Jord Vand Luft Dyr og planter Grønland Samfund
  Udgivelser Overvågning Om DMU Viden for alle Nyheder
 
In English
 

Summary

This project is the first phase of a larger project with the overall aim to define specific conservation objectives for the marine Annex 1 habitats of the Habitats Directive. Eight of the marine Annex 1 habitats occur in Danish waters. Marine Natura 2000 sites where Annex 1 habitats are the reason or part of the reason for the designation cover 10,584 km2 or 74,7% of the total area covered by the Danish Natura 2000 network.

The report discusses the weaknesses of the definitions of the marine Annex 1 habitats. These habitats are defined primarily on the basis of geomorphology and not biology. Most (perhaps all) of the marine Annex 1 habitats encompass different biological communities. These should be defined or at least treated as separate habitats, each with their own set of indicators and thresholds. As a solution to this problem, it is proposed to divide the Annex 1 habitats into smaller often biologically founded units, called subfeatures.

The biological content of a habitat is governed by a large number of natural factors such as depth, illumination, salinity, distance to nutrient sources, bottom type, and exposure to wind and currents. Therefore, it can be difficult, if not impossible, to identify meaningful universally applicable biological indicators for assessing the conservation status of the Annex 1 habitats. The choice of indicators and their thresholds may, therefore, be applicable in certain water types only or even be sitespecific.

All marine habitats are negatively influenced by human activities, and assessments of Danish marine areas state that the quality of the ecosystems in general is not acceptable. A reduction of pressure from many of the anthropogenic pressure factors will have a positive effect on the structure and functioning of the Annex 1 habitats. Other pressure factors exist, like introduction of invasive nonindigenous species, which may result in irreversible negative impacts.

The development of a quality assessment system for marine Annex 1 habitats should, ideally, be based on knowledge of the habitats distribution, extent, structure, and functioning and of the occurrence of characteristic species in the absence of known anthropogenic pressure factors. However we face the problem that description of impact of pressure factors in scientific and other types of literature is a rather recent thing for Danish marine waters. The task - and the challenge - is to choose the levels of human impacts that can be accepted, if a favourable state of conservation is to be attained.

The development of a system for assessing conservation status for the marine Annex 1 habitats must take the following central aspects into account:

    · Annex 1 habitats should be subdivided into biologically meaningful units (subfeatures) in accordance with JNCC's proposal for Great Britain.

    · Knowledge of the distribution of the Annex 1 habitats and of their contents of biological based welldefined habitats is for Danish waters generally very poor. Considerable effort is needed to gather such knowledge. Until this has been done, the first step is to develop an assessment system for habitats or habitat subfeatures based on indicators and thresholds, that reflects the general quality of the site rather than specific communities of fauna and flora.

    · Most marine habitats have a depth dimension, which is central to the vegetation due to light extinction. The system of conservation objectives must take this important factor into account, perhaps by typological segregation.

    · Marked structuralising natural physical and chemical gradients through the inner Danish waters strongly influence biology. Typological segregation or sitespecific indicators and/or thresholds are, therefore, relevant.

    · Marine ecosystems are generally very dynamic. Knowledge of natural variations in controlling factors is essential for development of an assessment system for conservation status.

    · A baseline describing favourable condition of the Annex 1 habitats or habitat subfeatures can not solely be based on existing environmental conditions.

The important first step in developing a biological based system for assessing Annex 1 habitat conservation status is to achieve knowledge about the interaction between important pressure factors and the chosen indicators response to these pressure factors.

The chosen indicators must together be able to report on the condition of structure, function and characteristic species of the annex 1 habitat or subfeature in question and they shall function as tool to evaluate management of Natura 2000 sites in the future.

Knowledge about the relationships between indicators and pressure factors will be established using historic as well as recent data combined with empirical or dynamical modelling where possible. A satisfactory description of the relationships between pressure factors and attributes will be a powerful management tool. The tool will enable environmental managers to set thresholds for interest features and, thereby assess the condition of the feature.

If there is no sufficient data for scientific based thresholds, temporarily thresholds can be set based on expert judgement until proper data is available.

The ecological objectives of the EU Water Framework Directive are based on a different concept. This directive state that the objectives have to be defined based on knowledge of reference conditions. The reference condition is defined as pristine conditions with no or very minor human impacts. Despite of this difference between the two directives, it is very important to ensure the highest level of harmonisation between them.

The most important anthropogenic pressure factors have been identified for 7 of the 8 Annex 1 habitats present in Danish waters. Potential indicators have been identified and suggestions for methods to define their thresholds have been formulated.

The data evaluation indicates that a great amount of valuable data exists from Danish marine areas. However, dealing with specific habitat sites, this assessment also show that at present none or only sporadic data exists from many sites, making a judging of conservation status impossible in those cases.

The Danish regional and national environmental monitoring and mapping data have largely been collected according to standardised procedures since the 1980s. A large portion of the data is stored electronically. In spite of this, the process of attaining an overview of these data in connection with this project has been very time consuming, since the data were found in many different types of databases. Comprehensive analyses of data from the various Annex 1 habitats will entail some work gathering the data prior to analysing them.

The report also gives a proposal for guidelines for documenting the conservation objectives, to be described at a later stage of the process of developing a quality assessment tool for marine habitats.

Full report p1-61 in pdf. format (3001 KB)
Full report p62-96 in pdf. format (2930 KB)
0


Helle Thomsen

01.11.2007


DMU  | dmu@dmu.dk  

Box 358 | Frederiksborgvej 399 | 4000 Roskilde | T: 4630 1200

 CVR: 10859387

 EAN: 5798000867000