Ecosystem Accounts – Forests and Woodlands 2012-2022

Condition Accounts

Condition accounts record the condition of ecosystems in terms of selected characteristics at specific points in time. Over time, these accounts can be used to examine changes in condition, and provide information on the health and function of ecosystems and their capacity to provide ecosystem services.

For Forests & Woodlands, we have chosen two condition indicators to present in this initial set of accounts, Deadwood and Tree Cover Density. Deadwood represents an important resource for biodiversity, so including Deadwood as a measure of condition can give an indication of the health and functioning of the ecosystem. Tree Cover Density can vary depending on factors such as age of forest, timber harvesting, forest fires, or losses due to storm or disease. In general, higher Tree Cover Density is related to higher condition of Forests & Woodlands. Data for both of these indicators were compiled for the reference period (2012-2022), and are shown in Table 3.1. For Deadwood, an increase was seen between 2012 and 2022 of over 3m³/ha. Tree Cover Density increased from 51.4% to 58.6% between 2012 and 2018 (the latest year for which data were available).

When constructing condition accounts, it is useful to include reference level values to provide context to the variable values. By using reference level values, we can rescale the indicator values to between 0 and 1, where a value closer to 1 indicates better condition (see Background Notes for details). This allows us to see at a glance what the condition indicator is showing, and also allows us to compare different indicators. In this case, the indicator values for Deadwood increased from 0.38 to 0.60, a percentage change of over 55%. The indicator values for Tree Cover Density increased from 0.57 to 0.65, an increase of 14%. Using indicators like these can provide general information on the condition of an ecosystem and are important for tracking trends over time. Because just two indicators are used to represent all of the Forests & Woodlands in a country, however, they must be interpreted carefully and with an understanding of the limitations involved in using them in this way. This is a first attempt at examining the use of these indicators in the context of ecosystem condition accounts for Forests & Woodlands. Further development of condition accounts, to include additional biotic and abiotic indicators, will be undertaken by the CSO to develop a condition index which can be used in the future to track changes in the condition of Forests & Woodlands. 

Deadwood

The National Forest Inventories provide detailed information not only on the overall amount of Deadwood, but on the types of Deadwood and the types of forests in which it occurs. The total volume of Deadwood in Forests & Woodlands increased from 7 million m³ in 2012 to 10.175 million m³ in 2022. Figure 3.1, Table 3.2. 

Tree Cover Density

Overall, the Tree Cover Density of Forests & Woodlands increased from 51.4% to 58.6% between 2012 and 2018. In general, higher Tree Cover Density can be associated with better condition, as events resulting in reduced tree coverage such as timber harvesting, forest fires, or losses of trees due to storm or disease have a negative impact on the condition of the forest. Increases were seen in all types of forest, with the exception of Transitional forests. Broadleaved forests had an increase of around 47%, from 39.6% to 58.2%, Coniferous forests increased by about 11%, from 53.7% to 59.5%, and Mixed forests increased by around 31%, from 51.6% to 67.7%. For Broadleaved, Coniferous, and Mixed forests the Tree Cover Density of the Immature forests (i.e. those which were established in the previous six years) was much lower than the Mature forests. The Tree Cover Density of Transitional forests decreased by just over half, from 37.3% to 16.2%. Figure 3.2, Table 3.3. Note that the 2018 data were at a higher resolution than the previous years which may impact these results.