IN NATURAL ENVIRONMENTS
by species richness, density, and diversity.
Unit of measure
Number of species
(or selected taxa) and their variations.
2. Position within the
logical framework DPSIR
Type of Indicator
3. Target and political
indirectly contributes to define biodiversity measured
by species richness, density, and diversity in natural
environments threatened by desertification.
with respect to desertification
UN Convention to Combat Desertification (1995) defines
desertification as "land degradation in arid, semi-arid
and dry sub-humid areas resulting from various factors,
including climatic variations and human activities."
These vulnerable drylands comprise about 40% of global
lands, of which at least a quarter are already degraded.
It is generally agreed that desertification most frequently
results from development which is not sustainable, due
to the mismanagement of biodiversity: overexploitation
of vegetation cover leading to topsoil erosion and hence
reduced productivity, or improper water use resulting
in salinization. This affects not only crops but also
rangeland and its biodiversity. When the transformation
of rangeland to irrigated cropland results in desertification,
the effect on biodiversity is in the loss of natural
ecosystems. When the overexploitation of rangeland results
in desertification, the effects on biodiversity are
first expressed in the direct loss of plant species
and the animals associated with them, and later in the
loss of topsoil and the potential for rehabilitating
biodiversity. These biodiversity losses, both in goods
and services, further exacerbate desertification in
the affected areas. They also affect adjacent and other
areas, which used to enjoy some of the services, such
as aquifer recharge for example. Biodiversity conservation
and sustainable use of biological resources can hardly
be achieved in arid and semi-arid areas without taking
into account the underlying causes of desertification,
which affects all natural resources. Similarly, desertification
control activities and restoration processes in these
areas should include wetlands conservation as a priority.
Finally, availability of water resources in arid lands
depends directly on the rainfall (and climate variations).
Hence, the links between biodiversity, desertification,
wetlands and climate change are part of the day-to-day
life of millions of people living in the drylands.
Conventions and agreements
The loss of biodiversity
often reduces the stability of ecosystems, reducing
their ability to provide goods and services that sustain
human life. The protection of biodiversity is therefore
in mankind's self-interest and has been recognized
as a major aspect of sustainable development through
the adoption of the Convention on Biological Diversity
at the 1992 Earth Summit in Rio de Janeiro. The UNCCD
recognised the particular conditions of the Mediterranean
where the causes of desertification include the extensive
forest coverage losses due to deforestation, frequent
wildfires, intensive grazing etc. (Convention text
as of September 1994 and as of September 2001).
of the indicator
This is a fundamental
indicator of the impact of degradation of the forest
surface and, in general, of natural environments.
Information about desertification can help in addressing
political measures to recognise the loss of biodiversity
an area and to organise efficient control, and indirectly
to reduce desertification.
4. Methodological description
and basic definitions
is defined as the total number of species in an area
measured by a standard protocol. It is one of the
common measures for biodiversity which can be assessed
on three levels: the species, the genetic and the
ecosystem level. Species richness refers to the species
level (plants, animals and micro-organisms). The assessment
of species richness of an area should not be confused
with species diversity measurements that include components
of both species richness and the evenness or dominance
among the species present. The assessment of species
richness is closely related to the process of gathering
data on the distribution, numbers, and/or composition
of species groups and population monitoring.
of the values/ranges of value
The loss of species
richness in an area can be used as an indicator for
pressures on the environment and can help to define
conservation measures and to avoid further damage.
Values of losses of species (or selected taxonomic
groups) can be fixed with respect to local flora if
Losses in species
number > = 15% = very high incidence
Losses in species number 7.5% < 15% = high incidence
Losses in species number 5 < 7.5% = medium incidence
Losses in species number < 5% = low incidence
Methods of measurement
Number of species
per defined area.
are used for the enumeration and determination of
species richness according to the different taxonomic
groups investigated, as well as particular ecozones
and ecosystems. In general, plant species are recorded
through point, line, plot or plotless vegetation surveys.
The consistency of the assessment method is extremely
important with regard to the monitoring of species
richness. The sampling methods must be adapted to
the particular conditions. Heterogeneous habitats
require more samples than homogenous habitats. Species
richness can also be estimated and there are various
methods existing, mainly based on a species-area correlation.
Limits of the
It is difficult
to obtain up-to date knowledge of the local flora.
It should be stressed that species richness needs
to be used in the context of further indices for biodiversity
and changes of biodiversity. Different ecosystems
naturally support different numbers of species and
species richness is not necessarily an indicator of
high ecological value or stability. It only represents
a basic value for each site which can be used for
the monitoring of species numbers within the same
area or in relation to other variables, e.g. the percentage
threatened species from the total number of species,
etc. The identification, investigation and description
of species can help to understand their roles in the
ecosystems. The identification of species-rich areas
can be helpful to determine priority areas for biodiversity
Land cover, Land
use type, habitat fragmentation, habitat conversion,
indicator species, colonization of habitat by invasive
5. Evaluation of data
needs and availability
to calculate the indicator
With regard to
species inventories, the variety of living species
in even a small area is so great that identifying
all of the species present is generally impractical.
The identification of described species often requires
a high level of expertise. A complete inventory will
therefore not be attainable even at a site-level,
and the surveys will probably have to be limited to
selected taxonomic groups.
Global Plant Checklist:
Genericum (Plantarum): www.nmnh.si.edu/ing/
Organisation for Plant Information: http://iopi.csu.edu.au/iopi
Plant Name Index: www.ipni.org
Type Catalogue: www.nybg.org/bsci/hcol/vasc/
data from national and international sources
Species 2000 is
a "federation" of database organizations
and has the objective of catalogueing all known species
of plants, animals, fungi and microbes on earth as
the baseline dataset for studies of global diversity.
It was established in 1994 by several organizations
and is being developed by a multi-national project
team. Its homepage is accessible at www.species2000.org
the International Programme of Biodiversity Science,
hosted at the International Council for Science (ICSU)
and sponsored by different organizations. It is currently
working on the development of standardized methods
for sampling, assessing and monitoring biodiversity
for various taxa. Information can be obtained from
their homepage www.icsu.org/diversitas.
Center for the Environment (ICE), in cooperation with
the United States Man and the Biosphere Programme
(U.S. MAB) and the Man and the Biosphere (MAB) Programme
of the United Nations Educational, Scientific, and
Cultural Organization (UNESCO), has produced standardized
databases containing species inventories of plants
and animals reported from Biosphere Reserves. The
searchable database is accessible at http://www.arcbc.org/arcbcweb/biodiversitylinks/default.asp?
6. Institutions that
have participated in developing the indicator
7. Additional information
Many efforts have
also been made on a regional level to develop standard
guidelines. A good example is the development of manuals
by the Resources Inventory Committee of the Ministry
of Environment, Lands and Parks of British Columbia.
Forty-one manuals describing particular measurement
methods for different species groups are available
online at www.for.gov.bc.ca/ric/pubs/teBioDiv/index.htm
University of Basilicata
Via dell'Ateneo Lucano
85100 Potenza, Italy