Transcript Physis - Conservation Biology Section

HABITAT TYPOLOGIES AND CONSERVATION OF BIODIVERSITY
Pierre Devillers, Jean Devillers-Terschuren and Roseline C. Beudels-Jamar
Royal Belgian Institute of Natural Sciences, Conservation Biology
The principal mechanism that drives the biodiversity crisis, threatening species, populations and biocoenoses, is habitat destruction, fragmentation and degradation. The establishment of
coherent networks of areas under diverse levels of protection is the most adequate corrective measure and at the core of conservation strategies. Adapted to the conservation of the biological
values targeted, these networks are usually capable of preserving most species and the communities they constitute. Overall conservation measures applied in the rest of the environment bring
a complement of protection to less sensitive species and less fragile communities.
The individual sites that compose the networks are chosen for their contribution to the overall diversity of the system, to the complex requirements of a species or a community, or to the
representation of the spectrum of their geographical and ecological variation. Some sites are established for the preservation of threatened or patrimonial species, with requirements that
exceed those of most members of the communities to which they belong. For these sites, data about the target species are, and will remain, the best source of criteria for site selection. Other
sites, perhaps a majority, should be dedicated to the conservation of the entire regional diversity. The definition of criteria for their selection is a central preoccupation of conservation biology.
The total diversity of species, populations and interactions cannot be accurately inventoried, even less included in legislation. Resorting to surrogate variables is thus inescapable.
Traditionally, surrogates have been indicator species or groups of species. Although this approach, illustrated, in particular, by the hotspot methodology, has had undeniable successes. It has,
however, shown its limitations. At the small scales of spatial resolution characteristic of conservation areas world-wide, networks established for distinct taxonomic groups are not congruent.
It appears that a methodology based on the recognition of a sufficiently detailed array of habitat units offers an operational alternative. The holistic approach that it constitutes insures a less
uncertain link between the units taken into consideration and their constituting elements than that which might exist between two unrelated taxonomic groups. At the same time, the
integration effect of these units permits the consideration of a much smaller list of entities than the full array of species that contribute to their construction.
Species lists
Target species
Species-oriented
conservation areas
Hotspot conservation
Silent diversity
Indicator species
Flagship species
Surrogate indicators
Habitat lists
Target communities
Habitat typologies
Habitat-oriented
conservation areas
The Physis typology, derived from the methodology developed for the CORINE-Biotopes project, provides a framework to organise in an ordered sequence the habitats of the world.
Within its scheme a habitat is a three-dimensional spatial entity that comprises at least one interface between air, water and ground spaces and includes both the physical environment and
the communities of plants and animals that occupy it. Habitat definitions depends on the scale at which they are considered. The level of resolution of the Physis typology is that of the
ecological requirements of small vertebrates, large invertebrates and vascular plants.
A unit in the Physis habitat typology is a habitat type, thus a characterisation of a collection of spatial entities sufficiently alike in abiotic conditions, physiognomy, composition of plant
and animal communities to play similar roles from the point of view of nature conservation. There is an unavoidable degree of arbitrariness in deciding whether two communities are
sufficiently similar to be referred to the same unit, or conversely, sufficiently different to warrant distinctive treatment. For plant communities, phytosociological criteria were used to
assess degree of divergence and its relevance to sensitive species. For animal communities, data are often lacking precisely for the groups most in need of habitat conservation rather than
species-specific programmes.
All habitat classifications use, alone or in combination, similarities in physiognomy, abiotic conditions, plant community composition, plant dominance, plant community succession and,
sometimes, animal community composition to combine elementary units into collective entities of successively higher rank. The priority given to the various criteria and the ensuing
classifications are necessarily a matter of choice. The guideline of the Physis habitat classification has been to use large-feature physiognomy, plant-community composition and
biogeographical or ecological factors underpinning animal-community composition, in that order. The scheme allows for evolution of the hierarchy as understanding of the habitats of a
geographical area improves, as new needs of identification arise, as an increasing portion of the total geographical area concerned is examined in detail without affecting previous
applications of the list.
The method has, so far, been applied to three biogeographical realms. It has resulted in the constitution of three databases, accompanied by a number of satellites and excerpts :
A classification of Palaearctic habitats
Habitats of South America
Habitats of Africa
The Physis habitat typology, and its predecessor, the CORINE-Biotopes habitat typology, have had a number of
applications, at continental, regional and local scales. Among them:
The CORINE-Biotopes inventory of sites
of European Community significance for
nature conservation was based on speciesoriented and habitat-oriented criteria. The
latter resulted in a larger number of
identified sites, in particular, in regions of
diffuse distribution of species.
Council Directive 92/43/EEC of the
European Union on the conservation of
natural habitats and of wild fauna and
flora. Appendix 1, listing habitats to be
included in the Natura 2000 Network was
constructed on the basis of the CORINEBiotopes typology.
Annex I. Natural habitat types of
community interest whose
conservation requires the
designation of special areas of
conservation Interpretation Code:
The hierarchical classification of
habitats produced through the Corine
programme (Corine biotopes project) is
the reference work for this Annex. Most
types of natural habitat quoted are
accompanied by the corresponding
Corine code.
The Physis typology was directly instrumental
in establishing a list of priority habitats for the
Bern Convention. It is one of the tools of
construction of the Emerald Network of sites
being identified throughout Europe at the
initiative of the Council of Europe.
Keys to habitat identification at
the regional level have been
derived from the Physis typology,
in particular, in the Walloon
Region of Belgium.
Clé d'identification provisoire des
habitats de la Région wallonne
La clé est formée d'une série de tableaux.
Chaque tableau offre un choix multiple
dont les options correspondent à des
cases. Dans chaque case se trouve un
texte d'aide au choix, une borne
d'information et une borne de sortie.
Developments envisaged:
Extension of the continental
frameworks to other parts of
the world.
Improvement of detailed
regional coverage of existing
continental typologies.
Mapping of typology units.
Investigation of scale factors.
Validation of adequacy in
coverage of silent biodiversity.
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