landscape structure and bird species richness: implications for conservation in rural areas between...

Landscape structure and bird species richness: implications

for conservation in rural areas between natural parks

Joan Pinoa,*, Ferran RodaÁa, Josep Ribasb, Xavier Ponsa,c

aCenter for Ecological Research and Forestry Applications (CREAF), Universitat AutoÁnoma de Barcelona, 08193 Bellaterra, SpainbEntenc,a 6, 08100 Mollet del ValleÁs, Spain

cDepartament de Geogra®a, Universitat AutoÁnoma de Barcelona, 08193 Bellaterra, Spain

Received 23 March 1999; received in revised form 30 November 1999; accepted 21 January 2000

Abstract

Regional planning is bound to play an increasing role in nature conservation policies because much biodiversity is located

outside natural parks and other protected areas. Differences in landscape structure between natural parks and surrounding

areas may affect their respective species richness and may provide seasonal habitats that enhance total biodiversity. To test

these ideas, we analyzed patterns of bird species richness, and its associated conservation value in a largely forested rural area

that lies between the natural parks of Sant Llorenc, del Munt and Montseny (Catalonia, NE Spain). Relationships of species

richness with spatial gradients (X and Y Universal Transversal of Mercator (UTM) coordinates) and with altitude and

landscape variables were tested by stepwise multiple regression analysis. Regressions were performed separately for both

breeding and wintering species, and considering both all species and only several dominant ecological groups (forest, forest-

cropland and cropland species). Bird species richness and its associated conservation value were higher in the study area than

in the surrounding borders of natural parks. Cropland and forest-cropland species concentrated outside the natural parks,

whereas forest species were uniformly distributed. Total bird species richness was mainly related to landscape diversity and to

abundance of open habitats like croplands and shrublands. Cropland species were the most dependent on the abundance of

crops and on landscape diversity, whereas forest and forest-cropland species exhibited weak correlations with landscape

variables. Most forest species were year-round residents, whereas forest-cropland and cropland species exhibited seasonal

shifts in the number of species, mainly because of interchanges with other areas. Results indicate that rural areas play a role

complementary to the surrounding natural protected areas in the conservation of bird species richness at different scales.

Implications for the design and optimization of ecological networks in the perimetropolitan area of Barcelona are discussed.

# 2000 Elsevier Science B.V. All rights reserved.

Keywords: Landscape structure; Bird species richness; Rural planning; Conservation biology

1. Introduction

Land-use changes are a major cause in the decline

of biodiversity in recent decades (SouleÂ, 1991; White

et al., 1997). Traditional conservation efforts have

* Corresponding author. Tel.: �34-93-5812915;

fax: �34-93-5811312.

E-mail address: [email protected] (J. Pino)

Landscape and Urban Planning 49 (2000) 35±48

0169-2046/00/$20.00 # 2000 Elsevier Science B.V. All rights reserved.

PII: S 0 1 6 9 - 2 0 4 6 ( 0 0 ) 0 0 0 5 3 - 0

focused on maintaining charismatic (rare, vulnerable,

endangered) species primarily by minimizing expo-

sure to human activities through establishment of

protected areas, but without taking a regional, more

holistic view (Farina, 1998). However, since ecologi-

cal systems are ®rst and foremost networks of inter-

acting populations, the close relationship between the

conservation of the ecological functionality of natural

areas and the preservation of biodiversity is becoming

evident (Solbrig, 1991; Barbault, 1995). Consequently,

traditional conservation thinking has evolved to a new

one that shifts emphasis from species to ecosystems

and even landscapes or regions (Barbault, 1995;

Machado, 1996; Miller et al., 1997; White et al., 1997).

As a result of this trend, the ecological value of

areas placed outside protected sites is increasingly

recognized. Indeed, these areas act not only as lin-

kages between natural areas, but they also take part in

many landscape ecological processes (Felton, 1996).

Conservation policies usually tend to enhance restora-

tion of natural forest and shrubland communities by

promoting land reclamation in these areas, in order to

improve their corridor functions in future ecological

networks (Nowicki, 1996). These policies are related

to current thinking in conservation biology, which

identi®es fragmentation of natural habitats as one of

the major threats for the conservation of ecosystem

functionality worldwide (Hobbs, 1994; MeffeÂ and

Carroll, 1994). However, the design of ecological net-

works rarely takes into consideration areas with abun-

dant seminatural habitats such as crops and pastures,

although these habitats play an important role in the

conservation of ecological processes and endangered

species (Barbault, 1995; Farina, 1995; Paoletti, 1995).

Landscape ecology provides a suitable conceptual

framework for the development of ecological net-

works because it focuses attention on spatial and

temporal dynamics and promotes larger-scale view

than traditional site-based conservation (Forman and

Godron, 1986; Forman, 1995; Rookwood, 1995; Fry,

1996; White et al., 1997). Landscape structure usually

determines and is in turn determined by many, if not

most, ecological processes (Forman and Godron,

1986; Forman, 1995), meaning that spatial analysis

of a landscape might be a sound way to understand the

underlying ecological relationships (Turner and Gard-

ner, 1993; Miller et al., 1997; Farina, 1998). This

analysis has often been performed by not only study-

ing the relative abundance of the different landscape

units but also by de®ning landscape indices that try to

describe landscape structural and functional properties

(Forman and Godron, 1986; Turner, 1989; Colville,

1995; Aronson and Le Floc'h, 1996; Miller et al.,

1997; Farina, 1998).

The aim of this paper is to highlight the role of rural

areas placed outside natural parks in the conservation

of biodiversity and ecosystem processes using simple

landscape analysis. The study analyzed the spatial and

temporal pattern of bird species richness, a major

component of species biodiversity in the Mediterra-

nean region, and its relationship with several relief and

landscape attributes in a largely-forested rural area

sited between natural parks in the perimetropolitan

area of Barcelona. We ®nally discuss the implications

for landscape planning in these areas and also for

optimizing the design of an ecological network in the

perimetropolitan area of Barcelona, where local and

regional administrations are increasingly interested in

developing strategies to enhance biodiversity and

landscape conservation at a regional level.

2. Material and methods

2.1. The study area

The study was carried out in the perimetropolitan

area of Barcelona (Catalonia, NE of Spain), an area

with several mountain ranges dominated by Mediter-

ranean forests and shrublands and ¯oodplains occu-

pied by crops and urban areas (Fig. 1). Conservation

efforts during the last two decades have led to the

establishment of natural parks in the main ranges,

where intense afforestation has been enhanced by land

abandonment and also by conservation policies sub-

sequent to delimitation of protected areas.

A rural area of 480 km2 between Sant Llorenc, del

Munt and Montseny natural parks (Figs. 1 and 2) was

selected for the study. This is a transition area from the

inland plateaus of the Iberian Peninsula to coastal

ranges, with a NW±SE gradient from a continental to a

maritime climate, and also from submediterranean to

Mediterranean conditions. Land cover of the area is

dominated by forests (Table 1), with a gradient from

deciduous oak (Quercus humilis) and Scots pine

(Pinus sylvestris) forests in the NW to holm oak

36 J. Pino et al. / Landscape and Urban Planning 49 (2000) 35±48

(Quercus ilex) and Aleppo pine (Pinus halepensis)

forests in the SE. Non-irrigated herbaceous crops are

abundant in the ¯at areas. Human settlements are

mainly concentrated in the SE area, which is included

into the dispersed urban system around Barcelona.

2.2. Bird species richness

Bird species distribution was studied from 1992 to

1998 by ®eld sampling by one of us (JR). The study

area was divided following the Universal Transversal

of Mercator (UTM) 1 km�1 km squares. Each of

these UTM squares were sampled once or twice a

year for both breeding and wintering species. Sam-

plings were conducted from March to July to record

breeding species (i.e. those species that displayed

reproductive activity in their reproductive habitat

and during their reproductive period), and from

November to February to record wintering species.

In each sampling, a transect of about 1±1.5 h of

Fig. 1. Geographic location of the study area, between the natural parks of Sant Llorenc, del Munt and Montseny in the central coastal area of

Catalonia (NE Spain). The main natural areas and cities of the perimetropolitan area of Barcelona are represented in grey and black areas,

respectively. Small border corresponds to the study area.

J. Pino et al. / Landscape and Urban Planning 49 (2000) 35±48 37

duration was made each year by walking within each

UTM square. Along these transects, bird species were

recorded by both visual and hearing contacts, and

main habitat preferences were assigned to each of

them.

Species were assigned to one of these habitat

categories according to their predominant ecology:

aquatic habitats, crops, forests, shrublands, rocks and

cliffs, urban habitats, and several combinations of

them (forests±crops, rocks±crops, urban±crops). This

assignment was performed basically from ®eld data,

and also from bibliographic sources (Baucells et al.,

1999). Data concerning species as a whole and for

each habitat category were summarized in the number

of both breeding and wintering species per UTM

square, and converted to raster format using MiraMon,

an in-house developed geographic information system

(GIS) (Marcer and Pons, 1998).

2.3. Conservation value

Species were also classi®ed according to their

conservation status using two indices derived from

Fig. 2. Land-use map of the study area in 1987 based on a reclassi®cation of Landsat categories. Minimal and maximal UTM-31N coordinates

(in m) are shown. The study area is that included within the small border. Black convolute lines correspond to the limits of Sant Llorenc, del

Munt (left) and Montseny (right) natural parks.

Table 1

Landsat landscape units in the study area (1987)

Landsat landscape unitsa Relative ground cover

Coniferous (pine) forests 0.445

Shrublands 0.214

Herbaceous non-irrigated crops 0.162

Sclerophyllous oak forests 0.071

Urban dispersed areas 0.023

Deciduous oak forests 0.022

Herbaceous irrigated crops 0.021

Denuded areas 0.016

Towns and villages 0.014

Non-irrigated orchards 0.011

Industrial areas 0.018

Irrigated orchards 0.001

Vineyards 0.001

a VinÄas and Baulies (1995).


the EU Birds Directive (70/409/CEE) and the IUCN

criteria for Spanish vertebrates (Blanco and Gonzalez,

1992). The Directive-based index was computed by

assigning a value of 1 to the species included in the

Birds Directive, and 0 to the remaining species. For

the IUCN-based index, species were scored as 0 (not

threatened), 1 (insuf®cient data), 2 (non-determined),

3 (rare), 4 (vulnerable), and 5 (threatened). For each

index, and separately for nesting and wintering spe-

cies, the conservation values of all species present

within each UTM 1 km�1 km square were summed

and rasterized, yielding maps of the distribution of the

conservation importance for the bird fauna in the study

area.

2.4. Landscape information

The landscape structure of the study area was

analyzed from a land-use raster generated by the

Cartographic Institute of Catalonia (ICC) using multi-

spectral TM images obtained by the satellite Landsat 5

during 1987 (VinÄas and Baulies, 1995). After succes-

sive processes of simpli®cation and classi®cation, the

de®nitive raster had a spatial resolution of

30 m�30 m, and included the thematic categories

or landscape units shown in Table 1.

This land use raster was used to calculate several

landscape indices for each 1 km�1 km UTM square:

1. Habitat diversity H�ÿP pi log�pi�, correspond-

ing to Shannon and Weaver's diversity index

calculated for each UTM square, where pi

corresponds to the proportion of the area covered

by each landscape category, and log is the

logarithm to base 2.

2. Habitat dominance D� Hmax �P

pi log�pi�� =Hmax, which measures the value of dominance of

one landscape category over the others. Hmax

corresponds to the maximum Shannon diversity

index, calculated as the log of the number of

landscape categories.

3. Landscape microscale heterogeneity, measured by

means of two patchiness indices: the number of

different landscape categories (NDC) and the

number of landscape categories different from

that of the central cell (CVN). Both indices were

calculated in a grid of 3�3 cells around each cell

in the land use raster, and subsequently their mean

value for each UTM 1 km�1 km was obtained.

The GIS Idrisi was used for this purpose.

2.5. Altitude data

Data on the relief of the study area were obtained

from a Digital Elevation Model (DEM) generated by

the ICC from topographic 1:50,000 maps. The DEM

has a spatial resolution of 45 m and it was used to

calculate the minimal, mean and maximal altitudes

within each UTM 1 km�1 km square.

2.6. Spatial variability of bird species richness and

relationship with relief and landscape variables

Factors affecting the spatial distribution of bird

species richness were analyzed considering different

variability sources: (1) a set of physical and landscape

parameters, (2) regional gradients, and (3) the remain-

ing autocorrelation at a more local level. Stepwise

multiple regression analysis was used to assess the

signi®cance of landscape and relief variables and that

of spatial gradients in explaining the spatial pattern of

both breeding and wintering bird species richness.

Stepwise multiple regression, already used in similar

studies (Rafe et al., 1985), adds independent variables

accounting for their contribution to total variance, thus

giving an ordination of relative importance (from

more to less) of these variables in the regression.

Altitude data, landscape indices, and the cover

proportion of the different landscape units were con-

sidered as physical and landscape variables. Land-

scape units were grouped into basic categories

(forests, shrublands, crops, urban areas and other) to

reduce the number of independent variables and thus

increase the robustness of the analysis. A third-order

polynomial constructed with X and Y UTM coordi-

nates was added to the model to account for the spatial

variability due to regional and local gradients, thus

performing a trend surface analysis in the regression

model (Burrough and McDonell, 1998). X and Y

coordinates were previously rescaled by subtraction

of their means in order to avoid collinearity problems

derived from the inclusion of the different th-power

terms of the polynomial (Rawlings et al., 1998). The

inclusion of surface analysis in the regression model

permitted the reduction of autocorrelation to accep-

table levels. Indeed, maximum Moran coef®cients


(Cliff and Ord, 1981) calculated for each regression

model ranged from 0.15 to 0.28.

Stepwise regression analyses were performed sepa-

rately for nesting and wintering species, ®rst pooling

together all habitats, and thereafter for species

grouped into forest, cropland and forest-cropland

categories, which were the predominant species

groups in the study area. Correlation analyses between

all landscape, altitude and position variables were

previously performed in order to select the de®nitive

independent variables. As a result, landscape domi-

nance and heterogeneity indices, and maximal and

minimal altitudes were rejected because they were

highly correlated (r2>0.8) with landscape diversity

and mean altitude, respectively. Forest cover was also

discarded because of its high negative correlation with

cropland and shrubland cover (multiple r2�0.98).

Final variables considered in the analyses are sum-

marized in Table 2.

3. Results

3.1. Distribution and components of birds species

richness

A total of 114 nesting and 108 wintering bird

species were recorded in the study area. Spatial rich-

ness of both breeding and wintering bird species was

not uniformly distributed across the study area (Fig. 3),

but concentrated mainly in the SE and in the N. These

areas correspond respectively to the ValleÁs and the

MoianeÁs plains, with an heterogeneous landscape

made up by a matrix of non-irrigated herbaceous crops

and abundant forest and human settlement patches.

The rest of the study area, with a more homogeneous

landscape broadly dominated by forests and shrub-

lands, exhibited much lower values of bird species

richness. The conservation value of bird fauna exhib-

ited a similar pattern (Fig. 4). Indeed, high values of

both UE Birds Directive and IUCN indices associated

with either nesting or wintering species concentrated

outside the natural parks. Correlation between both

indices was moderate (r2�0.39) for nesting species

and high (r2�0.80) for wintering species.

The majority of bird species were classi®ed into

three ecological groups: forest species (24% of all

nesting species and 20% of wintering species), crop-

land species (16% of nesting and 28% of wintering

species) and forest-cropland species (25% of nesting

and 14% of wintering species). The spatial distribution

of species richness for these main groups was rather

different (Fig. 5). In a manner similar to total species

richness, cropland species concentrated outside the

natural parks, and mainly to the N and the SE of the

study area where open habitats (mainly dry-land

herbaceous crops and fallows) are dominant. Forest-

cropland species were also more concentrated in

agricultural areas, mainly in the N where the land-

scape is made up by a crop±forest mosaic. In contrast,

forest species richness exhibited a more uniform

Table 2

Variables used in the different stepwise multiple regression

analysesa

Variables

Dependent variables

Nesting species

Total number of species

Number of forest species

Number of cropland species

Number of forest-cropland species

Wintering species

Total number of species

Number of forest species

Number of cropland species

Number of forest-cropland species

Independent variables

Landscape

Diversity index

Relative shrubland cover

Relative cropland cover

Relative cover of urban areas

Relief

Mean altitude

Position

UTM X coordinate

UTM Y coordinate

X2 coordinate

Y2 coordinate

XY coordinate

X3 coordinate

Y3 coordinate

XY2 coordinate

X2Y coordinate

a Regression analyses were performed using all the independent

variables for each dependent variable.


Fig. 3. Spatial pattern of breeding and wintering bird species richness in the study area. Legend gives the number of bird species for each

UTM 1 km�1 km square. White lines correspond to the limits of Sant Llorenc, del Munt (left) and Montseny (right) natural parks. Plotted area

coincides with the small border of Fig. 2.


distribution, with only lower values in the rural areas

of the SE corner where forests are residual. For each

group, the distribution pattern of bird species richness

was similar between seasons, although changes in the

number of species were observed.

3.2. Spatial variability of bird species richness and

relationships with landscape and relief

Stepwise multiple regression analyses for nesting

species are summarized in Table 3. There were 10

Fig. 4. Spatial pattern of the conservation importance of both nesting and wintering bird species richness, according to EU Birds Directive and

IUCN criteria. Legend gives for each UTM 1 km�1 km square the number of bird species included in the EU Directive and the mean

conservation value according to IUCN criteria (0: not threatened, 1: insuf®cient data, 2: non-determined, 3: rare, 4: vulnerable, and 5:

threatened). Black lines correspond to the limits of Sant Llorenc, del Munt (left) and Montseny (right) natural parks. Plotted area coincides with

the small border of Fig. 2.


variables signi®cantly correlated with the spatial

variations of total nesting species richness (accumu-

lated r2�0.389, F10,448�28.493, p<0.0001). Cropland

cover was the most signi®cant variable (multiple r2

change�0.144), displaying a positive correlation,

and was followed by shrubland cover (0.098), the

X coordinate (0.039), and landscape diversity

(0.044). Cropland species exhibited a closer relation-

ship with the independent variables (r2�0.712,

F9447�122.88, p<0.0001). The most signi®cant

variable was cropland cover (multiple r2 change�0.625) which exhibited a positive relationship with

cropland nesting species richness and represented

88% of the total correlation. Forest and forest-

cropland species showed weaker relationships with

the selected variables than cropland species

(r2�0.462, F12,444�31.800, p<0.0001 for forest spe-

cies and r2�0.394, F13,443�22.184, p<0.0001 for

Fig. 5. Spatial pattern of breeding and wintering bird species richness for the main ecological groups of birds in the study area. Legend gives

the number of bird species for each UTM 1 km�1 km square. Black lines correspond to the limits of Sant Llorenc, del Munt (left) and

Montseny (right) natural parks. Plotted area coincides with the small border of Fig. 2.


forest-cropland species). Forest species were

mainly correlated with the cover of croplands

(r2 change�0.297) and urban areas (0.087), both

with negative correlations. Forest-cropland species

were positively correlated with shrubland cover

(r2 change�0.194) and also with the X coordinate

(0.140).

Stepwise multiple regression analyses performed

for wintering species are summarized in Table 4. Total

wintering species richness was more closely corre-

lated with the selected variables than nesting species

richness (accumulated r2�0.488, F10,448�42.633,

p<0.0001). Cropland cover was the most correlated

variable (r2 change�0.367), followed by landscape

diversity (0.044). In a manner similar to cropland

nesting species, cropland wintering species richness

exhibited a close relationship with the independent

variables (r2�0.646, F12,444�67.396, p<0.0001). The

most correlated variable was cropland cover (multiple

r2 change�0.563) followed by landscape diversity

(0.041), both with positive correlations. In contrast,

forest and forest-cropland species showed weak cor-

relations with landscape and relief variables

(r2�0.225, F9447�14.399, p<0.0001 for forest spe-

cies, and r2�0.293, F10,446�18.479, p<0.0001 for

forest-cropland species). Forest species richness was

mainly and negatively correlated with cropland cover

(r2 change �0.131). In contrast, forest-cropland spe-

cies richness was positively correlated with the crop-

land (r2 change�0.130) and shrubland (0.108) cover.

Species richness of the different groups exhibited

signi®cant and negative correlations with single, quad-

ratic and cubic terms of UTM X, Y coordinates,

indicating a non-negligible effect of spatial gradients.

However, since position variables usually occupy the

third or fourth position in the stepwise regression

analyses and multiple correlations between the

third-order XY polynomial and the dependent vari-

ables represented about a half of total correlation

(ranging from 0.14 for forest-cropland nesting species

to 0.33 for cropland nesting species), it can be con-

sidered that the effect of position variables was less

important than that of landscape variables in explain-

ing the variability of bird species richness.

Table 3

Stepwise multiple regression analyses for nesting bird species richnessa

Variables Regression coefficient

(�standard error)

Accumulated

multiple r2

Significance

(p)

1. Total nesting species

Relative cropland cover 11.78�1.46 0.144 <0.0001

Relative shrubland cover 6.91�1.62 0.243 <0.0001

X coordinate (km) ÿ0.287�0.055 0.281 <0.0001

Landscape diversity 4.11�0.86 0.325 <0.0001

2. Cropland species



X3 coordinate (km3) ÿ0.0001�0.0003 0.675 <0.0001

XY coordinate (km2) ÿ0.013�0.003 0.688 0.0047

3. Forest species

Relative cropland cover ÿ6.44�0.68 0.297 <0.0001

Relative cover of urban areas ÿ10.39�1.60 0.384 <0.0001

Mean altitude (m) 0.002�0.001 0.414 <0.0001

X2 coordinate (km2) ÿ0.012�0.003 0.428 0.0010

4. Forest-cropland species



X coordinate (km) ÿ0.261�0.057 0.323 <0.0001


a Only the four most correlated variables are shown for each regression.


3.3. Ecological groups and their seasonal shifts

The main ecological groups considered in the study

(forest, cropland, and forest-cropland species) exhib-

ited contrasting species shifts from nesting to winter-

ing seasons (Fig. 6). Forest species richness remained

relatively constant over the year, with 29 nesting species

and 24 wintering species. The majority of species (21)

remained for the winter, and the small shifts primarily

took place between habitats within the study area. Crop-

land speciesexhibiteda clear increase in speciesnumber

(from 19 nesting to 33 wintering) mainly due to arrivals

from outside the study area (14 species), and also from

other habitats within the study area (eight species). In

contrast, the number of forest-cropland species de-

creased from 30 nesting to 16 wintering, mainly due

to species migrating outside the study area (17 species).

4. Discussion

In our study area, whose landscape is mostly domi-

nated by forests, nesting and wintering species rich-

Table 4

Stepwise multiple regression analyses for wintering bird species richnessa

Variables Regression coefficient

(�standard error)

Accumulated

multiple r2

Significance

(p)

1. Total wintering species



XY2 coordinate (km3) ÿ0.005�0.001 0.446 <0.0001

X2 coordinate (km2) ÿ0.021�0.006 0.454 0.0078

2. Cropland species



X3 coordinate (km3) ÿ0.0005�0.0003 0.614 0.0003

Relative cover of urban areas 5.26�1.89 0.620 0.0065

3. Forest species

Relative cropland cover ÿ3.57�0.61 0.131 <0.0001

X2 coordinate (km2) ÿ0.007�0.003 0.157 0.0002

XY coordinate (km2) ÿ0.012�0.003 0.179 0.0005

Relative cover of urban areas ÿ2.29�1.23 0.189 0.0230

4. Forest-cropland species



XY2 coordinate (km3) ÿ0.012�0.0004 0.267 0.0002

Y coordinate (km) 0.062�0.023 0.275 0.0284

a Only the four most correlated variables are shown for each regression.

Fig. 6. Seasonal bird species shifts in the main ecological groups

considered. Figures are number of bird species. Arrows indicate

changes from nesting to wintering seasons.


ness are signi®cantly related to landscape diversity

and landscape attributes that affect diversity, like the

abundance of several open habitats such as croplands

and shrublands within the forest matrix. These results

agree with other previous works that demonstrate the

important role of landscape structure and diversity in

determining the number of available habitats which, in

turn, in¯uences the number of species (Pearson, 1993;

Farina, 1995; Miller et al., 1997). Indeed, landscape

heterogeneity helps to increase the predictive power of

species±area models for bird species (Rafe et al.,

1985; Boecklen, 1986). In our case, relationships

between landscape and species richness are signi®cant

and relatively close even though they can be affected

by the low spatial resolution used in the study

(1 km�1 km), and methodological artifacts related

to the fact that landscapes are usually measured from

a human perspective rather than from a wildlife per-

spective (Fry, 1996).

Since total bird species richness summarizes a

composite response of the habitat needs of individual

species (Mùller, 1987; Hansen and Urban, 1992), the

performance of separate regression analysis for

the main ecological groups of birds allows to increase

the predictive power of the model. Regression ana-

lyses performed for the main ecological groups of

birds (forest, cropland and forest-cropland species)

showed contrasting responses to landscape patterns.

Cropland species were highly dependent on the abun-

dance of crops (mainly herbaceous non-irrigated

crops) and on landscape diversity, as can be expected

in a landscape with a matrix made up by forests and

shrublands. In contrast, forest species, which exploit

the forest matrix and thus exhibit a relatively uniform

distribution, showed only a weak relationship with

landscape variables, especially during the wintering

period.

Our study highlights the importance of the rural

area placed between Sant Llorenc, del Munt and Mon-

tseny natural parks for bird preservation in the peri-

metropolitan area of Barcelona. The conservation

value of this area is not related only to the absolute

number of species but also to their conservation status

and their inclusion in the list of species that need

special conservation measures. Indeed, several threa-

tened birds of prey such as Bubo bubo (Eagle-Owl),

Hieraetus fasciatus (Bonelli's Eagle), Falco peregri-

nus (Peregrine Falcon), Circaetus gallicus (Short-toed

Eagle) and Circus cyaneus (Northern Harrier), and a

number of species living in open habitats are found in

these rural areas but are rare or even absent in the

adjacent protected areas.

In addition, because of the combination of natural,

seminatural, and urban habitats, rural areas are becom-

ing hot spots of landscape diversity that allow a high

concentration of species with contrasting habitat

needs. This is particularly valuable in perimetropoli-

tan environments where, in a manner similar to other

areas of the Mediterranean region (Farina, 1991;

Naveh, 1993; Makhzoumi, 1996), intense processes

of land abandonment and afforestation affecting the

traditional landscape are causing a gradual decrease in

landscape diversity and complexity. These processes

of land use change have been particularly intense in

mountain areas, which often enjoy protected status. As

a result, these areas have undergone a progressive

enrichment in forest species and also a decrease in

total species richness due to the gradual disappearance

of species living in open areas. Therefore, rural areas

adjacent to mountains are becoming more and more

important for the conservation of cropland and forest-

cropland birds, as indicated by the grouped distribu-

tion of these species in the study area (Fig. 6).

Seasonal species shifts also have implications for

bird conservation at a regional scale (Farina, 1995).

While the assemblage of forest bird species is the most

stable over the year, cropland and forest-cropland

species groups are more dynamic and undergo notice-

able species shifts from nesting to wintering seasons.

These shifts are determined by not only habitat

changes within the same area but also by interchanges

with other adjacent or separate regions. Indeed, spe-

cies such as Serinus serinus and Emberiza cirlus

seasonally migrate at a regional scale from forests

in adjacent mountain areas in summer to open habitats

in ¯at areas in winter. Similarly, many migrating birds

such as C. cyaneus use croplands as wintering areas or

as stepping stones in their long way northwards or

southwards, thus indicating that agricultural land-

scapes also play an important ecological role at

broader spatial scales.

Several implications of these results might be con-

sidered for the design, management and conservation

of bird species richness in the perimetropolitan area of

Barcelona. Traditional planning, management and

conservation strategies that have promoted land aban-


donment and afforestation in protected areas should be

complemented by others that consider the role of

semi-natural and agricultural landscapes in providing

for landscape, ecological and species biodiversity and

for conserving natural resources (Yokohari et al.,

1994; Makhzoumi, 1996). This might allow to pre-

serve the existing landscape diversity, thus helping to

maintain bird species richness at the landscape scale.

On the other hand, ¯at agricultural areas and the

adjacent natural parks play complementary roles in

maintaining biodiversity components at a regional

scale. While rural areas are occupied by open-habitat

species and are also used by a heterogeneous pool of

species as wintering areas, natural protected areas

house many endangered species and, also, large popu-

lations of forest bird species that increase the coloni-

zation probability of small and isolated woodlots in

the adjacent ¯at areas. A sound planning strategy

would be the design of ecological networks that would

include natural protected areas as core areas and rural

adjacent areas as buffers, corridors or nature devel-

opment areas (Nowicki, 1996). To achieve this, and

since natural protected areas are often designed and

managed so that a maximum number of habitats or

charismatic species are represented (Pickett and

Thompson, 1978; Boecklen, 1986), it is important

to develop regional policies that evaluate rural land-

scapes for their ecological services as well as for their

economic value (Naveh and Leiberman, 1990).

Acknowledgements

This study has been funded by the Servei d'AccioÂ

Territorial of the DiputacioÂ de Barcelona. The authors

also wish to thank J. Retana and R. Salvador for their

advice in performing statistical analyses.

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Joan Pino has a Ph.D. in biology (1995) from the University of

Barcelona (Spain) and an M.S. degree in geographic information

technology (1998) from the Autonomous University of Barcelona.

He is also lecturer of botany and plant ecology at the University of

Barcelona and a researcher at the Center for Ecological Research

and Forestry Applications (CREAF). His major research topics are

dynamics and management of plant populations, and the applica-

tion of landscape ecology to nature conservation in perimetropo-

litan areas.

Ferran RodaÁ has a Ph.D. in biology (1983) from the Autonomous

University of Barcelona and is Full Professor of ecology at the

same University. He has been the director of CREAF since 1998.

His main fields of research interest are the functional ecology of

terrestrial ecosystems (namely the hydrology, biogeochemistry,

primary production and fire ecology of Mediterranean forests and

shrublands), and the applications of landscape ecology to nature

conservation.

Josep Ribas has a biology degree from the Autonomous University

of Barcelona and he is doing his Ph.D. at the University of

Barcelona. His major research topic is the study of the bird fauna in

rural areas around Barcelona. He has been monitoring bird

populations of these areas for more than 6 years and he has

contributed with these data to the Bird Atlas of Catalonia (NE of

Spain).

Xavier Pons has a Ph.D. in remote sensing and GIS (1992) and an

M.S. degree in geography (1995) from the Autonomous University

of Barcelona. He is Associate Professor at the Department of

Geography of the Autonomous University of Barcelona and a

coordinator of research activities in GIS and remote sensing at

CREAF. His main work is on radiometric and geometric

corrections of satellite imagery, cartography of ecological para-

meters from airborne sensors, spectral responses of Mediterranean

vegetation, and GIS development. He has recently worked on

descriptive climatology models, on modelling forest fire hazards

and on the analysis of landscape changes from a long series of

satellite images.


landscape structure and bird species richness: implications for conservation in rural areas between...

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