Biological diversity can be measured using a set of indicators.

In several workshops at the beginning of the project, data and information requirements were determined by consulting future BDM users in order to use the funds in the most efficient way possible. In addition, it was necessary to consider the needs of the international organizations (such as the OECD – the Organization for Economic Cooperation and Development) to which Switzerland has to provide data.

Since the PSR model is frequently used in international monitoring programs, Switzerland also decided to adopt this model. The acronym PSR stands for “pressure-state-response”; this model was developed by the OECD.

The PSR model measures biodiversity by using indicators. It works with three different types of indicators:

• State indicators are the most important biodiversity indicators. They indicate the most important changes in biodiversity, and include the different levels of species diversity as well as genetic and landscape diversity. One important indicator, for example, describes the change in the number of mammals living in the wild in Switzerland.

• Pressure indicators describe the different factors that affect species diversity. These indicators can include factors such as the food supply, the structure of a habitat or land-use technology. The range of pressure indicators is very broad.

• Response indicators measure trends and developments that contribute to maintaining biodiversity such as the change in the total area of organic farms.

Determining species diversity Species diversity is surveyed in the field. In addition, the BDM programme also measures influences on biodiversity such as the use of fertilizer or the size of protected areas.