Chapter 3 systematically assesses the environmental effects of SAFfor a stratified random sample of 19 landscape test sites (LTS) in Mediterranean and Atlantic regions ofEurope.For each LTS, existing geographical and statistical data were compiled, harmonized and complemented by field surveys. LTS were subdivided into a maximum of four land units (LU) using cluster analysis. The LUs were considered to be homogenous with respect to soil properties and climatic conditions and were used to represent farm management units. The LUs were ranked according to their potential productivity from "best land" to "worst land".The impact of SAF was explored by introducing SAF over 10% or 50% of the farm/landscape to simulate "pessimistic" and "optimistic" adoption by the farmer. Two tree densities (50 and 113 trees ha -1 ) were compared and SAF could be implemented in the best or worst quality land of the LTS to simulate different management priorities.
Across the 19 landscape test sites, SAF had a positive impact on the four environmental indicators with the strongest effects when introduced on the best quality land. The computer simulations showed that SAF could significantly reduce erosion by up to 65% when combined with contouring practices. Nitrogen leaching could be reduced by up to 28% in areas where leaching currently is high (>100 kg N ha -1 a -1 ), but this was dependent on tree density. With agroforestry, predicted mean carbon sequestration, over a 60-year period, ranged from 0.1 to 3.0 t C ha -1 a -1(5 to 179 t C ha -1 )depending on tree species and location. Landscape biodiversity was increased by introducing SAF by an average factor of 2.6.
From the beginning of the research, Chapters 3 and 4 were co-ordinated and carried out in the same test sites. While Chapter 3 assessed the environmental effects of silvoarable agroforestry, Chapter 4 evaluated the profitability of the same scenarios as Chapter 3.
Time-series of annual production data and economic data for crops and trees (grants, revenue and costs) for each LTS were combined in the farm-scale bio-economic spreadsheet model FarmSAFE. The economic performance of the arable and silvoarable systems was compared using the infinite net present value( iNPV ) for a time-frame of 60 years (discount rate = 4%).
The Common Agricultural Policy (CAP) payments were modelled for arable and silvoarable systems assuming: 1) No CAP payments; 2) Pre-2005 CAP payments; and 3) Post-2005CAPpayments, assuming in the case of silvoarable systems that a Single Farm Payments would be made to the whole cropped area (whilst cropping occurred) and that 50% of tree costs would be covered for the initial 4 years of the tree rotation.
The analysis inFrancesuggests that walnut and poplar silvoarable systems could provide a profitable alternative to arable and forestry systems, while inSpaina modest restructuring of the amount and delivery of agricultural payments would increase the attractiveness of silvoarable systems of holm oak and stone pine. In the Netherlands, low timber value and the opportunity cost of losing arable land for slurry manure application made both silvoarable and forestry systems uncompetitive with arable systems.
Chapter 5 is the integration of results obtained in Chapters 3 and 4 into a multi-criteria decision analysis (MCDA). ThePROMETHEE outranking approach was used to evaluate the integrated performance of silvoarable agroforestry relative to a status quo, on hypothetical farms in the nineteen LTS inSpain,France, and theNetherlands. The criteria used in the evaluation were soil erosion, nitrogen leaching, carbon sequestration, landscape biodiversity, and infinite net presentvalue,the latter assessed under six levels of government support. The MCDA was not configured to reflect the position of a specific stakeholder (e.g. an NGO might rate environmental criteria higher than profitability, whereas farmers might rate profitability higher than environmental criteria) but a neutral weight distribution was adopted.
InFrance, the analysis showed, assuming equal weighting between environmental and economic performance, that silvoarable agroforestry was preferable to conventional arable farming. The best results were observed when agroforestry was implemented on 50% of the highest quality land on the farm; the effect of tree density (50-113 trees ha -1 ) was small. By contrast, inSpainand theNetherlands, the consistently greater profitability of conventional arable agriculture relative to the agroforestry alternatives made overall performance of agroforestry systems dependent on the proportion of the farm planted, and the tree density and land quality used.
The environmental and economic performance of SAF in Europe is highly variable since each country/region has its specific biophysical and economic conditions. However, inEurope, ecological integrity is increasingly seen as fundamental to economic and social well-being. This work provided an initial approach for an integrated environmental and economic analysis of SAF systems. The findings could be refined to support policy development for silvoarable agroforestry as a new land-use alternative for farmers. At the same time, the framework could be adapted to the investigation of environmental and economic consequences of other land-use alternatives (e.g. new crops, forestation) at the landscape / farm scale.
|Qualification||Doctor of Philosophy|
|Award date||20 Sept 2006|
|Place of Publication||Wageningen|
|Publication status||Published - 2006|
- agrosilvicultural systems
- arable farming
- environmental assessment