Conservation and Sustainable Use of the Biosphere - WBGU

Human use of species: the higher plants D 1.3
39
Box D 1.3-3
The importance of orchids as indicators of
environmental change
In Section D 1.1 the orchids were highlighted as an
extremely species-rich family where one might have the
impression that loss of species diversity has little consequence
for the functioning of ecosystems. In this section, the
orchid flora of Thuringia is used as an example to illustrate
how this species-rich plant group is actually a very sensitive
indicator of environmental change.
Thuringia has 51 species of orchids, the most diverse
orchid flora in Germany; five of the species previously identified
are now extinct, however (Arbeitskreis Heimische
Orchideen Thüringen e.V., 1997). The distribution of each
individual species has been documented since 1577, and in a
more intense and extremely detailed fashion since the middle
of the 19th century, so that today maps are available
which can be used to understand trends in the distribution
of orchids over time. Ordnance survey quadrants serve as a
basis for the distribution maps.
The distribution and diversity of orchids found at some
time or another in Thuringia was overwhelming; there was
hardly a quadrant without orchids. The top figure was 43
species and was recorded in the area of Jena. Comparison
with the species found since 1990 shows that in almost 16
per cent of the quadrants orchids can no longer be found.
And the total number of species has also declined sharply.
This decline has occurred in both common and rarer
species. Fig. D 1.3-2 shows the distribution of all species
before and after 1990 in all quadrants of Thuringia. Species
that were found in fewer than 100 quadrants have either
become extinct or have been pushed back into just 10 per
cent of the sites (lower section of the curve). Species that
were present in 100–200 quadrants are now found in only
half of the sites. Even species with much more extensive distribution
(>200 quadrants) have lost on average 40 per cent
of their sites. Fig. D 1.3-3 uses the example of the greenwinged
orchid (Orchis morio) to demonstrate the dramatic
decline of this striking species group (Arbeitskreis Heimische
Orchideen Thüringen e.V., 1997). This is all the more
remarkable since orchids are protected by conservation
measures and so enjoy greater protection than other
species.
Number of survey quadrants after 1990
400
300
200
100
0
The causes for the loss of orchid diversity include
changed land use, drainage of wetlands, intensification of
grass-land management and forestry, advancing construction
around large towns and cities and increasing eutrophication
as a result of airborne nitrogen loading.
The disappearance of the orchids, therefore, is a measure
of humankind’s intervention into the natural balance. One
can assume that there was not a decline in the total number
of species in each area, but that sensitive, non-competitive
species gave way to a group of more robust species able to
withstand human disruptions. In that way a group of plants
that, other than through beauty, have no direct ‘function’ for
humankind has become a highly sensitive environmental
indicator.
1:1
0 100 200 300 400 500
Number of survey quadrants before 1990
Figure D 1.3-2
Occurrence of all orchid species in each of the quadrants of
the 1:25 000 map of Thuringia, presented for the period
before 1990 and after 1990.
Source: Arbeitskreis Heimische Orchideen Thüringen e. V.
[Working group on domestic orchids in Thuringia], 1997
Figure D 1.3-3
Reports of the green-winged
orchid (Orchis morio) in
Thuringia. Note that in
earlier floral studies often
no location was reported
since the species was
widespread and also called
‘Gemeines Knabenkraut’ [ie
common green-winged
orchid]. Currently there are
just a handful of sites with a
few individuals and the
species is acutely threatened
with extinction.
Source: Arbeitskreis
Heimische Orchideen
Thüringen e. V., 1997
N
51°
50°
10° 11° 12°
before 1900
1900–1949
1950–1969
1970–1989
since 1990
E