# openNCAI #

openNCAI is an R package for calculating a regional natural capital assets index (NCAI), using the method designed by NatureScot to calculate <a href = "https://www.nature.scot/professional-advice/social-and-economic-benefits-nature/natural-capital/scotlands-natural-capital-asset-index">Scotland's NCAI</a>. It uses habitat extent and condition data, along with metadata and systems of weights, and produces a yearly single figure indexed around a year one value of 100. Further decompositions of this figure, for example by habitat or ecosystem service type, may be output on request, along with intermediate steps in the calculation. 

### Installation ###

Install the released version from CRAN using:

`install.packages("openNCAI")`

Or the development version from GitHub using:

`install.packages("devtools")`

`devtools::install_github("oharakate/openNCAI", build_vignettes = TRUE)`

Note that `build_vignettes = TRUE` is recommended in order to access all documentation. 

### Further Information ###

The calculation of the NCAI is based on the following core measurable or estimable quantities and concepts:

| Concept | Explanation |
| :--- | :--- |
| **Natural habitat** | Natural habitats are areas where flora and fauna live. In economic terms, measurements of the **extent** (how much) and **condition** (how healthy) of natural habitats represent **stock**. |
| **Ecosystem service** | Functions performed by natural habitats which support our ecosystem. These might be providing food or fuel, cleaning the air, contributing to our culture. The index estimates **flow** of ecosystem services from our **stock** of natural capital, weighting by **importance** to our economy and community. |
| **Provision per unit** | The notional capacity of a natural habitat to provide an ecosystem service. E.g., one hectare of market garden has the potential to provide more food than one hectare of cultivated garden in a public park. |
| **Importance** | The relative demand for and importance of any ecosystem service to our community and economy. E.g. having drinking water is likely to be more essential to survival and well-being than rearing animals to pull carts and ploughs. |
| **Flow** | The actual rate of delivery of ecosystem services from a natural habitat, estimated based on the current *condition* of a natural habitat. E.g. while a cornfield offers good **provision per unit** in contributing to the service of providing food from plants, the **flow** of that service could be reduced if poor weather meant the crop did not grow well. In calculating NCAI, data from a variety of sources are used as indicators of the condition of habitats and the subsequent likely flow of ecosystem services. |
| **Natural capital assets** | A representative figure (non-monetary) to track the capacity of the available natural habitats to provide ecosystem services. |

openNCAI uses the method design by NatureScot to calculate Scotland's NCAI (McKenna et al, 2019, Albon et al 2014). It generates an estimated assets valuation by weighting the extent of natural habitats by their provision per unit of services, demand for different services, and the likely flow of services based on the condition of the habitats. 

Calculation relies on three types of information. These are:

1. Environmental measurements of the extent and condition of natural habitats – updated yearly (as available),
2. Lists of habitats in Scotland and the ecosystem services they provide – decided by expert opinion at the beginning of the process,
3. Weighting schemes which denote importance of ecosystem services, the potential of habitats to provide them, and the relevance and salience of habitat condition indicators in representing flow of services from habitats – decided by expert opinion at the beginning of the process.

The following diagram outlines the calculation process:

![openNCAI calculation process](https://github.com/oharakate/openNCAI/blob/master/man/figures/ncai_calculation_process.png)

# References #

McKenna, T. et al. (2019) “Scotland’s natural capital asset index: Tracking nature’s contribution to national wellbeing,” Ecological Indicators, 107, p. 105645. Available at: https://doi.org/10.1016/J.ECOLIND.2019.105645.

Albon et al. (2014) “SNH Commissioned Report 751: A systematic evaluation of Scotland’s Natural Capital Asset Index.” Available at https://www.nature.scot/sites/default/files/2025-06/naturescot-commissioned-report-751.pdf .
