openNCAI

openNCAI - R package to calculate a natural capital assets index

openNCAI is an R package which I developed with the support of Chris Littleboy as part of the FORTH2O Policy Innovation Partnership project at the University of Stirling. It calculates a regional natural capital assets index (NCAI) following the method designed by NatureScot to calculate Scotland's NCAI. openNCAI can be installed from CRAN [in R, run: install.packages("openNCAI")] and the code is available on GitHub, here.

What is a natural capital assets index?

A natural capital assets index is a statistical tool for tracking the capacity of a region's natural habitats to provide the ecosystem services needed for the population to survive and thrive. Natural habitats are areas where people and things live, e.g. forests, heathlands, lochs and rivers. Ecosystem services are outputs from these habitats which we rely on, e.g. food, fuel and materials, things like flood control and pollination which keep the ecosystem working, and cultural contributions like places and wildlife which we enjoy. We expect this capacity to change based on how much habitat there is and the condition it is in.

To estimate capacity, the NCAI process uses a complex calculation to combine information about the extent and condition of natural habitats at a particular point in time, with weightings decided by experts. The output is a single numeric (non-monetary) value, the indicator, set to 100 in year one. Calculating proportional changes in this indicator over the years generates the index, which allows us to see how capacity is changing over time. 

The aim is to summarise a lot of information in a single variable which can be tracked to monitor changes and inform and evaluate policy decisions. For example, below is a graph of Scotland's NCAI over the years 2000-2022, reproduced using Scottish Government data and openNCAI. This is the most simple representation, but the index can be decomposed to assess how, for example, changes in different habitats or different ecosystem service outputs contribute to this trend.

Why write openNCAI?

Scotland's NCAI was originally calculated using a spreadsheet. While this method is robust and records exactly how the calculation happens, it can be easy to make errors in a spreadsheet, and cumbersome to make changes to the process or input data. By recreating the process in R, we make it easy to change the inputs, so we can do things like:

• Calculate an NCAI for a different region, e.g., at FORTH2O we are interested in calculating the statistic for the Forth River Basin area where we are doing research to support better policy action around water,

• Update any part of the process as we learn new things, e.g., what if new information and a changing world means that we now believe flood control is more critical to survival than before?

• Carry out sensitvity analysis, e.g., find out how much the index would change if we measured something differently.

Because openNCAI is open source - meaning anyone can see, reproduce, or customise the code - it also makes it easy for the Scottish Government or any other user to communicate openly their exact calculation method. NatureScot's underlying method uses several established European or international classification schemes, so if a neighbouring country or region wanted to build their own NCAI, there is likely to be a lot of shared relevance. The weights and metadata which underpin the Scottish calculation are bundled with the openNCAI package to provide a helpful starting point. 

Learn more

You can find out more, take and use the code, and contribute to development by visiting the openNCAI GitHub repository. Start here:

openNCAI  - READ ME

The diagram below gives an idea of how the calculation happens and what data is required.