ecological process indicators used for nature protection scenarious in agricultural landscapes of sw
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This article is also available online at:www.elsevier.com/locate/ecolind
Ecological Indicators 7 (2007) 396–411
Ecological process indicators used for nature protection
scenarios in agricultural landscapes of SW Norway
Annette Bar a,b, Jorg Loffler a,*
a University of Bonn, Department of Geography, Germanyb University of Oldenburg, Institute of Biology and Environmental Sciences, Germany
Received 1 November 2005; received in revised form 5 April 2006; accepted 6 April 2006
Abstract
Conflicts between changing landscapes and static nature protection concepts were addressed as an example of the
agricultural landscape of SW Norway. We aimed to deduce indicators for spatio-temporal landscape changes to draw scenarios
for future protection perspectives of a RAMSAR and nature reserve. To estimate the variability of bird diversity, changes in
vegetation patterns were analysed to predict bird occurrence. We obtained a differentiated analysis of present landscape
dynamics by measuring landscape structure, vegetation, hydrology and nutrient concentration. Multivariate statistics were used
to extract the main driving forces for changes in vegetation patterns out of a complex landscape ecological data set.
Subsequently, we compared the measured data with those of past landscape stages to determine landscape changes and their
mechanisms at different spatio-temporal scales. Ecological process indicators (EPI) were derived, and three different indicator
constellations were used for scenario descriptions. These scenarios were chosen as to the current assumptions of typical
contrasting nature protection strategies. Concluding, we used EPIs to evaluate nature protection aims and to assess scenarios of
changing landscapes. This approach will be transferable to other examples of nature protection conflicts in the agricultural
landscape in general.
# 2006 Elsevier Ltd. All rights reserved.
Keywords: Biodiversity; Landscape dynamics; Landscape management; Landscape metrics; RAMSAR reserve; Sustainable development;
Vegetation mapping; Wetland ecosystems
1. Introduction
Cultural landscapes show spatio-temporal changes
of landscape structures according to intensive human
impact and natural succession (Lundberg, 2000;
* Corresponding author. Tel.: +49 228 73 7239.
E-mail address: [email protected] (J. Loffler).
1470-160X/$ – see front matter # 2006 Elsevier Ltd. All rights reserved
doi:10.1016/j.ecolind.2006.04.001
Waldhardt et al., 2004). Thus, current discussions
about changing landscapes and process-oriented
protection strategies (Pickett et al., 1992; Lundberg,
1996; Skanes, 1997) have to consider the question of
appropriate protection. As an example of the
agricultural landscape of SW Norway, we chose a
study area at Lake Grudevatn (Jæren). High diversity
in plant and bird life led to the designation of the site as
.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 397
nature reserve in 1974 and as a RAMSAR reserve
(convention on wetlands signed in Ramsar, Iran 1971)
in 1985 (Wetlands International, 2004). High plant and
bird diversity as a reason for protection was not further
specified in the protection aims, so it remained unclear
what kind of species composition was desired:
a species composition of traditional agricultural
landscapes, in coincident with wetland protection
(RAMSAR), a species composition of minimal
anthropogenic disturbed areas, or a mosaic of both
which favors high total species numbers but of more
common species. Consequently, nor monitoring of
plant and bird species occurrence neither landscape
management measures have been carried out to
observe landscape changes or to maintain a desired
status of species composition within the protected
area. Thus, the landscape character has strongly
changed since 1974 caused mainly by shifts in
distribution and composition of vegetation units.
Due to the lack of specified protection aims and
continuing monitoring data the challenge was to use
the approach of ‘‘space-for-time substitution’’ (Pickett
et al., 1992). This approach should be combined with
available external data about past landscape stages in
order to determine ongoing and past changes. Our
study was framed by a general increasing interest in
deducing indicators to monitor environmental change
(Tiner, 2004). Our approach was focused on devel-
oping ecological indicators that represented different
vegetation transforming processes at different spatial
scales and time perspectives, hereafter referred to as
ecological process indicators (EPI). In detail, these
indicators should be extracted by mapping recent
vegetation patterns and measuring corresponding
hydrological and nutritional conditions. The structural
status quo of the landscape should then be compared
with past stages of spatial vegetation succession over
the past decades. As it is known that bird occurrence,
abundance and habitat selection is strongly influenced
by vegetation structures (Cody, 1987; Jones, 2001;
Tonu et al., 2005), the information about changes in
vegetation patterns should be used to estimate the
variability of bird diversity.
Using the derived EPIs to adjust different variable
constellations we aimed to suggest scenarios to
illustrate landscape changes and possible future
developments with respect to their relevance for bird
life at Lake Grudevatn. We intended to focus on major
principles of medium- and long-term landscape
changes; precise predictions of short-term configura-
tions of species and species numbers were not
intended. Our sub-goals were:
(a) t
o test a combination of multi-scale environmentalvariables and methods, including a short inves-
tigation period combined with different historic
data sources in order to determine the complex of
medium-term and long-term landscape transform-
ing processes,
(b) t
o use vegetation changes as predictor for birddiversity, and
(c) t
o derive EPIs for scenarios of landscapedevelopment in a RAMSAR and nature reserve
by addressing conflicts between changing land-
scapes and static nature protection concepts.
2. Material and methods
Field work was carried out at Lake Grudevatn, Klepp
community (Jæren, SW Norway). The wetland is
protected as bird and nature reserve, covering 110 and
47 ha of land, respectively, and is surrounded by
intensively used arable land and pasture resulting in
considerable nutrient supply caused by drainage ditches
(Molværsmyr et al., 1989; Molværsmyr, 1990). The
water table shows high oscillations and flooding occurs
regularly. During the 20th century substantial anthro-
pogenic changes were caused by drainage measures in
order to extend the amount of agricultural land. Water
table lowering and an increased nutrient supply caused
rapid vegetation succession and accelerated sedimenta-
tion at the lake shores (Olafsrud, 1993).
Fig. 1 describes our methodological approach at
different spatio-temporal scales. The present status
quo of the bird and nature reserve was investigated
between May and August 2002. Vegetation was
mapped at 115 single square plots (5 m � 5 m)
aggregated to 18 transects along different topographic
and moisture gradients around the lake. The distance
between the plots was determined for each transect
according to the change of plant species compositions.
Plant species abundance was recorded using the
Domin-scale (Kent and Coker, 1992). On the micro-
scale, vegetation types were defined after Fremstad
(1997) whose scheme was often used as a national
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411398
Fig. 1. Methodological approach used in the study at different spatio-temporal scales.
reference in Norway. For each vegetation plot one soil
sample was collected. Soil profile features, soil
moisture, and soil structure were recorded after Boden
(1996). The pH was measured at 10, 20 and 30 cm
depth in H2O and CaCl2 as a volumetric sample-liquid
proportion of 1:2.5 in the field. Additionally, type and
degree of land use (e.g. kind of grazing animals) were
mapped and classified into five utilisation intensities
per grazing type. Classification was done by estima-
tion and internal ranking of trampling and browsing.
Hydrological investigations were carried out by
measuring the water table variations at 17 sites
weekly using tide gauges. At these points conductivity
was determined within the same intervals. Due to the
spatial array of measuring points in transects at
different vegetation units around the lake it was
possible to analyse nutrient fluxes subjected to
structural site conditions and hydrological regimes.
Changes in vegetation patterns were studied over a
period of 65 years. Historic data sources were used
such as aerial photos, vegetation type maps and long-
term measurements of hydrology and nutrient con-
centrations in the catchment area (Table 1). On the
meso-scale, land use units were classified which were
based on aerial photos from 1937, 1954 and 1989 and
GIS-based maps were derived for each year. These
maps were based on land use units and provide
information about landscape structures focusing on
both the reserve and its surroundings. Land use units
consisted of classified single patches characterized by
the same land use type. Based on these, landscape
metrics enabled a quantification of landscape struc-
tures (McGarigal and Marks, 1994). By comparing the
same area using three time sequences of aerial photos
structural landscape changes were studied. ‘‘Mean
patch size’’ (MPS) and ‘‘mean nearest neighbour’’
(MNN) were determined using the ArcView extension
‘‘patch 2.0’’. Landscape changes were expressed by
e.g. increasing/decreasing MPS for each year and land
use category. The MPS reflected changes especially of
the agricultural landscapes quite well due to distinct
land use borders (McGarigal and Marks, 1994) and
indicated landscape uniformity. Wetland connected-
ness which is important for migratory birds was
analysed by MNN distance calculations between
patches of the same land use type.
Finally, our newly produced vegetation type map
from 2002 was compared with the one from 1992
(Olafsrud, 1993) allowing to study qualitative changes
over a medium-term period. This comparison pro-
vided the option to differentiate vegetation changes
within the protection area in addition to the aerial
photo analyses with a focus on land use changes. For
argumentation concerning vegetation changes we
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 399
Table 1
Measured variables and external environmental data sources
Environmental
variables
Methods External sources References
Land use GIS-based analysis Aerial photos from 1937,
1954, and 1989
Fjellanger Widerøe (1937, 1954, 1989),
and personal communication with land
owners and administration authorities
Vegetation Vegetation mapping Vegetation type map 1992 Olafsrud (1993)
Soils Soil profile description,
pH and soil moisture
measurements
Soil type map 1962 Semb (1962), Boden (1996)
Hydrology Water table measurements
(wells and gauges)
Water table measurement
(Figgjo-River 1984–2002)
Molværsmyr et al. (1989), Molværsmyr
(1990), Fylkesmannen i Rogaland (1996),
Vikse (1998)
Nutrients Water conductivity
measurements (wells and
gauges)
Nitrogen and phosphor
concentration (1984–2002)
Fylkesmannen i Rogaland (1996), Vikse
(1998), Solberg (personal communication)
Breeding birds Reports, personal communication Løvbrekke (1992a,b, 1995, unpublished data)
referred to Nedkvitne et al. (1995), Pott (1995),
Fremstad (1997), Pott and Remy (2000) and Succow
and Joosten (2001).
External data of nutrient amounts and water table
fluctuations from the Figgjo-River were used to set the
current measurements into a longer time perspective
(K. Solberg, unpublished data).
For data on breeding bird communities in the study
area, we could not rely on own fieldwork results.
Species composition, species abundance and trends in
population development between 1979 and 2002
could coarsely be characterised evaluating Løvbrekke
(1992a,b, 1995) and using comments of local
ornithologists (Løvbrekke, unpublished data and
personal communication, 2002). Following the
‘‘guild’’ concept (Simberloff and Dayan, 1991;
Wilson, 1999), a set of ‘‘typical’’ species was assigned
to the following vegetation/land use units each:
eutroph lake and lakeshore, reed, fen and mesophile
grassland, arable land, and willow shrub and similar
early succession stages.
Since there is no accepted guild concept for
northern European bird communities, we used the
species assignment by Flade (1994) developed for
northern German vegetation units, but adapted it to
local conditions by adding/removing species to guilds
based on our own field experience. Hence, our
modification lacks the strictly statistical approach
but does reflect local circumstances much better.
Prediction of occurrence and population trends was
based on the current bird fauna situation and trends
between 1992 and 2002. Species treatment was based
on Clements (2000) inclusive all supplements to-date.
In order to extract major vegetation patterns in
relation to environmental variables, we applied
multivariate ordination techniques (Ter Braak and
Prentice, 1988; Ter Braak and Smilauer, 1998). Plant
species abundance was used in combination with
nominal data for structural environmental variables
and different quantified environmental variables. The
main environmental variables were extracted out of a
set of 24 environmental variables based on their
significance and colinearity. A Canonical Correspon-
dence Analysis (CCA; Ter Braak, 1986) was applied
on 118 species. The position of the species represented
their relation to the involved ecological gradients (Ter
Braak, 1994; Jongman et al., 1995).
Based on ordination vegetation complexes were
delimited by differences in soil moisture, nutrient
supply and land use. Characteristic plant species could
be assigned. A schematic section along a gradient
from the lake to arable land illustrates the recent
ecological conditions based on the extracted environ-
mental variables for the nature reserve. We used data
about past landscape stages concerning landscape
structure, vegetation, hydrology and nutrient concen-
tration and combined them with our results of recent
landscape patterns and functioning. Thus, we were
able to determine landscape changes and their
mechanisms on different spatio-temporal scales to
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411400
determine EPIs. These were interpreted as the main
driving forces for vegetation changes, and thus for
changes in species composition of breeding birds.
Vegetation succession was used to visualize the
tendency of vegetation changes by EPIs.
For future protection perspectives three scenarios
were created distinguishing different configurations of
the EPIs. Three contrasting scenarios were chosen in
agreement with the most widespread current assump-
tions of nature protection strategies: (1) emphasis on
protection of natural succession, (2) emphasis on the
preservation of a static cultural landscape for the
protection of certain species including extensive
conservation measures, and (3) a mixture of both
approaches. Based on our temporal analyses land-
scape changes will occur at different temporal scales
and anthropogenic changes can be gradual e.g.
nutrient accumulation and abrupt e.g. land use
transformation. Causes and consequences of manage-
ment measures are different for several processes,
such as for plant species composition and vegetation
type changes up to 10 years contrasting to sedimenta-
tion processes lasting more than 10 years. Thus, the
time horizon for described scenario perspectives
depends on the processes. We illustrated different
effects of process indication:
� S
cenario 1 describes future development based onthe status quo. Applying this scenario, all current
transforming processes will continue the trends
observed during the last decades concerning both
stronger natural vegetation succession and the
strengthened impact of intensified and extended
agricultural use. In reality, this scenario often
results from conflicts in land use (nature protection
versus agricultural use) and a lack of landscape
management initiative. However, it can be desirable
under the perspective of mosaic-cycle protection
aims (Remmert et al., 1991). In cultural landscapes
it is not suitable to preserve current plant and bird
diversity in many cases.
� S
cenario 2 was geared to certain landscapemanagement interventions as well as to landscape
conservation targets. This scenario is a realistic
option in the implementation of management
measures concerning preservation of a certain
stage, and maintaining the current plant and bird
species diversity. Some of the measures supporting
this scenario were already partly introduced during
the campaign for an improvement of water quality
in Jæren (Vikse, 1998).
� T
he landscape management strategy suggested inscenario 3 postulates substantial changes in land
cultivation. This scenario describes the most fictive
perspective for the area. There is no consensus for a
transition of intensive land use into an economically
less productive type under the current socio-
agricultural situation. In fact, this nature protection
strategy would be the most substantial one
concerning preservation of current plant and bird
diversity and the improvement of the characteristic
traditional landscape.
3. Results
On the meso-scale, aerial photo analyses showed
continuing processes of landscape changes between
past stages of the study area from 1937 to 1954 and to
1989 (Fig. 2). Especially arable land expanded
drastically where areas could be used for agricultural
purposes. The area of arable land in total was enlarged
from 25.5 ha in 1937 to 77.5 ha in 1954 and to 161 ha
in 1989. The transformation of grassland into arable
land took place in two different steps. While arable
land emerged from grassland within the same small
parcels of land at the first time sequence (from 1937 to
1954), the managed units did not persist from 1954 to
1989 any longer. During the second period, arable land
extended into areas without former agricultural use
and was suited to efficient mechanical soil cultivation
in size and shape. The increase in MPS of arable land
reflects kinds of changes due to more efficient
agricultural management on bigger and equalised
land units. Increase of fen-MPS and decrease in fen-
MNN at the same time is a result of the loss of smaller
wetland areas at the expense of arable land. MPS of
grassland and forest decreased in total area, drastically
between 1954 and 1989. Apart from the tendency
towards reduction in general, the number of patches
increased continuously while MNN between forest
patches decreased. This illustrates that widespread
forest were under fragmentation into smaller units.
Currently, all described processes of land transforma-
tion are still ongoing (own observations in 2002, and
personal communication with authorities and farmers)
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 401
Fig. 2. Spatio-temporal distribution of land use units and configuration of landscape structures in 1937, 1954 and 1989 analysed on the basis of
aerial photos. Analysis of landscape structure changes was based on landscape metrics mean patch size (MPS) and mean nearest neighbor
(MNN) (McGarigal and Marks, 1994) for the years 1937, 1954 and 1989. Results were differentiated for each land use unit (patch level) and year
(modified after Bar et al., 2004).
even causing more pronounced transition zone
between intensively used agricultural land and
remaining protected wetlands.
On the micro-scale, natural processes caused
vegetation succession e.g. in Kvernebekken bay first
and foremost combined with sedimentation (Fig. 3).
This was forced by eutrophic site conditions. The
vegetation type maps provide more detailed informa-
tion about these changes for the period between 1992
and 2002. Especially in bays, changes ran fast and reed
vegetation expanded remarkably. Consequently, spe-
cies-poor reedbeds dominated by Phragmites australis
increased in area and currently dominate the
sedimentation zones. Growth of bouncing lawns
strengthened the fast sedimentation in the bays. Along
streaming exposed sites riparian vegetation was built
by dense Schoenoplectus lacustris stands. Between
1992 and 2002 the fen vegetation belt changed in plant
species composition due to higher nutrient concentra-
tions. These areas were invaded by Phalaris arundi-
nacea to a large extent. Vegetation formerly either
characterized by sedge species such as Carex rostrata
or mosaics of Potentilla palustris, Galium palustre,
Lysimachia thyrsiflora, and Myosotis palustris turned
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411402
Fig. 3. Spatial distribution of vegetation types presented for the Kvernebekken-bay. The maps are based on vegetation mapping in 1992 by
Olafsrud (1993) and in 2002 by Bar et al. (2004). Vegetation types were recorded after Fremstad (1997) (modified after Bar et al., 2004).
into species-poor patches. The fast and widespread
expansion of Salix-shrubs and tall forbs along the
transition zones between the organic and mineral soils
was remarkable.
Measurements of the hydrologic variability and the
nutrient dynamics gave more detailed information
about the current spatio-temporal dynamics within the
nature reserve (Fig. 4). The groundwater table in the
present fen areas proved to be permanently high.
Oscillation was mainly caused by flooding. Yet, fen
edge and mineral soils were characterised by
fluctuations of the groundwater table. In comparison
with long-term water table measurements of the
Figgjo-River over the past 20 years amplitudes
increased since the 1980s. This indicates more
frequent and intensive flooding than in former times.
One reason is land transformation into arable land in
the entire catchment which caused a reduced water
storage capacity and led directly to a run-off and thus
to more intensive flooding.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 403
Fig. 4. Results of water table and conductivity variations based on weekly measurements between 27th May and 21st August 2002 are presented
in the diagrams. Conductivity concentration is illustrated in columns while the water level is given as lines. The diagrams represent ground water
measurements (B) including two measuring points at different distances to the waterside. The data gap in the middle of the period was caused by
extremely high flooding events when measuring was not possible anymore. Site variables as moisture and pH values at different depth as well as
soil type and grazing were recorded once within the investigation period in order to characterize site conditions (modified after Bar et al., 2004).
The nutrient regime was closely connected with
hydrologic conditions (Fig. 4). Current measurements
showed that large quantities of nutrients were
transported from canals into the area and the
groundwater was permanently nutrient enriched.
Agricultural land is well drained so that precipitation
water could run-off to lower parts, e.g. the fen areas.
Measured conductivity in ground water tables strongly
depended on the current hydrologic situation and on
the distance between river bank and arable land. A low
ground water table caused higher nutrient concentra-
tion close to the riverbank. This situation reversed
when the water table rises close to or above surface.
Sites close to the riverbank were flooded which had a
thinning effect on nutrient concentrations. As a result
measured conductivity was higher at the upper sites
with greater distance to the river bank. The
conductivity of soils in bays hardly varied as to lake
shore distance, but was generally found to be very
high. No streaming potentiated the fact that nutrient-
enriched sediments could depose over the preceding
years causing eutrophic site conditions. Long-term
measurements showed that nitrogen concentration
hardly decreased since the 1980s. Phosphorus con-
centrations were high until 2000, since then a distinct
decrease was observed (Molværsmyr, 1990; K.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411404
Solberg, personal communication, 2002). Nitrophile
riparian vegetation spread along the riverbank. Dense
stands of tall herbs reduced the hydraulic stream flow
capacity, resulting in backwaters and thus intensify
flooding.
The hydrologic-nutritional situation in combina-
tion with grazing pressure showed direct impact on the
establishment of shrubs and forbs as well. These
benefited from a good nutrient supply caused by a
lower groundwater table which allows organic matter
to be mineralised. In addition, trampling of grazing
animals as mainly cattle caused severe damages
shaping an undulating surface and opened ground
patches. At such patches, germination is facilitated,
thus spreading and growth of shrubs and forbs was
enforced. Intensity of agricultural land use present as
Fig. 5. Results of a canonical correspondence analysis (CCA) for 118 plan
(shown as arrows and quadrats) were extracted. Based on these variables, c
intensive grazing within the protection area and high
nutrient supply from fertilisation mainly from outside
the reserve were figured out to be the main driving
forces for the changes.
Six main vegetation complexes could be classified
based on variable constellations and ordination
(Fig. 5). The ordination diagram shows how recent
plant compositions were determined by the environ-
mental variables. Plant species classified as reed/lake
shore vegetation (2) were more influenced by nitrogen
than the fen plants species (3). The lake shore complex
represents sites of reed vegetation that receives
nutrients from the river and canals. Salix species
(marked in black triangles) mainly occurred along the
transition zone (4) between the fen area (3) and pasture
land and illustrated the invasion of shrubs in fen areas.
t species and 24 environmental variables. Major ecological variables
urrent vegetation patterns were classified into vegetation complexes.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 405
The two grassland complexes (5a and 5b) strongly
differed in their dependence on nutrient supply and
grazing pressure. Arable land (6) presented the sixth
complex. For each vegetation complexes representa-
tive plant species are shown. The impact of all
investigated environmental variables were aggregated
in a schematic landscape ecological concept (Fig. 6).
Analysis of bird mapping between 1979 and 2002
led to the following conclusions (Table 2). Bird
species of fens and extensive grassland (‘‘meadow-
birds’’ cf. Beintema et al., 1995) experienced a large
decline. Out of 14 species assigned to this guild, 3
(Black Grouse Tetrao tetrix, Corncrake Crex crex,
Short-eared Owl Asio flammeus) were extinct already
in 1979, a further five species (Dunlin Calidris alpine,
Black-tailed Godwit Limosa limosa, Ruff Philoma-
chus pugnax, Yellow Wagtail Motacilla f. flava and
Whinchat Saxicola rubetra) disappeared until 2002.
Numbers of Common Snipe Gallinago gallinago and
Eurasian Curlew Numenius arquatus stayed stable
(eight and four pairs in 2002, respectively), on
Redshank Tringa totanus and Northern Lapwing
Fig. 6. The impacts of all investigated environmental variables were aggreg
environmental variables are presented below. Moisture and nutrient gradi
Vanellus vanellus, no information is available. Data
on birds breeding at the lakeshore (Great Crested
Podiceps cristatus and Little Grebe Tachybabtus
ruficollis, different dabbling ducks Anatinae, Coot
Fulica atra) is deficient, but probably no severe
declines took place, except in Garganey Anas
querquedula. Gull counts in 1992 and 2002 showed
a strong decrease in Black-headed Gull Larus
ridibundus numbers (125–150 pairs to 3 pairs), and
a marked increase in Common Gull Larus canus
numbers (2–5 pairs to 10–24 pairs). Species diversity
and numbers of breeding pairs increased in bird
communities characteristic for early succession stages
(willow shrub). Chiffchaff Phylloscopus collybita was
first recorded breeding in 1992, and numbers of this
species increased strongly until 2002. However,
numbers of further species indicating succession
processes stayed stable (e.g. Reed Bunting Emberiza
schoeniclus) or declined (Greater Whitethroat Sylvia
communis).
Based on ecological measurements in comparison
with former stages of the study area EPIs were derived
ated in a schematic landscape ecological concept. Major gradients of
ents were related to near-surface conditions.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411406
Table 2
Main vegetation units, corresponding bird guilds and trends in species population development 1979–2002
Vegetation unit/land use type Species Trend 1979–2002
Eutroph lake and lakeshore
Little Grebe Tachybaptus ruficollis ?
Mute Swan Cygnus olor 0
Eurasian Wigeon Anas penelope ?
Garganey Anas querquedula ?
Northern Shoveler Anas clypeata ?
Common Gull Larus canus +
Black-headed Gull Larus ridibundus �
Reeds
Water Rail Rallus aquaticus ?
Sedge Warbler Acrocephalus schoenobaenus ?
European Reed Warbler Acrocephalus scirpaceus ?
Fen and mesophile grassland
Black Grouse Tetrao tetrix ��Corncrake Crex crex ��Northern Lapwing Vanellus vanellus ?
Dunlin Calidris alpina ��Common Snipe Gallinago gallinago 0
Eurasian Curlew Numenius arquata 0
Black-tailed Godwit Limosa limosa ��Common Redshank Tringa totanus ?
Ruff Philomachus pugnax ��Short-eared Owl Asio flammeus ��Eurasian Skylark Alauda arvensis ?
Yellow Wagtail Motacilla flava flava �Northern Wheatear Oenanthe oenanthe 0
Whinchat Saxicola rubetra ��
Arable land
Northern Lapwing Vanellus vanellus ?
Yellowhammer Emberiza citrinella ++
Willow shrub and earlier successions
Greater Whitethroat Sylvia communis ��Willow Warbler Phylloscopus trochilus 0
Chiffchaff Phylloscopus collybita ?
Reed Bunting Emberiza schoeniclus 0
��: strong decline; �: decline; 0: numbers stable; +: increase; ++: strong increase; ?: no population numbers available.
(Fig. 7). These were defined as the main driving
forces. Ecological process indication for the lake shore
areas was sedimentation in bays which led to nutrient
accumulation as to nutrient enriched sediments. The
decrease of the water storage capacity due to land use
transformation into arable land and their drainage led
to more frequent and intensive flooding. In addition,
nitrophile dense riparian vegetation spread and forced
flooding intensity by backwater. For vegetation
succession this meant that nitrophile reed vegetation
characterized by species-poor high and dense stands
expanded. Accordingly, population numbers of reed
inhabiting bird species such as Sedge Warbler
Acrocephalus schoenobaenus and Eurasian Reed
Warbler Acrocephalus scirpaceus might have
increased. Depending on the availability of mudflats
and reedbeds in shallow water, Water Rail Rallus
aquaticus might have become a regular breeder.
Nutrient accumulation was also evident in the fen
complex caused by changing flooding regimes and
nutrient supply from surrounding agriculture land and
as consequence of former water table lowering. Thus,
mineralization processes started, additionally forced
by trampling of grazing animals. The gaps in
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 407
Fig. 7. Based on the landscape scheme (Fig. 6) the status quo was defined by the most important environmental variables (moisture, nutrients,
and land use) and vegetation units with characteristic plant and bird species compositions were assigned. EPIs (grey boxes) were derived out of
the complex interactions of all environmental variables within each vegetation complex.
vegetation offered the opportunity for nitrophile
shrubs and forbs to germinate. Consequently, fen
vegetation was invaded in wetter parts by reed
vegetation, in drier parts shrubs and forbs germinated
and typical low and sparse fen plant species got lost.
This created a mosaic habitat consisting of swamps,
dense reed vegetation and pioneer shrub areas. Reed
bunting, Chiffchaff, Willow warbler Phylloscopus
trochilus and possibly some Sylvia warblers might
have benefited from the situation and increased in
territories.
The process regime in the transition complex is
rather similar to what was found in the fen areas. Due
to drier soil conditions and trampling mineralization
was advanced. Shrubs and forbs were already
established. Typical pasture determined plant species
could spread towards the transition zone because of
drier soil conditions and higher grazing pressure.
An EPI for the wet and drier grassland was the
invasion of shrubs from the transition zone where
vegetation could not be heavily grazed due to
comparatively wet site conditions. In addition further
drainage measures lowered the water table and led to
shrub growth and soil mineralization. Nutrient supply
was high because of direct fertilisation and eluvia-
tions from arable land. Thus, high productive grass-
land species spread at drier parts and changed natural
grassland communities. Where it was economical
reasonable grassland was transformed into arable
land.
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411408
Fig. 8. Scenarios based on different EPI constellations for future developments. Main aspects are shown and changes are exemplarily illustrated
for each scenario.
Fig. 8 describes consequences of different con-
stellations of EPI-based scenarios for future develop-
ments.
Scenario 1 implicates that nutrient supply and
cultivation pressure could still be high. This is evident
from a current ongoing expansion of arable land and
may stop directly at the nature reserve border.
Accordingly, drainage measurements might be accom-
plished which would also have an impact on the nature
reserve itself. Nutrient supply also continues to be high.
The nature reserve could continue to loose its
attractiveness for breeding wetland and meadow bird
species. Numbers of Common Snipe and Eurasian
Curlew would probably drop down, a re-colonisation by
more sensitive species such as Corncrake or Short-eared
Owl is excluded in this scenario. In general, birds
specialised on different habitat features would be
replaced by more ubiquitous species.
In scenario 2, cultivation pressure might stop.
Consequently, no further transformation into arable
land and attached drainage would take place. A few
constructed wetlands might be built in some afferent
canals causing a reduction of nutrient outfluxes. In fact,
the nutrient supply would be reduced to a certain
degree, and especially phosphorus would be reduced by
up to 61% (Fylkesmannen i Rogaland, 1996). However,
the reduction might not stop further sedimentation and
the expansion of shrubs and forbs. If conservation of
meadow birds was a goal in this scenario, management
measures would have to be implemented. Removal of
shrubs, restoration of the natural water table and
appropriate extensive land use are minimum require-
ments to maintain the current situation (cf. Beintema
et al., 1995). Extinct species would probably not return
to the area in this scenario. The implementation of this
kind of landscape management would only have a
medium-term effect, because nutrient supply would
still be high and would cause fast re-growth. On the
other hand, these management interventions might help
to maintain the current diversity in bird species of open
landscapes.
Scenario 3 presents a substantial change in land
cultivation which aims at a broad reduction of
nutrients achieved by constructed wetlands in all
streams. In addition, strong fertilisation restrictions
might be implemented within the reserve. Compulsory
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411 409
edge strips of non-fertilised land would function as
buffer zones and prevent direct nutrient flux into surface
water. These regulations of land use would have to be
compensated by a substantial financial support. Within
the nature reserve the use of wet grasslands as meadows
rather than as pastures would have to be supported. The
conversion into meadows or extensive pastures might
prevent the disturbance of wetland breeding birds. Also,
fens would be protected against additional eutrophica-
tion, mineralization, and invading shrubs, since
trampling would not destroy the upper organic layers.
Nevertheless, succession might not be avoided com-
pletely, as changes would still be natural as a
consequence of lake ageing. Bird life diversity would
be expected to be high. Numbers of species of the fen/
grassland group (especially not very sensitive ones, like
Northern Lapwing and Eurasian Curlew) might
stabilise or even increase. A return of several extinct
breeders such as Black-tailed Godwit to the area seems
possible with an improvement in habitat quality by
more extensive agricultural use, but strongly depends
on overall population numbers and trends in the region.
Species preferring agriculturally used areas (such as
Yellowhammer) would probably not show a further
increase in numbers and might even decline.
4. Discussion
The attractiveness of the nature reserve Lake
Grudevatn evolved from its complex natural conditions,
diverse landscape structures and moderate agricultural
impact resulting in a diversity of vegetation units as well
as faunistic habitats (Wetlands International, 2004).
The interactions between anthropogenic and natural
processes are complex and vary greatly in direction, rate
and scale (Jones, 1991). Formerly, bird diversity was
high including species of open landscapes (i.e. L.
limosa), as well as those depending on dense vegetation
structures such as reeds, shrubs and forests (Løvbrekke,
1995). But during the last decades many areas in the
agricultural landscape were strongly influenced by
anthropogenic variables and landscape transformation
happened rapidly (Moss, 2000). Thus, bird species
composition was changed although bird species
richness remained high at Lake Grudevatn (Løvbrekke,
1992a, b, 1995). But this rather resulted from the mosaic
of agricultural land and small remaining protected
wetlands. Our results confirmed that this patch-context
effect (Dunning et al., 1992; Thies and Tscharntke,
1999) had a strong impact on species composition in the
SW Norwegian landscape. Within this context, the
protection of bird diversity following a static protection
philosophy failed under a perspective of protecting bird
species compositions of the characteristic wetlands
within an extensively used traditional agricultural
landscape. Agricultural activities were intensified
outside the protected area and nutrient supply caused
substantial changes in the vegetation (Bar et al., 2004).
Thus, even the effort of landscape management
measures is limited and could neither prevent sedi-
mentation processes nor reverse vegetation succession
completely. Nevertheless, this fact should not be
interpreted as an argument against protection efforts
in general. High bird species diversity will be desirable,
if protection aims focus on extensive anthropogenic
impact in coincident with wetland protection main-
tained by drainage prohibitions and extensive pastures
(Wetlands International, 2004). To apply sustainable
management measures successfully, it will be important
to develop an integrative management plan based on
changing natural conditions, changing human impact,
and realistic future options (Opdam et al., 2002;
Lundberg, 2004; Loffler and Steinhardt, 2004).
Combining EPI-based estimations of changes in
vegetation patterns at different spatial scales and time
perspectives with the variability of bird species
diversity proved to be applicable. Moreover, we
succeeded to test a combination of multi-scale
environmental variables and methods, including a
short investigation period combined with different
historic data sources. By using vegetation changes the
complex of medium- and long-term landscape
transforming processes could be determined and
helped illustrating bird species changes better than
solely studies based on fragmentary bird data.
However, general negative trends in bird species
occurrence have to be investigated within a wider
context. The different constellations of EPIs for
scenarios partially consider this fact and address
conflicts between changing landscapes and static
nature protection concepts. Since other studies showed
that the ecological mechanisms behind the more
common ‘‘non-scientific’’ indicator approaches
needed further validation within their geographical
context (Cousins and Lindborg, 2004), our EPI-based
A. Bar, J. Loffler / Ecological Indicators 7 (2007) 396–411410
approach might be used as a tool to solve similar
nature protection problems.
Prognostic indicator-based studies are directed to
landscape planning and management and thus of
particular interest for local administrators (Venturelli
and Galli, 2006). Since northern European wetlands
and extensive pastures are one of the most threatened
habitats in the rural landscape and thus in the focus of
protection plans, it is necessary to assess effects of
management and landscape changes (Cousins and
Lindborg, 2004). The crucial point is that nature
protection areas in agricultural landscapes of northern
Europe are seldom found and the few small ones are
very isolated and still influenced by their agricultural
surroundings (Bar et al., 2004). This was also found
for central European cultural landscapes (Jedicke,
1994). Thus, the interest to maintain these remaining
areas increased in order to protect a large number of
ecotypes and species diversity (Arler, 2000). Further-
more, it is important to define protection aims and
introduce management measures if necessary. Our
scenarios are no predictions but they show in which
direction development might take place and how
protection aims have to be adjusted within a realistic
frame. The approach is usable for protection areas
where protection aims are neither specified nor fit into
the recent protection strategy, and where long-term
monitoring data do not exist. Such scenarios might be
used to describe potentials and limits of calls for
actions for different protection strategies.
Acknowledgements
We would like to thank Johannes Kamp (Old-
enburg, Germany) for support on ornithological data
interpretation, Professor Anders Lundberg (Bergen,
Norway) for hospitality, cooperation, botanical and
nature protection expertise, and two reviewers for
helpful suggestions to improve the paper.
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