The UK Government is committed to sustainable development, but this broad concept provides little guidance to decision-makers facing difficult trade-offs.

To assess the impacts of our actions, we need to understand how the ‘stock’ of natural capital will continue to produce the ‘flow’ of ecosystem (and other) services over time. However, we lack a systematic method to assess this resilience and feed it into policy and decisions.

The intention of a NCAC is to support such decisions by providing advice on: when, where and how natural capital assets are being used unsustainably; where action to protect and improve natural capital should be focussed for greatest impact on well-being; and, the research priorities that follow from these needs.

A NCAC analyses what society wants from natural capital – i.e. its performance. Its purpose is to inform decision makers about how changes in a natural capital asset affect human wellbeing.

As productivity of natural capital can have opportunity costs, optimal performance is not usually maximum performance. Policy targets (e.g. for maximum sustainable yield or maximum economic yield of fish stocks; carbon concentrations that avoid dangerous climate change; nature conservation targets) give indications of desired performance, but these can be conflicting and/or ambiguous.

Ecosystem services are embedded in the tool: NCAC provides a way of organising available evidence to give insights into thresholds and trade-offs by incorporating concepts of integrity, performance, red flags and sustainability. These need to be effectively understood if we are to manage natural capital optimally for society’s long-term needs. Data on exactly where thresholds are is rarely available to inform decision-making, but observations of different examples of natural capital management can provide data on systems that are above and below thresholds (e.g. healthy and collapsed fish stocks).

The consequences of crossing thresholds depend on environmental factors (e.g. speed with which productivity will recover) and economic factors (e.g. value of goods and services produced and substitutes available).

The information a NCAC provides will be possibly most useful at strategic decision-making points, but can input in a variety of ways to:

• scope knowledge of an issue and understanding (can we answer the questions about sustainability?)
• analyse specific ecosystem services/capital relationship (e.g. pollination)
• analyse a discrete local site (e.g. large estuary)
• build a picture of complex choices on natural capital: in which case a number of iterations of analysis may be needed, starting with a large scale NCAC (like the majority of those in this project), from which critical areas of capital are identified. These could then be subject to further analysis of where capital is at risk of being used unsustainably, and these results could be fed back into the larger scale NCAC.

The uplands case study focused on the productivity of upland soils on regulating ecosystem services in order to make the analysis manageable. Clearly an analysis of all productivity from the natural capital of the uplands of England and Wales (which is a large scale and very varied piece of capital) would be a substantial undertaking, akin to a Government evidence review. Even if sufficient resources were available for such a review, it is unclear if a NCAC is manageable at such a scale in theoretical terms. For example, the complexity of synergies and trade-offs between services may render either analysis impractical or too generalised to give real insights.

The case study considered a peatland soil, which underpins the production of carbon regulation, water regulation and biodiversity services from various upland habitats. These habitats rely on peatland soils (as a natural capital asset) in combination with other natural capital assets in order to produce these final ecosystem services. The productivity of each of these services is a function of peatland soil extent and condition and other factors. Therefore it could be deemed to be a ‘flagship’ natural asset that reflects the integrity of the natural assets that combine to be productive.