Transcript PHYSIS English V. - 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
Indicator species
Silent diversity
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 CORINEBiotopes inventory
of sites of European
Community
significance for nature
conservation was based
on species-oriented and
habitat-oriented criteria.
The latter resulted in a
larger number of
identified sites, in
particular, in regions of
diffuse distribution of
species.
Developments envisaged:
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.
Extension of the
continental frameworks to
other parts of the world.
Improvement of detailed
regional coverage of
existing continental
typologies.
Keys to habitat
Mapping of typology units.
identification at Investigation of scale
the regional level factors.
have been derived Validation of adequacy in
coverage of silent
from the Physis
biodiversity.
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.
www.naturalsciences.be/cb/