Co-delivery of food and climate regulation by temperate agroforestry (CALIBRE).

GGR Topic-Specific Project Type

Context
In absence of human habitation, nearly all land in the temperate biome would be covered by forests holding large quantities of carbon within the trees and the soils. Historically, much of these forests have been cleared to make way for agriculture, releasing most of the carbon into the atmosphere. Converting agricultural land back to forestry therefore offers significant potential for greenhouse gas removal (GGR), however in most instances this would come at the cost of reduced food production. Existing land capability studies [4] indicate that the best locations for afforestation are in some of the most productive agricultural areas, highlighting the conflict between forestry and agriculture.

GGR opportunity
Agroforestry (AF) is a well-understood land use system which purposefully integrates trees with either arable or pastoral food production. AF is not novel, its many benefits include crop diversification, improved water and nutrient cycling in agricultural landscapes and provision of habitats for biodiversity. A well-planned AF system allows for continued food production, while a small percentage of the land is dedicated to tree planting - usually in single line formations. However, the combination of modern farming methods, existing regulatory regime and the historical distinction between agriculture and forestry currently place 'socio-economic' constraints on wider application of this system within the UK.

Research questions and plan of work
This proposal will address the research questions and objectives through five integrated work packages:
Work package 1 will estimate GGR potential of AF in the UK under a combination of time (timeframes of adoption of AF across the landscape) and intensity (the proportion of land dedicated to the tree component). The Sheffield Dynamic Global Vegetation Model (SDGVM) will be used to investigate the interaction between crops/pasture and trees. We will develop a new plant functional type to describe and model AF systems and to predict the change in carbon stocks in trees and soil (i.e. the additional GHG removal) when compared to current agriculture.
Work package 2 will evaluate the current barriers to AF adoption related to policy and socio-economic considerations. We will develop value propositions designed to incentivise farmers and landowners to commit to AF in both arable and pasture settings.
Work package 3 will build on the outcomes of work package 1 and 2 and develop detailed examples of field-scale benefits of AF across different farming systems (arable/pasture), four UK agro-climatic regions and on varying soil types. We will use workshops with farmers to develop realistic scenarios for AF deployment, taking into account wider benefits of avoided emissions through better soil and nutrient management.
Work package 4 will upscale the farm-level impacts of GHG removal 'business case' to correspond to the GHG removal scenarios (work package 3) and the evaluation barriers and opportunities of AF adoption (work package 2) to generate agricultural, environmental and energy policy recommendations.
Work package 5 will focus on integration and management. We will coordinate and integrate the research development between work packages and work with policy and farming communities through a series of targeted workshops to identify current barriers limiting adoption of AF on a wider scale.

Interdisciplinarity
Our interdisciplinary approach brings together scientists, social scientists and economists across the Food and Environment Research Themes at the University of Reading. Expertise of collaborators spans research on carbon cycles in agricultural (including AF) and forest ecosystems, modelling plant and soil C dynamics, national and farm-scale rural economy and policy. All have experience in working on interdisciplinary projects and recognise the benefits of this approach to deliver viable solutions.

The proposal will focus on two key issues: assessing the potential of agroforestry for GGR and identifying current economic, social and political barriers and trade-offs hindering its wider adoption (i.e. the 'weakest link'). CALIBRE addresses multiple priorities identified in the call, spanning negative emissions from the early stages of adoption, sustainable development in disadvantaged areas, social impacts, public and stakeholder acceptability, biodiversity conservation and ecosystem function.

Looking at an agricultural practice with wide applicability and adaptability to a diverse range of environments, the project has the potential to deliver information on key uncertainties and GGR potential of AF within the 50-100 year planning horizon. Crucially, this 18 month project has potential to deliver real benefits to increase GGR through AF as part of a suite of integrated measures before 2020. Stakeholders likely to benefit from project findings include:

Farming community
AF offers significant potential for farm income diversification, whether through sales of timber and other tree-related products, or via monetisation of carbon sequestration capacity of AF systems. There is evidence that establishing AF positively affects farming ecosystem stability, offering more predictable and reliable production year-on-year [5]. The project will contribute to the ongoing debate on the merits of AF within modern food production systems. The farming community is currently incentivised to decrease fertiliser application for economic and environmental reasons, improving knowledge and information base on AF may decrease direct (N2O emission from soils) and indirect (fertiliser manufacture) GHG emissions associated with agriculture.
With specific reference to the UK (Brexit), but also on European (CAP reform) and global scales, farmers will benefit from access to information on likely changes and impacts of regulatory climate. The project will engage with policymakers to assess potential development regarding AF adoption and support mechanisms.

Energy generation
As the UK seeks to decarbonise the power system, intermittent renewable generation (wind and solar) still requires support from flexible thermal generation plant to ensure system stability [6]. Organic biomass offers a low carbon option to fill this role, however utilising existing residue and timber biomass supply may not be sufficient or sustainable. This project will predict the capacity of AF systems to supply feedstocks for electricity generation in the UK and to eventually contribute to negative carbon emissions once Carbon Capture and Storage technology matures [7]

Natural flood management and drinking water supply
Water retention and filtration by the landscape is one of major challenges associated with catchment management. The project will inform on the potential of AF systems to reduce runoff generation as a form of natural flood management. The UK winter floods of 2015 alone are estimated to have cost the UK over £5 billion. Further, by retaining nutrients within trees located in fields, AF systems are likely to improve raw water quality and thus reduce energy use at drinking water treatment works.

Policy and rural economy
At the national scale, climate change mitigation policy will benefit from clear indication of the potential of AF to contribute to current UK commitments on GGR. Large-scale establishment of AF systems will also result in a generation of new employment opportunities and diversification of farm income in rural areas; issues of interest to local, but also national policymakers.

Wider public
Application of AF in UK landscape is likely to have a visual impact across several scales of the public-landscape interaction. The project will indicate how AF might affect a range of benefits public derive from the landscape; from aesthetics and recreation to biodiversity and microclimate regulation.