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Jensen, RA, Madsen, J, O'Connell, Mark ORCID: 0000-0003-
3402-8880, Wisz, M, Tommervik, H and Mehlums, F (2008)
Prediction of the distribution of Arctic‐nesting pink‐footed
geese under a warmer climate scenario. Global Change
Biology, 14 (1). pp. 1-10. doi:10.1111/j.1365-
2486.2007.01461.x
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Prediction of the distribution of Arctic-nesting pink-footed geese under a warmer climate scenario
RIKKE A. JENSEN *, JESPER MADSEN *, MARK O’CONNELL w, MARY S. WISZ*, HANS TØMMERVIK z
and FRIDTJOF MEHLUM § 2
*Department of Arctic Environment, National Environmental Research Institute, University of
Aarhus, Frederiksborgvej 399, PO Box 358, DK-4000 Roskilde, Denmark, wDepartment of Biology and
Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, zDivision of Arctic Ecology,
Norwegian Institute for Nature Research, The Polar Environmental Centre, N-9296 Troms, Norway,
§Natural History Museum, University of Oslo, PO Box 1172, Blindern, N-0318 Oslo, Norway
Abstract
Global climate change is expected to shift species ranges polewards, with a risk of range contractions
and population declines of especially high-Arctic species. We built species distribution models for
Svalbard-nesting pink-footed geese to relate their occurrence to environmental and climatic
variables, and used the models to predict their distribution under a warmer climate scenario. The
most parsimonious model included mean May temperature, the number of frost-free months and
the proportion of moist and wet moss-dominated vegetation in the area. The two climate variables
are indicators for whether geese can physiologically fulfil the breeding cycle or not and the moss
vegetation is an indicator of suitable feeding conditions. Projections of the distribution to warmer
climate scenarios propose a large north- and eastward expansion of the potential breeding range on
Svalbard even at modest temperature increases (1 and 2
o
C increase in summer temperature,
respectively). Contrary to recent suggestions regarding future distributions of Arctic wildlife, we
predict that warming may lead to a further growth in population size of, at least some, Arctic
breeding geese.
Keywords: Anser brachyrhynchus, Arctic, biodiversity, climate change, climate envelope, species
distribution models, Svalbard
Received 4 October 2006; revised version received 21 February 2007 and accepted 9 July 2007
Correspondence: Rikke A. Jensen, tel. 145 46301940, fax 145 45301914, e-mail: raj@dmu.dk
1 Present address: Hartpury College, University of West England, GL19 3BE Gloucestershire, UK.
2 Present address: Research Council of Norway, PO Box 2700, St Hanshaugen, N-0131 Oslo, Norway.
Introduction
Global climate change is predicted to have strong effects on the distribution and abundance of Arctic
animal and plant populations. Ranges of individual species may move polewards, expand or decline
in extent, and in mountain areas, move towards higher elevations (Boyd & Madsen, 1997; Parmesan
et al., 1999; Thomas & Lennon, 1999; Hickling et al., 2006). Particularly in the high-Arctic regions and
islands where the range of species is limited by the Arctic ocean, it is predicted that effects will be
mostly negative because the habitats of tundra living species will be squeezed by higher vegetation
(Zöckler & Lysenko, 2000; ACIA, 2005).
Migratory, Arctic-nesting birds have a narrow time window for breeding, moulting and
preparation for return migration between the time of thaw and before the Arctic winter sets in. The
northern limits of breeding range are largely determined by the minimum period physiologically
required to complete the breeding cycle (e.g. Newton, 1977), provided that suitable habitat is
present. In Svalbard, nesting goose species (i.e. the brent goose, Branta bernicla, barnacle goose,
Branta leucopsis and pink-footed goose, Anser brachyrhynchus), arrive late May to early June and
migrate south around mid September, a period of <4 months which coincides with the time of frost-
free and snow-free conditions (Prop & De Vries, 1993; Madsen et al., 1998). Their timing and success
of breeding are highly variable, depending on snow and ice conditions on arrival, summer and
premigratory weather conditions (Owen & Black, 1989; Prop & De Vries, 1993; Madsen et al., 2007).
The size of all three Svalbard goose populations has increased in recent decades. In barnacle and
pink-footed geese, the proportions of successful breeding pairs and brood sizes have declined with
increasing population sizes (Trinder et al., 2005; M. Trinder & J. Madsen, unpublished data),
suggesting that density-dependent factors are now affecting their productivity. In barnacle geese,
the available area for brood rearing appears to be a limiting factor (Drent et al., 1998). In pink-footed
geese, it is more likely that availability of suitable nest sites is limiting (Madsen et al., 2007), possibly
in combination with availability of spring staging feeding habitat in which the geese gain body
reserves of critical importance for the subsequent breeding success.
The growing goose populations give rise to management concerns in their wintering range
due to conflicts with agriculture (e.g. Van Eerden et al., 1996) and, increasingly, in the Arctic due to
potential grazing effects on the fragile tundra ecosystems (e.g. Loonen & Solheim, 1998; Abraham et
al., 2005; Van der Wal et al., 2007). Therefore, to inform management about the expected future
directions of these conflicts, it is important to assess the impacts of warming of the Arctic. We
examine whether warming will have a pronounced effect on the potential breeding range of the
geese in the Svalbard archipelago compared with their present distribution, focussing on the pink-
footed goose which has the widest distribution of the three species. A landscape based nesting
habitat suitability model (resolution 15 m) for a central part of its breeding range showed that pink-
footed geese prefer to nest on south facing slopes in the lowland, in close connection to suitable
feeding sites which are wet moss-dominated areas (Wisz et al., in press). Upscaling the model to
cover entire Svalbard (resolution 1 km), we hypothesize that at the regional scale the present
distribution of pink-footed geese is determined by (1) the length of the season with frost-free
conditions, which sets the limit for whether geese can physiologically fulfil the breeding cycle or not,
(2) the temperature in May which indicates availability of areas providing geese with early feeding
and nesting opportunities, (3) suitable feeding habitats and (4) elevation.
Based on the present potential distribution, we predict future distributions of pink-footed
geese under a warmer climate scenario.
Materials and methods
Study population
The Svalbard-breeding population of the pink-footed goose winters in Denmark, the Netherlands
and Belgium, with autumn and spring stopover sites in Norway. The population has increased from
approximately 15 000 individuals in the 1960s to more than 50 000 in 2003 (Fox et al., 2005). The
pink-footed goose breeds in loosely aggregated colonies, mainly along the west coast and in the
interior lowlands of the western parts of Svalbard. It breeds on small islands, as well as on the open
tundra, being capable of defending its nest against avian predators, as well as Arctic foxes, Alopex
lagopus (Mehlum, 1998).
Spatial data layers
For modelling the potential distribution of nesting pinkfooted geese, we used known presence of
nests, environmental and climatic predictors. Our sample units consist of grid cells of 926.6 m by
926.6 m. For simplicity we refer to these as grid cells of 1 km
2
. As large parts of Svalbard is covered
with glacier (approximately 55 000 km
2
) only cells with no glacier were considered in the analysis.
This area consists of 10 498 cells. Areas disturbed by human activity are included in the analysis, but
their extent is negligible compared with the total area.
Nest records. Data were derived from: (1) The database of the Norwegian Polar Institute with
records from 1962 to 1996. Only data with geographical coordinates and records of nests were used,
whereas records of broods were not used. The accuracy of the coordinates is generally within 1 km
2
.
(2) Recent nest surveys in different parts of Nordenskiöldland: (a) Sassendalen in the interior of
Isfjorden, 2003–2004 (Wisz et al., in press); (b) Nordenskiöldkysten, 2004 (J. Prop, unpublished data),
(c) Reindalen, 2004 (J. U. Jepsen, unpublished data); (d) Vårsolbukta, 2004 (C. Hübner, unpublished
data) and (e) Adventdalen, 2004 (D. Kuijper, unpublished data) (Fig. 1). In the recent studies, nest
positions were recorded with a GPS with an accuracy of c. 50 m.
From these sources 692 nest records and accurate coordinates could be derived. After
relating these to a 1 km
2
grid and assigning one presence record for each cell containing one or more
nests, 111 records of nest presences were available for analysis.
Vegetation. A vegetation cover map with four major classes relevant for geese was developed for
entire Svalbard, based on Landsat Thematic Mapper with a 28 m spatial resolution (H. Tømmervik, in
preparation, see Wisz et al., in press). The relevant classes are (1) dry heath dominated by Dryas
octopetala, Cassiope tetragona and Carex spp., (2) bare ground with sparsely vegetated patches
dominated by Saxifraga oppositifolia, (3) moist moss dominated fen with mixed coverage of
Bistorta vivipara, Salix polaris, Equisetum spp., Eriophorum spp. and Carex spp. and (4) wet moss
carpet, dominated by mosses and Dupontia spp. For the purpose of the present analysis, we only
used the area of moist- and wet moss-dominated habitat, expressed as proportion for each 1 km
2
grid cell, which is the preferred feeding habitat during the prenesting and nesting period and a
significant predictor in the landscape nest site model (Wisz et al., in press). Nest presences were
observed at proportions of moist/wet moss in a range from 0.0 to 0.85.
Elevation. A digital elevation model DEM with a 20 m spatial resolution was made available for the
project from the Norwegian Polar Institute (Fig. 1). From this map mean elevation was calculated in
the coarser resolution of 1 km
2
grid cells. Elevation was a significant predictor in the landscape nest
site model (Wisz et al., in press). Nest presences were observed at elevations ranging from 0 to
632m.
Surface temperature. We used MODIS satellite imager-derived land surface temperature and
emissivity (Friedl et al., 2002; Petitcollin & Vermote, 2002) at a spatial resolution of 1 km
2
grid cells.
We chose a temporal resolution averaging values across the middle 8 days of each month. Monthly
temperature values for the years 2001–2004 were obtained, and subsequently reprojected using
bespoke MODIS data manipulation tools (USGS EROS Data Center, 2002). Pixel values were averaged
across all available years (two to four) to create a single mean monthly value (to nearest 0.5
o
C) for
each 1 km
2
grid cell over the entire area of Svalbard (Fig. 2). Thus, a frost-free month is defined as a
month where the average temperature across the middle 8 days is above 0
o
C. The cells with three
frost-free months are concentrated along the west coast, in the valleys that debouch into the
western fiords and in the western lowlands of Edgeøya. Nordenskiöldland has some of the largest
continuous areas with three or four frost-free months. Nest presences were observed in cells with a
Fig. 2 Current surface map of frost-free months on Svalbard.
