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Approach, reliability and working with figures in the Nature Data Compendium

Indicator selection


The indicators have been selected in such a way that, taken together, they provide a picture of the main developments in nature and landscape. Furthermore, attention has been paid to safeguarding reliability and to possible periodical updates, especially of time series. The main focus in this respect is on national developments and developments in ecosystems such as dunes or forests. Local figures are provided on occasion as examples.

Information by indicator


Examples of indicators are the species included in species protection plans or species protected pursuant to the European Habitats Directive. Other examples are types of flora or fauna that express major developments in ecosystems. The indicators also look at the extent to which the objectives of the nature policy have been achieved. Generally speaking, each indicator deals with developments over time, the causes of the developments and technical explanations of the accompanying graph, table or map.

Index figures for species


Numbers for individuals of animals or plant species are either not available or inaccurate in many cases and it is only possible to provide an indication of developments over time using index figures. Index figures are determined by taking the numbers measured in a particular reference year as 100 and then stating the numbers for the other years as a percentage compared to the base year. Many reference figures are calculated using special statistical software that can take into account all sorts of complications, such as areas where sampling is inadequate, serial correlation and missing counts (Pannekoek and Van Strien, 2001).

The base year for a number of indicators is 1990 or the first year after that for which figures are available. In isolated cases, it was necessary to adopt a later year as the base year, especially in the case of species new to the Netherlands. However, in order to make a better assessment of recent trends, it makes sense to look at the figures in a historical context. When suitable information was available, 1950 was adopted as the base year. In some cases even, 1900 or earlier is the base year. These historical figures consist of estimates based on research conducted for the development of indicators.

Targets


Policy targets are mainly discussed in the 'Nature Policy' section and are derived from the relevant policy memorandums. The memorandum consulted was usually 'Natuur voor mensen, mensen voor natuur' (Nature for people, people for nature). Where this was not possible because the targets had not yet been sufficiently elaborated, other policy documents were used, in particular the Structuurschema Groene Ruimte (Structure Plan for Green Space). Targets are also derived from other relevant government decisions about nature and landscape. Examples are the agreements about ICES investments and the Belvedere memorandum. The various indicators describe how the targets are determined and which policy documents are used.

Indices


In addition to figures about separate species, aggregate indicators are also used. They are referred to as Indices. They bring together developments in many separate species, making the information more understandable. The indices used are the Soortgroep Trend Indexen (Taxonomic Group Trend Indices - STI) and the Natural Capital Index v(NPB, 2001; Ten Brink et al. 2001). More Indices will be included in the future, both for nature conservation and for the perception and use of nature and landscape.

Taxonomic Group Trend Index


The Taxonomic Group Trend Index (STI) is the average annual index figure for all individual species of a particular group, for example dune butterflies or meadow birds. The index figures for these species are geometrically averaged, with the underlying idea that the halving of the index for one species from year to year is, in a sense, equivalent to the doubling of the index for another species. The geometrical mean of the index figures 50 and 200 is 100. The figure below provides an example of this process. A different calculation method is used for the Natural Capital Index.

Reliability


The amount of data used must be adequate. In other words, it has to be sensitive enough and free of distortion. It is necessary to exclude artefacts resulting from the methods used or observational bias (see also: Van Strien and Van der Meij, 2002). The trends for species are appraised statistically. Where the text refers to falls or increases, they are statistically significant.

In each indicator, the organisations that provide the data are listed at the bottom left of the relevant table or figure. Furthermore, the reader is referred to publications in which the approach adopted is explained in greater detail.

Statistics Netherlands, the Netherlands Environmental Assessment Agency of the RIVM (MNP) and the Agricultural Research Service (DLO) are responsible for the reliability of the indicators. On the website, the body or bodies responsible for the indicator are listed at the bottom right of the figures or tables.

Improvements are possible in the quality of some indicators. That is the case, for example, for the indicators relating to surface data for ecosystems. Here, more coordination is required for the various sources, with their differing approaches to classification.

Data provision


Many indicators for terrestrial ecosystems are based on data from the Netwerk Ecologische Monitoring (Ecological Monitoring Network - NEM). The NEM is an alliance involving a range of organisations (EC-LNV, RIVM, CBS, RIKZ and RIZA) for the purposes of the development and maintenance of nature monitoring networks. The monitoring networks of the private data management organisations are included in the NEM. Data from provincial authorities about meadow birds and higher plants are also used for the NEM. In the NEM, Statistics Netherlands is responsible for producing reliable results from the basic data provided by the terrestrial monitoring networks.

The data about water systems are provided mainly by the National Institute for Coastal and Marine Management (RIKZ) and the Institute for Inland Water Management and Wastewater Treatment (RIZA). The information about support and about the effect of the policy comes from a wide variety of sources. The structural arrangements for the supply of data from these sources are still limited. The Nature Data Compendium makes it possible to organise the data supply on more structured lines.

A lot of information about policy progress comes from the Dienst Landelijk Gebied (Government Service for Land and Water Management - DLG). This is mainly information about the progress of policy as described in the Structuurschema Groene Ruimte (Structure Plan for Green Space). Most of this information is therefore about land acquisition, nature organisation and green projects. Some of the information required for policy evaluation is collected by the Netherlands Environmental Assessment Agency itself, for example the information about the progress made with area plans by provincial authorities. The supply of information about the progress of policy is far from perfect. The DLG is working on improvements in data gathering and reporting. LASER, a section of the Ministry of Agriculture, Nature and Food Quality, still has a lot of work to do before the supply of information relating to the Management Programme is up to scratch.

References


  • Bisseling, C., A. van Strien and M. de Heer (1999). Weten wat er leeft. Ecologische monitoring voor het rijksbeleid. Eindrapport Netwerk Ecologische Monitoring. IKC-Natuurbeheer, Wageningen.
  • Brink, B.J. ten, A. van Strien and R. Reijnen (2001). De natuur de maat genomen in vier graadmeters. Landschap, (18) 1: 5-20.
  • CBS and RIVM (2001). Environmental Data Compendium. Kluwer, Alphen aan den Rijn.
  • LNV (1995). Structuurschema Groene Ruimte: het landelijk gebied de moeite waard. Deel 4: Planologische Kernbeslissing. Ministry of Agriculture, Nature Management and Fisheries, The Hague.
  • LNV (2000). 'Natuur voor mensen, mensen voor natuur'. Nota natuur, bos en landschap in de 21ste eeuw. Ministry of Agriculture, Nature Management and Fisheries, The Hague.
  • NPB (2001). Hoe gaat het met de natuur? Nature Planning Bureau, Bilthoven.
  • RIVM (2002). Natuurbalans 2002. Kluwer, Alphen aan den Rijn.
  • Pannekoek, J. and A.J. van Strien (2001). TRIM 3 Manual. Trends and indices for monitoring data. Research paper 0102. Statistics Netherlands, Voorburg/Heerlen.
  • Strien, A.J. van and T. van der Meij (2002). Landelijke natuurmeetnetten in 2001. Resultaten en ontwikkelingen. Statistics Netherlands, Voorburg/Heerlen.