Natural capital is the environmental resources (e.g. plants, animals, air, water, soils) that combine to yield a flow of benefits to people. When the Natural Capital Asset Index (NCAI) was launched in 2011, Scotland became the first country in the world to publish such a detailed attempt to monitor annual changes in its natural capital. It was reviewed by experts in 2014, and has since been revised. The NCAI is a work in progress and efforts will continue to refine its methodology and data.
Source of Data:
The NCAI monitors the quality and quantity of terrestrial habitats in Scotland, according to their potential to deliver ecosystem services now and into the future. It is a composite index, based (i.e. equal to 100) in the year 2000. The latest NCAI publication can be found here: https://www.nature.scot/scotlands-natural-capital-asset-index-0.
An evaluation of the NCAI was conducted by experts from the James Hutton Institute (JHI) in 2014 which identified¬†issues with some of the 100 indicators included in the index as well as the methodology used to calculate the NCAI. The full report of the evaluation, which includes a detailed section on the methodology that was used to calculate the index, can be found here: https://www.researchgate.net/publication/319807862_A_systematic_evaluation_of_Scotland's_Natural_Capital_Asset_Index.
NatureScot have since taken steps to revise the methodology used to calculate the NCAI. The European Nature Information System (EUNIS) land cover classification is now used, while previous versions of the index used the Broad Habitat classifications. The following Scottish habitats are included in the NCAI:
Inland surface waters
Raised and blanket bogs
Woodland and forest
Unvegetated or sparsely vegetated
Please note that Marine habitats are not included in the NCAI, a feasibility study into whether they can be included in the future was carried out in 2019.
The first stage of the NCAI‚Äôs revised methodology involves an evaluation of each habitat‚Äôs potential, if in good condition, to deliver the range of ecosystem services for Scotland. Each ecosystem service is also assessed to estimate its relative contribution to human well-being.
The second stage involves the use of a number of indicators to monitor change in the quality of our habitats (in terms of ability to deliver ecosystem services). An ‚Äėideal‚Äô indicator is available since at least 2000, is updated regularly and is correlated with natural capital. However, in some instances data availability has been limited and imperfect proxies have been used.
A full methodology of the NCAI, with reference to the research it is based upon can be found in the journal article published in Ecological Indicators: McKenna et al, 2019.
Natural capital: the environmental resources (e.g. plants, animals, air, water, soils) that combine to yield a flow of benefits to people.
The 2015 NCAI includes an updated classification for ecosystem services1 and habitats2, which improves the validity of the NCAI and is standardised with other work in Scotland and Europe.
2 European Nature Information System (EUNIS). See SNH CR766 for more detail.
Criteria for Change:
This evaluation is based on comparing the most recent index value to the index value from three years previous. Any difference within¬†2 percentage points suggests that the position is more likely to be maintaining than showing any change. An increase of¬†2 percentage points or more suggests the position is improving; whereas a decrease of¬†2 percentage points or more suggests the position is worsening.
For information on general methodological approach, please click here.
The NCAI measures the quality and quantity of habitats in Scotland, according to their potential to deliver different ecosystem services now and into the future. Ecosystem services can be categorised as follows:
For example: grass for livestock; dairy products; timber; soft fruits such as raspberries; wild salmon and venison; freshwater for drinking and whisky production.
Regulation and maintenance services
For example: climate regulation via carbon storage in peatlands; natural flood protection from bogs and woodland; pollination of crops; habitats for wildlife.
For example: watching wildlife; recreational fishing; symbolic species and landscapes; information for education.
An index is calculated for each of the three categories of ecosystem services. These indices are then combined to give the overall index, applying a weighting according to their relative importance. Regulation and Maintenance services has a weighting of 0.5 applied and Provisioning and Cultural services each have a weighting of 0.25 applied.
The Ecosystem Health Indicators (EHI) for Scotland are also being developed in partnership with NatureScot to assess progress towards achieving the 2020 Challenge for Scotland‚Äôs Biodiversity outcome "increasing our stock of natural capital for the next generation". The EHI operate across multiple scales ‚Äď from national down to more local levels, such as the sub-basin areas used for river basin management planning. In the future, when both the EHI and NCAI are further developed, it may be possible to link the NCAI to the EHI to give a more in depth analysis.
Future issues or reviews:
The NCAI will continue to be developed, with the next data collection update due in March 2023.
Due to changes in the methodology of some of the underlying biodiversity data some historical headline values of the NCAI have changed slightly, although the general trends remain the same.
Some of the data for this update was impacted by limitations to field work due to the COVID-19 pandemic.