Ontology

The classification of habitats has played an important role in understanding ecological systems at scale and informing policymakers and regulations. There are multiple ways of classifying habitats and we decided to explore some of them to include a comprehensive view of the sampling sites of MfD.

Natura 2000

The Council Directive 92/43/EEC (approved by the European Commission on 21 May 1992) on the conservation of natural habitats and wild fauna and flora, specifically Annex I, lays the foundation for habitat and species preservation.

To classify habitats, a four-digit code system is utilized. The general scheme follows the pattern X-X-XX, where the fourth digit is often subordinate to the third. However, in the case of "Temperate heat and scrub" (4XXX), the second digit is disregarded.

In addition, an interpretation manual accompanies the system, providing valuable lists of discriminant plant species. These resources aid in accurate identification and differentiation, supporting efforts to conserve and protect natural habitats and the diverse wildlife they support.

Example: 1210 Annual vegetation of drift lines

The chosen example habitat is identified by the code 1210. This means that, following the hierarchy of Natura 2000 (extract below on the left), the habitat belongs to:

• 1-X-XX: Costal and halophytic habitats
• 1-2-XX: Sea cliffs and shingle or stony beaches
• 1-2-10: Annual vegetation of drift lines

Checking the manual (extract below on the right) it is possible to retrieve the description of the habitat (point 1), as well as a list of characteristic plant species (point 3).

EUNIS

The EUNIS information system plays a vital role in supporting the implementation of the Biodiversity Strategy for 2030 by contributing to the knowledge base.

It employs a unique naming convention, with a variable number of characters, to classify biodiversity-related information. Each term begins with one of seven letters that designate the general "category" and is followed by up to seven characters, indicating the depth of knowledge within the ontology.

In addition, the system provides an interpretation manual that includes lists of discriminant plant species, facilitating accurate identification and differentiation.

Moreover, it features a map showcasing Natura 2000 sites and the Red List, enabling visual representation of crucial conservation areas and endangered species. Overall, the EUNIS information system combines classification, an interpretation manual, and a map, providing valuable resources for biodiversity research and conservation efforts.

Example: N11 Atlantic, Baltic and Arctic sand beach

The selected habitat is associated to the code N11, and, similarly to Natura 2000, it is possible to obtain an increasingly precise level of characterization:

• N-X-X: Coastal habitats
• N-1-X: Coastal dunes and sandy shores
• N-1-1: Atlantic, Baltic and Arctic sand beach

In the same file it is possible to obtain info about the diagnostic, constant and dominant species in the habitat (extract below).

Custom MfD ontology

The custom MfD ontology is an extension of the Natura 2000 classification where we mostly acted in two ways:

• Slightly modifying the existing classification (i.e., creating a second level to the 4XXX division);
• Adding completely absent categories (i.e., the man-made environments)

Match across ontologies

The EUNIS tables provided by the European Environment Agency contain also links to other classification systems, e.g., Natura 2000.

The image on the right depicts the EUNIS (on the left side) and the Natura 2000 (on the left) classification systems as trees. The trees were rooted for plotting purposes and in the Natura 2000 the 2nd digit of the 4XXX series (0) was treated as a proper second level. The EUNIS classification was truncated the third level (which has a comparable size to the one of Natura 2000), because the matches with other ontologies were reported only at this level. The grey links are the matches between entries of the two systems. The majority of the relationships (61.3% and 65.1% to EUNIS and Natura 2000, respectively), are one-on-one. There are two extreme cases in which EUNIS gather 12 habitats of the Natura 2000 system: T17 and T19. Both those cases are forests and have a wealth of subcategories in the EUNIS classification.

An important advantage of the the EUNIS classification is that it contains a man-made habitat category (highlighted in blue in the image on the right) conversely to the Natura 2000.

Example: Natura 2000's 1210 vs. EUNIS' N11

The Natura 2000 class 1210 Annual vegetation of drift lines corresponds to four matches in the EUNIS ontology. These matches include:

• N11 Atlantic, Baltic, and Arctic sand beach;
• N12 Mediterranean and Black Sea sand beach;
• N21 Atlantic, Baltic, and Arctic coastal shingle beach. and
• N22 Mediterranean and Black Sea coastal shingle beach.

The EUNIS ontology incorporates more geographical context, resulting in the possibility to prune the matches (i.e. Denmark is among the regions listed in N11 and N21). To further prune the habitat choice, sampling pictures can be utilized, distinguishing between shingle and sand.