Co-benefits and tradeoffs of UK climate actions. A systematic Rapid Evidence Assessment and rating of effects on climate adaptation and mitigation outcomes

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Introduction

The aim of this work (from the CS-NOW project) was to build an understanding of the co-benefits and tradeoffs between climate mitigation and adaptation in the United Kingdom (UK) to inform the Government’s efforts to promote decarbonisation and resilience. Knowledge of co-benefits and trade-offs will aid the Government’s identification of no/low regret actions (i.e. actions with little or no trade-offs for either adaptation or mitigation outcomes).

The implications for both mitigation and adaptation of interventions in the UK intended either to mitigate or to adapt to expected climate change (“climate actions”) are intertwined. If mitigation actions are designed without considering climate vulnerabilities and risks, they may be maladapted or lead to wider maladaptation (i.e., by compounding climate impacts). For example, increasing reliance on electricity (particularly from renewable sources) for energy supply to achieve mitigation goals may increase the risk of climate-related failure of the energy system from flooding or storms. Similarly, if climate adaptation actions are selected without consideration for climate mitigation, they may increase greenhouse gas (GHG) emissions.

Assessment approach

To develop understanding of cobenefits and trade-offs between climate adaptation and mitigation the CS-NOW project has:

1. Identified UK climate actions for assessment (see Section 2 in the document in the right hand column).
2. Undertaken a Rapid Evidence Assessment (REA) to identify and extract relevant evidence regarding UK climate actions from peer-reviewed literature and governmental reports (Section 3). REAs use methods developed for full Systematic Reviews to ensure that they are systematic and transparent.
3. Based on the evidence assembled by the REA, rated the effect of UK climate actions on UK mitigation and UK adaptation outcomes, and determined confidence in these ratings (Section 4).
4. Based on the ratings of the effects of UK climate actions, the authors identified key overall findings and caveats, and determined which recommended actions should be the subject of detailed case studies (Section 5).
5. Developed case studies for two low/no-regret actions identified: 1. Soil conservation and 2. Aim to reduce direct emissions from public sector buildings by 75% by 2037 compared to 2017

Analysis and key findings

In general, the assessment determined that nature-based actions have high co-benefits and no trade-offs in terms of the adaptation and mitigation outcomes assessed in this study. In particular, “Active habitat management to increase resilience” and “Soil conservation”, which are actions included in the Independent Assessment of UK Climate Risk (CCRA3, CCC, 2021), have substantial positive effects on climate adaptation and mitigation.

While most of the climate actions identified as having the highest co-benefits and no identified trade-offs are nature-based, other actions, such as “Passive cooling measures” (from the CCRA3) and “Aim to reduce direct emissions from public sector buildings by 75% by 2037 compared to 2017” (from the UK’s Net Zero Strategy) also have large co-benefits and no identified trade-offs. However, both the latter actions encompass nature-based solutions. Passive cooling measures includes urban greening/trees, and reducing emissions from public buildings can be achieved through use of green roofs. See Table 1, below, for a summary of the ratings of these low/no-regret actions.

On the other hand, some climate actions, such as engineered removals, have high potential trade-offs. For instance, engineered removals have a high carbon sequestration potential, but the analysis showed the potential for negative impacts for adaptation around natural habitat and competition with farmland (BECCS), and a high energy penalty (DACCS). Climate actions based on increased electrification have mitigation benefits if they are delivered alongside further decarbonisation of the grid. They otherwise present potential trade-offs for adaptation, including decreased adaptive capacity in the face of increasing extreme weather events that impact energy supply and demand.

Finally, while some actions were rated as having strong co-benefits and low or no trade- offs, these may vary over time. For example, while the action on “Suitable trees, crops, and livestock for future climate in appropriate locations” (CCRA3) has high co-benefits and no identified trade-offs, benefits for climate mitigation may only be delivered over time, especially regarding tree planting. In early stages a plantation may even lead to net carbon emissions, e.g., if planted on former pasture. Implementation of the action also needs to consider the increasing magnitude and frequency of extreme weather events, as well as incremental climate change, if it is not to lead to maladaptation.

Figure 1. Table 1. Summary of climate actions, descriptions and assessment in terms of regrets/trade-offs. (Adapted for this article from Steller et al., 2024)

Explanation of assessment column –  based on the evidence, the effects of each UK climate action on UK mitigation and UK adaptation outcomes were rated. The evidence and ratings are presented in the accompanying workbooks (See Appendices C, D, and E in attached document). From an adaptation perspective, each climate action’s effect on (1) sensitivity, (2) adaptive capacity, and (3) exposure to climate hazards was rated in seven key risk areas identified in the CCRA3:

• Risks to the viability and diversity of terrestrial and freshwater habitats and species from multiple hazards.
• Risks to soil health from increased flooding and drought.
• Risks to natural carbon stores and sequestration from multiple hazards leading to increased emissions.
• Risks to crops, livestock and commercial trees from multiple hazards.
• Risks to supply of food, goods and vital services due to climate-related collapse of supply chains and distribution networks.
• Risks to people and the economy from climate-related failure of the power system.
• Risks to human health, wellbeing and productivity from increased exposure to heat in homes and other buildings.
• Each of these three ratings was multiplied by the confidence rating (strength of evidence and level of agreement), without any weighting. This provides an overall rating of the action’s effect on each risk area, as outlined in further detail in the body of this report.

From a climate mitigation perspective, each climate action’s potential effect on (1) greenhouse gas emissions, (2) the rate of carbon uptake (carbon sequestration), and (3) the amount of carbon stored (carbon stocks) was assessed. Each of these three ratings were multiplied by the confidence rating, without any weighting.

Caveats

Due to the largely qualitative nature of the evidence base, assigning precise numerical values to the ratings was not feasible. For example, while it is theoretically possible to associate GHG emissions ratings with specific ranges (e.g., MtCO₂/year), the literature rarely provides such detail. Where estimates do exist, they are often highly caveated, context-dependent, and inconsistent. Furthermore, some actions lack sufficient definition—missing specific targets or measurable outcomes—making quantitative evaluation difficult.

Users are advised against summing individual ratings to produce an overall score for a climate action’s effect. This is particularly problematic for mitigation, where double counting may occur due to temporal dynamics (e.g., initial carbon sequestration followed by stock accumulation). For adaptation, a common metric would be required to enable aggregation, but such a metric does not currently exist and would be challenging to develop given the qualitative nature of most adaptation indicators.

Given the study’s focus on co-benefits and trade-offs, the direction of effect was prioritised over magnitude. This approach enabled identification of actions with relatively high co-benefits and minimal trade-offs, even where quantification was not possible.

Further refinement would be necessary to enable direct quantitative comparisons across actions. This could include:

1. Clearer specification of actions – Even where targets are defined (e.g., number of trees planted, heat pumps installed), outcomes vary depending on implementation details such as species, models, and location.
2. Development of a common metric – Where feasible, extracting quantitative estimates of change in a unified format would support comparison, contingent on clearer action definitions.

Finally, the study was constrained by time and focused only on the key risks identified in CCRA3. A broader set of risks was not considered, and future reassessments will be necessary as climate risks evolve.

Further research needs

While some actions were rated as having strong co-benefits and low or no trade-offs, these may vary over time. For example, while the action on “Suitable trees, crops, and livestock for future climate in appropriate locations” (CCRA3) has high co-benefits and no identified trade-offs, benefits for climate mitigation may only be delivered over time, especially regarding tree planting. In early stages a plantation may even lead to net carbon emissions, e.g., if planted on former pasture. Implementation of the action also needs to consider the increasing magnitude and frequency of extreme weather events as well as incremental climate change if it is not to lead to maladaptation.

This study has identified several areas where further research is needed to expand knowledge and improve understanding of the co-benefits and trade-offs between climate mitigation and adaptation in the UK. Such areas include:

1. Conducting syntheses of additional case studies to inform policymakers. These may regard other low/no-regret actions, climate actions with (limited) trade-offs, or climate actions with clear trade-offs.

2. Filling the remaining knowledge gaps regarding each of the climate actions and their outcomes for climate mitigation and adaptation.

4. Evaluating other co-benefits and trade-offs of climate actions. For instance, with respect to biodiversity and ecosystem services in the UK and elsewhere. In addition, further research could cover co-benefits and trade-offs between climate actions

3. Assessing the further 20 climate actions that were initially excluded (those identified from the UK Net Zero Strategy and the CCRA3).

5. Regarding the scope, scale and speed at which they might be implemented (e.g., nationally, locally, spatially).

Considering the eighth CCRA risk (i.e., multiple risks to the UK from climate change impacts overseas). This means observing interactions between climate adaptation and climate mitigation actions and outcomes in the UK and elsewhere.

Citation

Steller, R., Perring, M.P., Colonna, F., Clilverd, H., Fitch, A., Jones, L. and Smithers, R.J. 2024. Co-benefits and tradeoffs of UK climate actions. A systematic Rapid Evidence Assessment and rating of effects on climate adaptation and mitigation outcomes. Climate services for a net zero resilient world. UK Government.

This document is an output from the CS-NOW programme. CS N0W was commissioned by the UK Department for Energy Security and Net Zero (DESNZ), Climate Services for a Net Zero Resilient World (CS-N0W) is a four-year, £5 million research programme, that uses the latest scientific knowledge to inform UK climate policy and help the UK meet its global decarbonisation and resilience ambitions. CS-N0W enhances scientific understanding of climate impacts, decarbonisation and climate action, and improves accessibility to the UK’s climate data.

The programme is delivered by a consortium of world leading research institutions from across the UK, on behalf of DESNZ.