36100, Karpenissi, Hellas pantera@aua.gr

Silvopastoral Systems In Brief

Silvopastoral are those land-use systems in which trees (or other woody perennials) are combined with pasture and livestock on the same unit of land (Mosquera et al. 2018). Grazed open forests can be characterized as silvopastoral systems since their relatively open crowns permit the growth of a lush understory of herbaceous and woody species, mostly evergreen, which means that green leaves and twigs are available as forage throughout the year.

Silvopastoral systems are inextricably linked with the Greek natural environment and traditions and should be protected and preserved as part of our heritage for future generations

Silvopastoralism can be considered one of the oldest land use systems and represents an exceptional example of harmonious co-existence of humans, livestock and nature. Since the early days of humankind, humans raised flocks to ensure animal products for their survival. Based on Le Houerou (1981), raising livestock in the eastern Mediterranean began as early as 10,000 BC whereas by 3000 BC this practice had already been spread to the western part of the region. Mobile pastoral communities have been, and still are in many parts of the world, moving their herds through rangelands, in search of fresh forage and water, making the most out of scarce resources.

Silvopastoral are complex agroforestry systems and can be characterized based on their components which are trees (species composition), grazing animals and the presence of man (ownership-management). Based on the woody component, silvopastoral systems can be distinguished into coniferous and broadleaved systems (Papanastasis 1996). These systems differ according to the prevailing climatic conditions, their structure and management in the past. Thus, the analysis of each of these components, independently of their past and present management, contributes to their better understanding, forming a useful basis for their preservation and future management.

Value Of Silvopastoral Systems

Silvopastoral systems provide numerous ecosystem services depending on their components, ranging from provisional (timber, dairy products, etc.), regulatory (water purification, carbon sequestration, etc.), cultural (recreation, traditional pastoral systems such as transhumance, etc.) and supporting (nutrient cycling, habitat provision, etc., see Papanastasis 2015). Trees in silvopastoral systems provide numerous products such as timber, fuel wood, fence posts, charcoal, fodder, nuts, etc., serving multiple purposes (e.g. water and nutrient absorption, nitrogen fixation, shade, protection from windbreaks and hedgerows, erosion control); trees are managed based on specific needs of the local population and on the availability of natural resources in each area. These two parameters (local population & site) influence the availability of resources, thus forming a variety of systems depending on the specific area, diversified by the traditions of local populations.

One of the most common coniferous silvopastoral systems (Shultz 1986), is that formed by pine trees. Several pine species form silvopastoral systems providing a variety of products. For example, Aleppo pine (Pinus halepensis subsp. halepensis) silvopastoral systems provide fodder for bees, sheep and goats. This system type evolved in time mostly for its resin production and for livestock grazing. Resin collection is an old practice; resin is used as a basic component in many ways and in very different products, one of which is “retsina”, a Greek white wine. Recreation is another popular use for these systems as well as honey production. Similarly, brutia pine (Pinus halepensis subsp. brutia) forms similar silvopastoral systems used for grazing by goats and sheep, timber production, fuel wood, honey, resin, wildlife, meat, and recreation. Other popular conifer silvopastoral systems include those formed by black pine, junipers, cypresses and fir species with their more common products derived from livestock and timber products.

Oak, as the dominant species, prevails in broadleaved or semi-broadleaved silvopastoral systems (Shultz et al. 1986). The shape of the tree as well as its solid wood structure, have for centuries greatly influenced the economy, artworks and civilization of the areas where it grows , providing a variety of goods ranging from meat and dairy products to charcoal and acorn-derived products. Other broadleaved tree systems are those of chestnut (Castanea sativa) and walnut ((Juglans regia). They greatly support livestock and wild animals contributing to the conservation of biodiversity. They offer multiple products such as nuts, high quality timber, fruits, honey, fuel wood, wildlife, meat, recreation etc. The olive tree also forms traditional silvopastoral systems. Olive orchards are frequently described in the Bible as the grazing land of thousands of sheep. Its silvopastoral systems also include orange, almond, walnut, apricot, fig trees and poplars, as well as various grazing animals. Two systems with increasing interest and value are the ones formed by the carob (Ceratonia siliqua) and the mastic tree (Pistacia lentiscus), providing a variety of products including dairy, fruits, chocolate substitutes (from the pods) and mastic by-products (gum, oil, lotions etc.). Other broadleaved- ree silvopastoral systems include those formed by the heather tree (Erica arborea, whose root wood is used for the construction of smoking pipes) and white mulberry (Morus alba, for silk production, a very old practice going back to the Byzantine times), fig (Ficus carica, for fruits production) and the poplarsheep silvopastoral systems. It should be noted that the fig silvopastoral system is a very old one, well adapted to the dry and poor areas, providing fodder for sheep and goats, rendering it an interesting choice under the challenging environmental conditions of climate change.

The grazing animal species component of silvopastoral systems (Papanastasis 2015) depends on local environmental conditions (and, therefore available fodder) and traditions, ranging from sheep and goats, dominating in Mediterranean countries, to cattle and reindeer in northern countries. Goats have been blamed many times as the main cause for the destruction of the natural environment, neglecting its key cause which is overgrazing and mismanagement in general. On occasions when resources shrank considerably, people living in mountainous regions over- or misused the ecosystems. Grazing animals represents a cash income to the farmer through selling meat and milk products, nutrient transfer from forage to soil through their droppings, a successful way for sprout removal, and contribute to soil organic matter cycling. Another important contribution of grazing animals to ecosystems is that of reducing understory biomass and, subsequently, reduce forest fire risk. This raises a very important issue, especially after the devastating forest fires in recent years and deserves to be further investigated.

Present And Future Challenges

Silvopastoral systems have supported local economies in many poor mountainous regions where available resources are limited during the winter period. However, the lack of holistic management in many regions has resulted in the gradual degradation of many traditional silvopastoral systems. Glorious past oak silvopastoral systems are nowadays only used for grazing, especially by sheep, and are also declining due to overgrazing, abandonment and land-use changes. The present unwillingness of farmers to practice silvopastoralism or pass on their knowledge to their successors, poses a major threat that may lead to their disappearance. Young people seem to be averse to pastoralism. In many areas the price value of land has increased in favor of other uses which, in combination with the high labor costs, has driven many locals to other occupations (mostly within the tourism industry), or to more intensive agricultural practices rather than farming and pastoralism. Additionally, overgrazing in combination with frequent forest fires or illegal logging has seriously degraded the environment in certain areas prohibiting any further agricultural or pastoral use. Cheap chemical substitutes have decreased or even diminished the economic value of natural products such as pine resin or acorn-cups derived tannins. Decreased grazing of silvopastoral systems favors the development of a dense, flammable understory biomass partly responsible for the frequent forest fires and the subsequent change in land uses (Mosquera-Losada et al. 2018). These systems are directly related to biodiversity and their degradation may lead to the disappearance of many valuable species.

Silvopastoral systems are of great importance not only for their environmental value, but also for their value as traditional land-use systems (Papanastasis 2015). Most of these systems have supported the local economy of many rural areas providing inhabitants with the means to survive through eras of famine and wars. So, even in the lowlands, silvopastoral systems were, are and must continue to be used for their multiple products and services.