ARTICLE IN PRESS
Global Environmental Change 16 (2006) 19–28
www.elsevier.com/locate/gloenvcha
Impacts of different climate stabilisation scenarios on
plant species in Europe
Michel Bakkenes, Bas Eickhout, Rob Alkemade
Netherlands Environmental Assessment Agency (RIVM-MNP), P.O. Box 303, 3720 AH Bilthoven, The Netherlands
Received 17 January 2005; received in revised form 2 November 2005; accepted 3 November 2005
Abstract
With the use of goals from the Convention on Biological Diversity we evaluated two climate stabilisation profiles on their merits for
conservation of biodiversity, comparing them with a baseline profile. Focusing on plant ecosystems at the pan-European level, we
concluded that although a maximum global-mean temperature increase of 2 1C is likely to be met in a 550 ppmv CO2-equivalent
stabilisation profile, large areas of ecosystems in Europe will be affected. Most of the impacts manifest themselves in northern countries,
with a high net increase of plant species, and in Mediterranean countries, with a decrease in the number of plant species and stable area.
Other impacts are less robust, given the regional variation in climate results for different climate models.
r 2005 Elsevier Ltd. All rights reserved.
Keywords: Biodiversity; Climate change; Stabilisation profiles; Integrated assessment; Scenario analysis
1. Introduction
Global and European climate have changed notably in
recent decades (EEA, 2004). Temperatures are rising,
precipitation in many parts of Europe is changing and
weather extremes show an increasing frequency in some
regions (IPCC, 2001a). According to the UN Intergovernmental Panel on Climate Change (IPCC), ‘‘there is new and
stronger evidence that most of the warming observed over
the last 50 years is attributable to human activities, in
particular to the emission of greenhouse gases’’ (IPCC,
2001a). Consequences of climate change will also include
losses of biodiversity. Parmesan and Yohe (2003) concluded that climate change already affects species distribution in many parts of the world, including Europe. In
northwestern Europe (EEA, 2004) thermophilic (heatdemanding) plant species have become significantly more
frequent compared with 30 years ago.
The impact of future climate change on plant species
composition will increase in the coming decades. IPCC
Corresponding author. Tel.: +31 0 30 2742955; fax: +31 0 30 274 4485.
E-mail addresses: [email protected] (M. Bakkenes),
[email protected] (B. Eickhout).
0959-3780/$ - see front matter r 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.gloenvcha.2005.11.001
(2001b) concluded that future climate change is estimated
to exacerbate the loss of species, especially those species
with strict climate and habitat requirements, and limited
migration capabilities. Moreover, Thomas et al. (2004)
concluded that climate change may have a major impact on
the number and variety of living organisms and predict that
3–21% of all endemic plant species of Europe may be
committed to extinction by 2050.
These results show possible consequences of climate
change if no climate mitigation policies are implemented.
The ultimate objective of the United Nations Framework
Convention on Climate Change (UNFCCC), as stated in
Article 2, is to ‘‘achieve stabilization of greenhouse gas
concentrations in the atmosphere at a level that would prevent
dangerous anthropogenic interference with the climate
system.’’ Furthermore, it was stated that ‘‘such a level
should be achieved within a time-frame sufficient to allow
ecosystems to adapt naturally to climate change, to ensure
that food production is not threatened and to enable economic
development to proceed in a sustainable manner.’’ There are
many debates on the question of which concentrations of
greenhouse gases can be regarded as being safe and which
conditions are required for achieving these stabilisation
levels, taking the resilience of ecosystems into account.
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M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
Several studies have tried to determine the temperature
increase corresponding to a level that would prevent major
anthropogenic interference with the climate system (IPCC,
2001a; Berk et al., 2001; O’Neill and Oppenheimer, 2002).
Outcomes of these studies show considerable uncertainty.
Specifying a level regarded as safe also involves political
choices. Here we avoid this debate by evaluating the
consequences of greenhouse gas stabilisation profiles that
remain within the limit of a global mean surface
temperature increase of 2 1C above the pre-industrial level,
as agreed upon by the European Union.
We have focused our analysis on the consequences for
European plant biodiversity and assessed whether the
climate goal of 2 1C is in line with biodiversity goals. In
April 2002, the Sixth Meeting of the Conference of Parties
to the Convention on Biological Diversity in The Hague
agreed on a strategic plan for the Convention. In the
mission statement, Parties commit themselves to ‘‘achieve
by 2010 a significant reduction of the current rate of
biodiversity loss at the global, regional and national level as a
contribution to poverty alleviation and to the benefit of all life
on earth’’ (CBD, 2002). This target was endorsed by the
World Summit on Sustainable Development (WSSD) (UN,
2002).
As with the UNFCCC target, the CBD target allows
multiple interpretations (for example, of what is a
significant reduction). For this reason, we used the EU
target, which is a stricter version of the CBD target, since
the European Ministers of Environment statement was ‘‘to
halt the loss of biological diversity at all levels by the year
2010’’ (UNECE, 2003). In order to measure whether the
halt of biodiversity loss could be realised in 2010, we would
need an indicator for loss of biodiversity. We started with
the list of indicators agreed upon in the Seventh
Conference of Parties in Kuala Lumpur, in which one of
them, the ‘‘trends in abundance and distribution of selected
species’’ we can use in investigating the status and trends of
the components of biological diversity (UNEP, 2004).
We have evaluated two mitigation scenarios that might
stay within the target range of the 2 1C above the preindustrial level (Eickhout et al., 2003). To assess the halt of
biodiversity loss for European plant species, we used
indicators close to the natural capital index (NCI) concept
applied in the third Global Environment Outlook (GEO3)
(UNEP, 2002). The NCI indicator reflects trends in
distribution of species. For the analysis we used the
Integrated Model to Assess the Global Environment
(IMAGE) (Alcamo et al., 1998; IMAGE team, 2001a) in
conjunction with an ecological model for European
vegetation, EUROMOVE (Bakkenes et al., 2002). The
IMAGE model was used for several global scenario
studies, such as the Special Report on Emissions Scenarios
(SRES) (Nakı́cenovı́c et al., 2000), GEO3 (UNEP, 2002)
and, very recently, the Millennium Ecosystem Assessment
(to be published in 2005). The EUROMOVE model was
also used in the study presented by Thomas et al. (2004) in
which the global consequences of climate change on
biodiversity were assessed. In view of uncertainties in the
expected climate change at a European level, we used
various climate patterns coinciding with the temperature
target. On the basis of our results and given the mitigation
strategies, we will show the long-term consequences for
biological diversity.
2. Methodology
2.1. Climate scenarios
We used a baseline scenario (Van Vuuren et al., 2003)
covering different characteristics of the IPCC’s SRES
(Nakı́cenovı́c et al., 2000) describing trends in the main
driving forces (population and economic growth), and
environmental pressures (emissions from energy, industrial
and land use) and their resulting effects, such as
temperature increase (Van Vuuren et al., 2003). The
population scenario assumes a global population stabilisation of 9.5 billion by 2100. On the economic side, the
baseline scenario describes a world in which globalisation
and technological development continue to be important
factors underlying economic growth, although not as
important as assumed in the IPCC A1b scenario (Nakı́cenovı́c et al., 2000).
The global greenhouse gas (GHG) emission trend (see
Fig. 1) of the baseline scenario—in the absence of climate
policies—leads to a global mean temperature increase of
more than 3 1C over pre-industrial levels by 2100. We used
two alternative global emission profiles for stabilising
GHG concentrations at 550 and 650 ppmv CO2 equivalent1
(S550e and S650e, respectively; see Fig. 1). We used these
stabilisation scenarios since both profiles can remain below
a global mean temperature increase of 2 1C with a low to
medium value of the climate sensitivity.2 Note, however,
that the S650e profile is unlikely to stay below this level,
unless the value of the climate sensitivity is at the low end
of the range (see Fig. 2 and Eickhout et al., 2003). In both
mitigation scenarios we implemented the Kyoto Protocol
until 2010.
To assess the consequences for ecosystems, the globalmean temperature change needs to be downscaled to local
levels where the behaviour of plants can be modelled.
General circulation models (GCMs) are currently the best
1
CO2-equivalent concentrations express the radiative forcing of all
greenhouse gases as the equivalent CO2 concentration resulting in a
similar forcing. We used the direct relation of each gas to its radiative
forcing for calculating the equivalent concentrations. From the sum of all
radiative forcings we can calculate the CO2-equivalent concentration.
Here, the Kyoto gases are included in the equivalent concentration: CO2,
CH4, N2O and the F gases. The stabilisation levels of 550 and 650 ppmv
CO2-equivalents are comparable with the respective CO2 concentration
levels of 450 and 550 ppmv.
2
The climate sensitivity (CS) is defined as the equilibrium global mean
surface temperature increase resulting from a doubling of CO2-equivalent
concentrations. Given the many uncertainties surrounding climate
sensitivity, the IPCC has defined a range from 1.5 to 4.5 1C with 2.5 1C
as the median value.
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M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
21
GHG Emissions (GtCO2-eq)
80
70
60
Baseline
50
40
IMAGE S650e
30
20
IMAGE S550e
10
0
1970
1990
2010
2030
2050
2070
2090
4
4
3.5
3.5
Global-mean T increase (degrees Celsius)
Global-mean T increase (degrees Celsius)
Fig. 1. Global emission profiles for stabilising GHG concentrations at 550 ppmv (IMAGE S550e) and 650 ppmv (IMAGE S650e) compared with baseline
emissions (Eickhout et al., 2003).
3
2.5
2
1.5
1
0.5
0
1970
1990
2010
2030
2050
2070
2090
3
2.5
2
1.5
1
0.5
0
1970
1990
2010
2030
2050
2070
2090
Fig. 2. Global-mean temperature increase since pre-industrial levels resulting from the IMAGE S550e (left panel) and IMAGE S650e (right panel) profiles
for different climate sensitivity assumptions (1.5, 2.5 and 4.5). The upper lines indicate the temperature increase resulting from CS ¼ 4.5; the lines in the
middle CS ¼ 2.5 and the bottom lines CS ¼ 1.5; the bold dashed line is the EU 2 1C target (Eickhout et al., 2003). For the rest of this study, we used a
climate sensitivity of 2.5 1C to assess the consequences of mitigation policies on biological diversity.
tools available for simulating the physical processes that
determine global climate dynamics and regional climate
patterns. We used different climate change patterns from
four GCM simulations and analysed the results with the
EUROMOVE model. Incorporation of the different
climate change patterns (temperature and precipitation
change) from the four GCMs leads to somewhat different
patterns of ecosystem shifts. The GCMs used are
HADCM-2 (Mitchell et al., 1995), ECHAM-4 (Bacher et
al., 1998), CGCM-1 (Boer et al., 2000), and CSIRO-MK12
(Hirst et al., 1996). Detailed information on the GCM
simulations can be found on the web site of the IPCC Data
Distribution Centre (www/ipcc-ddc.cru.uea.ac.uk/). The
differences in impacts are greater regionally than globally.
More details are given in IMAGE team (IMAGE team,
2001b), where results of different climate patterns for three
of the SRES scenarios are presented. The climate pattern of
HADCM-2 is used as default when results of EUROMOVE are shown.
2.2. Species response
We used the climatic patterns calculated for the three
model runs (baseline and its two related stabilisation
scenarios) to assess the new potential areas for occurrence
of different European vascular plant species, by using the
European plant-species model, EUROMOVE (Bakkenes et
al., 2002). EUROMOVE is a species-based logistic regression model by which occurrence probabilities can be
calculated for almost 1400 European vascular plant
species. The regression equations describe the relation
between six climatic variables provided by IMAGE and
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M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
species occurrence data from the Atlas Flora Europaeae
(AFE) (Jalas and Suominen, 1989; Ascroft, 1994). The
assumption for this regression model approach is that
broadscale species distributions are determined by and in
equilibrium with the prevailing climate. The model uses the
following climatic indicators: (i) temperature of the coldest
month; (ii) effective temperature sum above 5 1C; (iii) the
ratio between actual and potential evapotranspiration; (iv)
annual precipitation; (v) length of growing season and (vi)
mean growing season temperature above 5 1C. We selected
these variables, by using a principal component analysis,
from a total of 14 climatic variables that are commonly
used in different species models (Bakkenes et al., 2002).
With these data we can make predictions of occurrence
probability maps for 1397 plant species based on the
climate variables provided by the IMAGE model.
To construct the current and future plant species’
distribution patterns we need to transform the calculated
occurrence probabilities into present-absent data. We have
done this by calculating a threshold probability value for
each species that maximises the similarity between modelled species occurrence and species occurrence according
to the AFE. The k statistics (Cohen, 1960; Monserud and
Leemans, 1992) served as the similarity index between the
estimated map and the distribution map derived from the
AFE. We used only species for which the correspondence
between the current estimated distribution and the
distribution according to the AFE was fair to good
(k40:4). This resulted in using 856 out of the 1397
modelled plant species in EUROMOVE. Species distributions were estimated on a grid with cells of approximately
2500 km2 for the current (1995) and future situations (2025,
2050 and 2100) for each of the three scenarios and the four
regional climate patterns (GCMs). This allowed us to
calculate the number of species for each grid cell for which
climate remains suitable in the future, the number of
species for which the climate may become unsuitable and
the number of species for which climate may become newly
suitable. We expressed these figures relative to the number
of species present in 1995. Subsequently the future
distribution area of each species was compared with the
current distribution, so that the stable area, the area that
may become suitable, and the area where the species is
likely to disappear can be estimated. The mean stable area
relative to the current distribution areas for all species can
be regarded as a measure for conservation of biodiversity.
By aggregating these results per European country and
Europe in total, this indicator serves as a proxy for
biodiversity loss in Europe. The indicator is therefore
closely related to the indicator suggested by the CBD and
the European biodiversity objective. The closer the stable
area is to 100%, the more the forecast species distribution
reflects the original modelled distribution. A drawback of
the stable area indicator is that it only indicates how much
of the current state is preserved in the future but does not
give information about new suitable area. Use of this
indicator allows us to address the issue on whether the
target of slowing down the species decline will be met.
Contrary to the analysis in Bakkenes et al. (2002) we
excluded the Russian Federation, the Belarus, the Ukraine,
the Republic of Moldova and Turkey from our study area
because of the relatively poor sampling frequency for these
regions.
3. Biodiversity results for different stabilisation levels
Here, we present the biodiversity results for the baseline
and focus on the impacts of climate stabilisation policies
for the European plant species. The effects of climate
change on the stable area according to the baseline scenario
are considerable (Table 1).
Focusing on the year 2010, in only 1% of the cells will
the species composition remain identical to today’s count.
However, with respect to climatic implications, the effects
on plant species will increase after 2010. Climate policies up
to 2010 (i.e. the Kyoto Protocol) are not sufficient to
decrease the loss of biodiversity, let alone to halt this loss.
This result allows us to conclude that the biodiversity
objectives of the EU will not be met in 2010, taking only
climate change into consideration.
Table 1
Biodiversity changes in Europe in the baseline scenario (Van Vuuren et al.,
2003) for the year 2100 showing net species flux, stable location area of
species and number of disappearing species in 20 European regions with
respect to 1995
Region
# species Stable
in 1995a area
Ireland and Great
Britain
Iceland
Spitsbergen
Norway and Sweden
Finland
Baltic States
Poland
Czech Republic,
Slovakia and Hungary
Romania and Bulgaria
Slovenia, Croatia,
Serbia & Montenegro,
Bosnia & Herzegovina,
Macedonia and
Albania
Greece
Italy
Spain and Portugal
France
Benelux
Germany
Switzerland and
Austria
Denmark
387
0.83
31
70
254
34
451
241
278
398
430
0.86
0.86
0.86
0.86
0.90
0.76
0.69
21
4
14
13
25
41
40
55
39
159
139
85
68
84
536
637
0.47
0.57
56
41
80
58
595
702
601
592
318
468
511
0.60
0.60
0.51
0.69
0.84
0.80
0.76
149
51
53
64
33
57
30
62
39
105
32
53
66
69
307
0.86
36
42
846
0.71
9
8
Europe
#
disappearing
#
appearing
a
Number of species calculated by EUROMOVE from the total number
of species modelled by EUROMOVE (1397, for this study we used only
856 species), this is not the actual number of species for each region.
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After 2010, we assume that more stringent climate
policies will be implemented and that the climatic results of
the baseline and the two stabilisation scenarios will begin
to diverge. In the year 2050 the species composition in the
baseline scenario will change in each location. Only 3% of
the species are robust enough to withstand the forecasted
climate change and show no decline in their current
distribution area. The stable area in the baseline scenario
will decline from 92% in 2025 to 84% and 71% in 2050 and
2100, respectively. Many species will disappear from each
country because of climate change (Table 1). In Europe as
a whole nine plant species will have disappeared by the end
of this century, showing the need for climate mitigation
policies if European biodiversity objectives are to be
realised.
In Table 2 we observe a significant improvement in the
stable area indicator if we compare the results from the
baseline scenario with the results from the two stabilisation
scenarios. The difference between the two stabilisation
scenarios only starts to diverge after 2050 because of inertia
in the climate system. The difference between the two
stabilisation scenarios will become larger after 2100, since
the S650e scenario will reach its stabilisation level after
2100 (see Table 2).
The impact of climate change on the plant species
community is not the same for all regions (Table 2), with
the regions most affected being countries like Romania and
23
Bulgaria, Spain and Portugal, Former Yugoslavia and
Albania, Greece, and Italy. For the baseline scenario these
regions show a decline in stable area of about 20–30% in
2050, and 40–50% in 2100. Some regions, like the Baltic
States, Iceland, the Benelux (Belgium, The Netherlands
and Luxembourg), and the Scandinavian countries, are less
sensitive to climate change with respect to their stable area.
The impact on their stable areas lies within 10% in 2050
and 20% in 2100 for the baseline scenario. However a 20%
decline in stable area will still have a very considerable
impact on the species composition.
Logically, the positive effect on biodiversity of the
different stabilisation scenarios with respect to the baseline
scenario is the largest in the regions with the largest
impacts (Table 2). Nevertheless, even with strict climate
mitigation strategies resulting in higher probabilities for
attaining the European climate target of 2 1C, the loss of
biodiversity per European country remains. A coherent
European biodiversity policy, in conjunction with strict
global climate mitigation, might ensure that the goal of
halting biodiversity loss is met by the end of this century,
instead of by 2010.
Other biodiversity indicators return regional results
comparable to those returned by the stable area indicator.
Table 1 shows a high positive species flux (more
‘‘immigrating’’ species than ‘‘emigrating’’ species) calculation for the northern countries like Finland, Norway,
Table 2
Biodiversity changes in Europe in 2025, 2050 and 2100 with respect to 1995, showing fraction of stable location for the baseline and GHG stabilisation
scenarios (Eickhout et al., 2003) in 20 European regions
Region
# in 1995
2025
2050
2100
Baseline
S650e
S550e
Baseline
S650e
S550e
Baseline
S650e
S550e
Ireland and Great Britain
Iceland
Spitsbergen
Norway and Sweden
Finland
Baltic States
Poland
Czech Republic, Slovakia and
Hungary
Romania and Bulgaria
Slovenia, Croatia, Serbia &
Montenegro, Bosnia &
Herzegovina, Macedonia and
Albania
Greece
Italy
Spain and Portugal
France
Benelux
Germany
Switzerland and Austria
Denmark
387
254
34
451
241
278
398
430
0.95
0.98
0.95
0.97
0.97
0.99
0.97
0.92
0.96
0.98
0.95
0.97
0.97
0.99
0.97
0.93
0.96
0.98
0.95
0.97
0.97
0.98
0.96
0.92
0.91
0.95
0.90
0.93
0.94
0.97
0.91
0.82
0.92
0.96
0.91
0.94
0.95
0.97
0.93
0.85
0.91
0.95
0.92
0.94
0.94
0.96
0.92
0.84
0.83
0.86
0.86
0.86
0.86
0.90
0.76
0.69
0.88
0.92
0.89
0.90
0.90
0.94
0.85
0.76
0.89
0.94
0.91
0.91
0.91
0.95
0.88
0.80
536
637
0.82
0.86
0.83
0.87
0.83
0.86
0.66
0.72
0.70
0.76
0.70
0.76
0.47
0.57
0.58
0.66
0.63
0.71
595
702
601
592
318
468
511
307
0.85
0.90
0.84
0.93
0.97
0.96
0.94
0.97
0.86
0.90
0.85
0.94
0.97
0.96
0.94
0.97
0.86
0.90
0.85
0.94
0.97
0.96
0.94
0.97
0.73
0.78
0.70
0.86
0.93
0.90
0.86
0.94
0.76
0.82
0.74
0.88
0.94
0.92
0.88
0.94
0.75
0.81
0.74
0.88
0.94
0.91
0.88
0.94
0.60
0.60
0.51
0.69
0.84
0.80
0.76
0.86
0.67
0.71
0.62
0.80
0.90
0.86
0.81
0.91
0.71
0.76
0.68
0.84
0.92
0.88
0.85
0.92
Europe
Minimum
Maximum
846
0.92
0.82
0.99
0.93
0.83
0.99
0.92
0.83
0.98
0.84
0.66
0.97
0.86
0.70
0.97
0.86
0.70
0.96
0.71
0.47
0.90
0.78
0.58
0.94
0.82
0.63
0.95
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M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
Fig. 3. Results for stable area per grid cell, using the HADCM-2 model for the three analysed scenarios: baseline, S650e, and S550e. Results are for 2100
compared to the situation in 1995.
Sweden and the Baltic States. Much lower or, sometimes,
even negative fluxes are found in the southern regions. The
negative species flux for the southern countries can be
partly explained by the fact that the northern African
species (potential ‘‘new’’ species in Spain, for example) are
not included in the EUROMOVE model. As shown by Fig.
3, there is also variation in stable area within regions.
Concluding, the baseline scenario will not lead to a
reduction in the rate of biodiversity loss. This result
confirms the need for implementation of stabilisation
scenarios to achieve the goal of halting biodiversity loss
and approach the target set by the WSSD and CBD.
However, beneficial results are not expected before 2050
because of inertia in the climate system, indicating the
impossibility to reach a halt of biodiversity loss before the
end of this century.
the results we also analysed the biodiversity shifts for
different regional disaggregations of the climate pattern for
the baseline and the two stabilisation scenarios. The results
from HADCM-2 are comparable with ECHAM-4 and lead
to higher changes in species shifts than the results based on
the regional projections from the GCMs CGCM and
CSIRO-MK2.
Although there are differences between the different
GCMs there is also ‘‘consensus’’ between the different
GCM models about the regions that are most vulnerable to
climate change and the regions that are less vulnerable.
This is also the case for the different scenarios. We find
Romania and Bulgaria, Spain and Portugal, Italy and
Former Yugoslavia and Albania among the most vulnerable regions. The more stable regions or the regions with
less climate change are in Denmark, the Benelux, Iceland,
and the Baltic States.
3.1. Robustness of results
4. Conclusions and discussion
The above-mentioned results are all based on the GCM
of the Hadley Centre (HADCM-2). Other GCMs produce
a different regional pattern for the same mean climate
change (see Fig. 4 and Table 3). To test the robustness of
In our analysis of the consequences of climate change for
biodiversity in Europe, we found that in the absence of any
global mitigation it is very likely that a significant
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25
Fig. 4. Regional variation in 2100 in the stable area in the baseline climate scenario for the four different GCMs.
Table 3
Effects of different global circulation models (GCMs) on average stable area and regional distribution of the region with maximum and minimum changes
of biodiversity for 2025, 2050 and 2100
Year
Baseline
S650e
S550e
HADCM2 ECHAM CSIRO CGCM HADCM2 ECHAM CSIRO CGCM HADCM2 ECHAM CSIRO CGCM
2025 # disappearing
Stable area
Minimum
Maximum
3
0.92
0.82
0.99
6
0.93
0.84
0.98
4
0.95
0.89
0.98
3
0.95
0.88
0.99
3
0.93
0.83
0.99
5
0.93
0.84
0.98
4
0.95
0.90
0.98
3
0.95
0.89
0.98
2
0.92
0.83
0.98
5
0.93
0.84
0.98
4
0.95
0.90
0.98
3
0.95
0.88
0.99
2050 # disappearing
Stable area
Minimum
Maximum
7
0.84
0.66
0.97
7
0.84
0.68
0.95
6
0.88
0.79
0.95
5
0.89
0.76
0.98
6
0.86
0.70
0.97
6
0.87
0.73
0.96
5
0.90
0.81
0.96
4
0.90
0.79
0.96
3
0.86
0.70
0.96
5
0.86
0.73
0.96
5
0.89
0.80
0.96
4
0.90
0.79
0.98
2100 # disappearing
Stable area
Minimum
Maximum
9
0.71
0.47
0.90
15
0.70
0.49
0.89
12
0.77
0.63
0.89
8
0.78
0.60
0.95
8
0.78
0.58
0.94
12
0.79
0.61
0.93
9
0.84
0.72
0.93
4
0.84
0.69
0.93
8
0.82
0.63
0.95
7
0.82
0.67
0.94
9
0.86
0.76
0.94
4
0.86
0.74
0.96
proportion (averaging 10%) of plant species will disappear
from many European countries by 2100. Even in Europe
(all analysed countries combined), 1% of the plant species
will become extinct because there will no longer be a
suitable climate niche for these plant species. The number
of species that become extinct may increase if species
cannot migrate to new, suitable areas within the time frame
of the scenarios or when they are out-competed by new
ARTICLE IN PRESS
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M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
invasive species. The European climate policy up to 2010
(the Kyoto Protocol) will not have an effect on climate
change before 2025 and is likely to be insufficient to
stabilise the climate after 2100. We therefore conclude that
the European objective of a ‘‘halt to biodiversity loss’’ in
2010 is out of reach. Even if very ambitious policy
measures are taken and a temperature increase below the
global 2 1C increase compared to preindustrial levels is
likely (European climate objective), 5–35% of the plant
species will still disappear from several European countries.
Hence, the European biodiversity target for a halt to
biodiversity loss will not be met if each country is measured
separately. For Europe as a whole, this biodiversity target
will be within reach by the end of this century, when very
strict mitigation strategies are taken, provided that no
other threat on biodiversity is allowed to increase and
assuming that species can easily migrate between areas
having suitable climate. In other words, this combined
assessment of the potential effect of climate and biodiversity policies endorses the European policy to set the
stabilisation target at 2 1C above pre-industrial level as a
maximum increase to potentially achieve a halt to
biodiversity loss in Europe. However, reaching this target
in 2010 is likely to be impossible. To facilitate species
migration and preservation strict mitigation strategies are
needed to be accompanied by a coherent European view on
nature corridors, with enough flexibility to accommodate
uncertainty in the local climatic consequences.
Our analysis has made it clear that species composition
will change in every part of Europe in a different way. The
most dramatic changes will occur in Northern Europe,
where more than 35% of the species composition in 2100
will be invasive, and in Southern Europe, where up to 25%
of the species now present will have disappeared under the
climatic circumstances forecasted for 2100. The predicted
shift of species is in line with recent observations showing
increases in occurrence and abundance of thermophilic
(heat-demanding) species and a small decrease in traditionally cold-tolerant species in the Netherlands and
Norway, and in the United Kingdom (EEA, 2004; Preston
et al., 2002). Similar observations are available for other
species groups. Parmesan and Yohe (2003) found (in a
meta-analysis) many butterfly, bird and lichen species to
show a northward shift consistent with climate change. All
these findings confirm the possible impact of climate
change on the distribution of species.
It is expected that our results have their parallels in other
regions. Many studies, using models from different parts of
the world, suggest similar expected patterns (Thomas et al.,
2004; Townsend et al., 2002; Beaumont and Hughes, 2002;
Midgley et al., 2002; Erasmus et al., 2002).
Thomas et al. (2004) calculated that if unrestricted
migration is assumed, 3–6% of the endemic European
plant species will be committed to extinction by 2050. They
used a ‘‘species–area’’ relationship for the estimation of
that figure. Our calculation shows that for 1% of the
species a suitable climate will not be available in 2100, and
that these species might become extinct in the baseline
scenario with the assumption of complete migration.
Applying the same calculation method as Thomas et al.
(2004) gives us the same number if migration is assumed
and only a slightly different number if no migration is
assumed.3 The difference in outcome is probably because
we used 856 species in this study compared to 1397 in the
Thomas et al. (2004) study; therefore we also have fewer
endemic species (104 instead of 192).
There is evidence of climate induced extinctions in the
late Pleistocene (Barnosky et al., 2004). Although in most
cases climate change in combination with human impact
was playing a role in the extinction. Apart from the Golden
toad, Bufo periglenes, from Costa Rica (Pounds and
Puschendorf, 2004) there is no clear evidence of recent
historic species extinction with climate as the main driving
force, and whether this will remain so in the future is
unknown. But there is evidence describing phenological
changes related to climate change (Roy and Sparks, 2000;
Both and Visser, 2001; Peñuelas et al., 2002). Some recent
observations (Pimm, 2001; Thomas et al., 2001; McCarty,
2001; Walther et al., 2002; Root et al., 2003; Walther et al.,
2005) confirm that some species are already migrating, if
they can and will keep pace with the current rate of climate
change is unclear. Walther et al. (2005) relate the migration
of the Ilex aquifolium species with the advancing 0 1C
January-isoline. Williams et al. (2002) stated that during
the Younger Dryas event (12,900–11,500 years BP)
vegetation responded in less than 100–200 years to a very
rapid cooling event—average temperature in the North
Atlantic region abruptly took a downward plunge by
nearly 5 1C. It is therefore not unlikely that many species
have the potential to respond quickly to climate change
and can migrate fast enough to keep up with the projected
change of climate. But migration will only be possible if
suitable pathways are present. In the fragmented European
landscape, migrating species will encounter many obstacles
and barriers for their migration. This will slow down
migration and might even prevent the invasion of species in
new suitable area. Policy towards the realisation of a
European-wide network of ecosystems (EC, 1992) is
therefore necessary if the biodiversity objective is to remain
valid.
The calculated effects of climate change are only based
on average climate characteristics; timing, extremes and
amplitude are not taken into account. The results of this
study are therefore not complete. Many uncertain responses can be expected to occur, at least on local scales if,
for example, drought periods are extremely long or if
rainfall is concentrated into a few weeks instead of months.
We expect these extreme events possibly to worsen the
3
In the no migration option, Thomas et al. (2004) showed the
percentage of species commited to extinction to be 10%, 13% and 16%,
respectively for the three different methods of calculating extinction risk
when using a ‘‘species–area’’ relation. In our study we calculated
percentages of 9%, 13% and 16%.
ARTICLE IN PRESS
M. Bakkenes et al. / Global Environmental Change 16 (2006) 19–28
effects in most cases, thus underlining the importance of
stabilising global CO2 concentrations and additional
biodiversity management. It will be important to determine
new biodiversity objectives after 2010 in conjunction with
other environmental policies, especially with post-Kyoto
climate policies.
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