Abstract
Recently, the increasing human population, the increasingly affluent lifestyles, the increasing needs for energy and other resources, and the requirement to store increasing levels of atmospheric carbon dioxide is generating more and more pressure on land. Furthermore, fossil fuels must be replaced by sustainable, renewable resources in the very near future. In Europe and its already intensively managed land, inappropriate biofuel production will cause additional pressure on soil and water resources, on social and on ecological functions of forest and agricultural ecosystems. 21 Innovative solutions are required that combine high productivity with equivalent or enhanced levels of other ecosystem services that also allow adaptation to changing climatic conditions. In this context the term “ecosystem services” can be defined as follows: Ecosystem services refers to a wide range of conditions and processes through which natural ecosystems, and the species that are part of them, help sustain and fulfil human life. These services maintain biodiversity and the production of ecosystem goods, such as forage, timber, biomass fuels, natural fibres, and many pharmaceuticals, industrial products, and their precursors. The harvest and trade of these goods represent important and familiar parts of the human economy. Combining forestry and agricultural systems in agroforestry systems seems to be a promising solution. Agroforestry systems are traditional land management systems that are used throughout Europe even today. These systems are defined as sustainable ways of land use which integrate both agricultural and forestry practices on the same land and at the same time. They are of particular significance to marginal regions and degraded lands where the land use system represents an alternative to land abandonment and afforestation, leads to diversification of land use and offers new socio-economic benefits including tourism and recreation. Agroforestry systems improve the efficiency of utilisation of resources (light, water, soil, nutrients), improve microclimatic conditions within the system (reduction of wind speed, balancing temperature and soil moisture), can help mitigate severe soil erosion problems and nitrate leaching, enhance landscape biodiversity (increased structural heterogeneity in the landscape), lead to an overall high biomass production for material or energetical conversion (fuelwood), and thus matching the increasing demand for a self-supply with bioenergy in rural decentralized areas. Furthermore, with the integration of hedgerows, as it is done within alley cropping systems, a perennial tree component is introduced into conventional cropland. If the trees are managed as short rotation plantations the plants remain for several decades at the sites and accumulate carbon in their biomass above and below ground. Through litter fall this biomass is injected into the processes of decomposition, which supports the formation of vital soil biology and a growing soil humus pool with positive influences on soil quality and thus agricultural production. For this reason, in the temperate zone, agroforestry systems attract more and more public attention as they offer a promising and comprising way for adapting agricultural production to Climate Change and providing comprehensive ecosystem services. While in-depth knowledge was established for tropical and subtropical agroforestry systems, agroforestry in temperate regions (with exception of the United States to some extend) is relatively new and scientifically not well investigated. Recently, some international projects (e.g., EU project ‘Silvoarable-agroforestry for Europe’, Acronym SAFE; www.montpellier. inra.fr/safe/) related to land use adaptation to Climate agroforestry have been initiated within the European Union. Although long-term agroforestry expertise is available, many of them lack scientific rigour. Several interrelated and site-specific factors ranging from agroecological conditions to system management practices influence the rate and extent of carbon sequestration, so that generalizations are difficult. Furthermore, widely and easily adoptable methodologies are not available for estimating the carbon sequestration potential and other benefits. In spite of these, there is an increasing demand for developing “bestbet estimates” based on the current level of knowledge and experience for multifunctional land use and the simultaneous food, fodder, fibre and fuel production. A comprehensive assessment of the ecosystem services in agroforestry systems in temperate regions should consider: 1. A biophysical assessment: Evaluation of the potential to produce biomass and food modelling of system interactions identification of performance, limits and constraints on different areas (e.g. degraded areas, brownfields and post-industrial regions). 2. An evaluation of the carbon and nutrient budgets: Investigation of the impact of C sequestration for soil organic matter and biomass pools as well as of microclimate modification by trees on soil organic matter stabilization processes evaluation of the nitrogen and phosphate dynamics 3. An assessment of landscape biodiversity: 22 Assessment of the potential impact of agroforestry on biodiversity at landscape scale evaluation of the impact of the selected tree species in homogeneous arable lands investigation of the relationship between biodiversity and the proportion of the area occupied by non-arable (including agroforestry) and arable habitats. 4. A valuing of the benefits and sustainability: Exploration of the sustainability functions and socio-economic cross-cutting issues of agroforestry systems, valuation of economic benefits of commercial and experimental agroforestry practices, assessment of the current state-of-the-art thinking on the ecosystem and economic benefits of integrating trees on farms (identification of best practice). These key issues are relevant to policy by providing current and reliable information on the interactions between land management, ecosystem services and society. Further studies are needed to document to which extent a more widespread introduction and targeted design and implementation of agroforestry systems can further optimise the level of provisioning ecosystems services from a limited area of land. Agroforestry management systems can have interesting opportunities on an economic and landscape ecology level under certain conditions. The objective must be to research if and when agroforestry systems are a valid option to traditional methods.
