An interactive model to assess pathways for agriculture and food sector contributions to country-level net-zero targets

The Green Revolution, marked by mechanization, new crop varieties, and intensive pesticide/fertilizer use, mitigated global hunger. In the UK, this led to significant production increases (40% for crops, 90% for livestock) exceeding population growth (30%). Efficiency gains reduced land requirements by 10%. However, this intensive approach resulted in substantial negative sustainability impacts. Synthetic fertilizer use, while decreasing since 1990, remains a major contributor to nitrous oxide emissions (77% of UK agricultural emissions), water pollution (sediments, nitrates, phosphorus), and biodiversity loss (60% decline in priority species, 97% loss of wildflower meadows). Pesticide use also contaminates ecosystems and food. Dietary changes have led to increased food-related diseases and mortality, and significant food waste (10 Mt in 2018). Although food and agriculture emissions fell 13% since 1990, primarily due to reduced ruminant livestock, increased imported soybean cake for livestock feed contributes to deforestation in Latin America. The UK's food self-sufficiency has also declined. The UK's 2050 net-zero target requires balancing emissions sources and sinks. Existing agri-food pathways often focus on sustainable intensification, neglecting critical sustainability issues like biodiversity and landscape restoration. This techno-optimistic approach risks maladaptation and mal-mitigation, hindering transformative change. The need for widespread multi-sector action to change food production and consumption necessitates understanding alternative pathways. This paper presents ARISE, an interactive model enabling stakeholders to investigate relationships and trade-offs between key system variables, promoting a common language and agnostic exploration of alternatives. A collaboration with the European Environmental Bureau (EEB) demonstrates ARISE's application in developing a UK agroecological pathway.

The literature on food and agriculture system transitions is less developed compared to energy system transitions, particularly regarding detailed GHG mitigation pathways and agroecological approaches. Most studies focus on sustainable intensification, often neglecting crucial sustainability challenges. Several pathways have been proposed to achieve the UK's net-zero target, often relying on sustainable intensification and dietary shifts, but these approaches lack detail and fail to address concerns such as biodiversity and nitrogen cycles. Some research highlights the critical role of dietary changes in shifting towards either agroecology or sustainable intensification. The need to align multiple sustainability objectives and account for heterogeneous stakeholder priorities is evident in the literature.

The ARISE model is an interactive quantitative model linking key mechanics of the UK food and agriculture system. It considers country demography (population growth, age, gender, BMI), food supply (FAOSTAT commodity balance), food waste and losses, food self-sufficiency ratios, supply of land-based commodities for other uses, systemic by-product mechanics, domestic self-sufficiency ratios, harvested land, nitrogen balance, input requirements (fertilizers, energy), land-use dynamics (UNFCCC data), carbon dynamics (biomass, soil carbon), GHG emissions (endogenous and exogenous factors), and other sustainability impacts (SDGs). Users set ambition levels for various levers (social behavior, policy, technology) to assess sustainability impacts. Up to 200 levers can be individually set or aggregated. The model considers climate scenarios, international production systems, social behavior (diet, waste), self-sufficiency levels, biomass supply, crop and livestock production systems, and land management practices. The co-design process with the EEB involved workshops and remote meetings to develop a pathway reflecting their scenario narratives, expressed as ambition levels in ARISE. The model highlighted trade-offs, leading to iterative pathway refinement. Data sources included FAOSTAT (1961-2017), Eurostat, UK official statistics, and UNFCCC inventories (1990-2017). Future time series ambition levels were calibrated against scientific literature, ranging from least to most ambitious scenarios.

The EEB pathway, developed using ARISE, resulted in a 50% reduction in meat and a 45% reduction in dairy product consumption, along with a 50% cut in food waste. It involved a shift to agroecological practices, including phasing out imported soybean and palm cakes, reduced livestock density, increased grassland use, and the implementation of cover crops, no-tillage, and intercropping. Crop yields were projected to decrease by 10-45%, reflecting the shift to lower-input practices. The UK aims for self-sufficiency in indigenous crop-based commodities. The pathway projects a decrease in the livestock population by 23% by 2050 and a decrease in total food supply by 15%, with meat and dairy supply dropping by 50% and 36% respectively, while pulses and oil crops increase significantly. The model projects that the food and agriculture-related emissions would be halved by 2050. Carbon sequestration was significantly enhanced through agroecological practices, with net-zero emissions reached around 2040 and a net emission sink of -14 MtCO2eq by 2050. This decrease is largely driven by behavioral changes, with agroecological practices enhancing carbon sequestration in agricultural soils and reforestation. Compared to other pathways (Climate Change Committee, Centre for Alternative Technology), the EEB pathway requires a moderately higher effort in dietary change but lower effort in waste reduction. Other pathways rely heavily on technology-optimistic assumptions (yield gains, BECCS) while the EEB pathway prioritizes carbon sequestration and biodiversity conservation.

The EEB pathway demonstrates that achieving net-zero in the UK agriculture sector is possible with a less technology-dependent approach than other pathways. The different pathways highlight contrasting strategies: the EEB pathway prioritizes agroecology and dietary change while other pathways lean towards technological advancements (e.g., BECCS, GMOs). The reliance on technological solutions in other pathways raises concerns about potential risks and uncertainties. While all pathways emphasize dietary changes, the EEB pathway demonstrates that significant emission reductions are attainable with a more moderate shift toward plant-based diets, preserving arable land and supporting a more balanced approach. The ARISE model enabled the EEB to navigate trade-offs between sustainability objectives and develop an internally consistent agroecological pathway not readily found in existing literature. The model's interactive nature fostered a learning process that improved the understanding of the consequences of different policy choices.

The ARISE model offers a valuable tool for stakeholders to collaboratively design and evaluate pathways towards a sustainable food and agriculture system. The EEB case study demonstrates the model's ability to generate alternative pathways emphasizing agroecology, highlighting the importance of considering multiple sustainability objectives and balancing technological advancements with behavioral and systemic changes. Future research should focus on incorporating economic cost analyses, refining the model's capabilities to assess health-diet dynamics and biodiversity benefits, and exploring effective policy interventions to ensure the feasibility of ambitious pathways.

While ARISE provides a comprehensive framework, certain limitations exist. The model doesn't fully account for the economic costs of the different pathways, which requires further development. Some impacts, such as health-diet dynamics and biodiversity benefits, are currently not fully captured. The model relies on existing data and projections, which inherently contain uncertainties. Furthermore, the co-design process, while effective, relied on remote collaboration, potentially impacting the depth of interaction. Finally, the model's user-friendliness could be further enhanced to improve accessibility for non-modellers.