Modelling the production impacts of scaling up agroforestry systems in England and Wales

Abstract

CONTEXT: Land managers and governments face the challenge of using finite land, labour, and financial resources to achieve multiple objectives. Agroforestry, the integration of trees with farming, is promoted as a strategy for achieving multiple policy objectives relating to productivity, climate change and biodiversity. However, regional and national-scale studies validating its effectiveness remain limited. OBJECTIVE: Our study aimed to model the impacts of scaling up agroforestry on food and fibre production in England and Wales. We developed nine agroforestry scenarios combining three tree types (apple, poplar, and short rotation coppice (SRC) willow) at three planting densities. Each scenario scaled agroforestry to all suitable agricultural land (representing 79% of total agricultural land) as a simple modelling objective, rather than a realistic target. METHODS: We used the well-established Yield-SAFE model to simulate tree-crop/grass interactions at low, medium, and high tree densities, and inputted the resulting yields into the Optimal Land Use Model (OLUM), a linear programming model with the objective of maximising food energy production under defined constraints. The OLUM was validated using baseline data. RESULTS AND CONCLUSIONS: Scaling up agroforestry increased domestic supply of tree products, for which the UK is heavily import-dependent. However, this came at the expense of the calorific value of food production, which decreased by 3% to 45%, depending on tree type and density. The largest reductions were observed in arable and vegetable crops, due to reduced area and yields. Ruminant livestock outputs were least affected, supported by increases in grassland area. Timber and apple agroforestry systems were predicted to be more land-efficient than equivalent monocultures (for apples, traditional orchards), based on land equivalent ratios. SIGNIFICANCE: Upscaling agroforestry could reduce import reliance on tree products while contributing to environmental objectives. To minimise reductions in domestic food supply, policymakers should prioritise agroforestry in pasture-based systems and support wider food system changes. Design improvements could lessen trade-offs associated with tree planting in arable systems. Future research should investigate how scaling up agroforestry systems affects greenhouse gas emissions, biodiversity, soil, water, and the general resilience of the farmed landscape.