Conservation and Sustainable Use of the Biosphere - WBGU

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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

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