188
Planning for persistence in a changing world
included by ensuring sequential connectivity between
present and future ranges. The limitation of the
approach is that it assumes we are confi dent with our
distribution predictions, and it invariably suggests that
we need to conserve unreasonably large fractions of a
region. It is thus not particularly realistic.
A more holistic approach that is gaining popularity
in policy is to concentrate conservation efforts in
continental - scale corridors. Many recent initiatives
around the world have called for increases in connectivity with various corridor and linkage projects based
on arguments concerning climate change impacts
(Soul é et al. , 2004 ; Mackey et al. , 2008 ; Pearce et al. ,
2008 ). Such large - scale projects beg two questions.
First, why is concentrating efforts to provide connectivity in one broad corridor better than scattering
those investments more widely across the landscape?
What would happen if we took the investment that is
going into restoration and land management and disperse it thinly across the same region? The case for
reconstructing (or maintaining and improving) one
broad corridor at a large spatial scale relies on a belief
that the whole is more than the sum of the parts – that
several spatially connected investments deliver a
greater outcome than those investments in isolation. Is
this belief true? This is a big question – a critical landscape scale question – that is worth testing (see further
discussion of fragmentation effects and corridors in
Chapter 8 ).
Second, if we assume that large - scale connectivity is
critical to species and habitat persistence in the long
term under climate change, where is the optimal location for connectivity corridors? So far there have been
no global - scale or continental - scale analyses of the best
options of where to restore continental - scale connectivity. Such an undertaking would need to include information addressing questions such as the following:
1 Along which gradients (temperature, rainfall, latitude, elevation) are shifts in range due to climate
change most likely to occur?
2 How will other threats change with climate change?
(e.g. see Box 7.5 )
3 Where is a continental - scale corridor most likely to
succeed for social, economic and political reasons?
4 Where is a continental - scale corridor likely to deliver
most leverage from other fi nancial sources?
5 How much will it cost and what are the expected
benefi ts in the long - term and short - term?
6 What monitoring is required to determine whether
it is all worthwhile?
7 What is likely to be the fate of these areas if we do
not invest in them?
If continental - scale connectivity is impossible or
fails, what other actions can we take to maintain biodiversity in a world that is being impacted by rapid
climate change? One of the most controversial proposals is ‘ assisted colonization ’ – moving species beyond
their historical ranges to places where we think the
climate will suit them in the future (Hoegh - Guldberg
et al. , 2008 ). This means introducing a species into a
place where it has not been recently, or ever, which
carries risks similar to any introduction of a species
beyond its current native range (Simberloff, 2001 ).
Assisted colonization is ecologically risky and normally expensive, and we have yet to determine its
expected costs and benefi ts. This is an urgent scientifi c
challenge in a situation where it may remain our
only option, but where the legislative, political and
social system is not in place to ensure successful
implementation.
7.5 CLOSING REMARKS
Biodiversity then, is changing continuously over time.
Conservation must therefore hit a moving target, so
planning only for present - day patterns could lead to
ineffi cient use of resources. Long - term ecology has
revealed that biodiversity is highly dynamic, even over
relatively short timescales. Species ’ geographical
ranges expand and contract, and multiple threats can
act in concert to bring about sharp declines in once
common species.
Modelling techniques are available to attempt to
build predictions about future change, on which conservation plans can be based. However, these models
are beset with uncertainty, producing future scenarios
that can differ enormously depending on the assumptions made and the methods used. The practical challenge now is to establish spatial conservation plans
that are robust to this uncertainty.
FOR DISCUSSION
1 What are the key challenges involved in modelling
future species ’ distributions for the latter part of the
21st century?
Planning for persistence in a changing world
included by ensuring sequential connectivity between
present and future ranges. The limitation of the
approach is that it assumes we are confi dent with our
distribution predictions, and it invariably suggests that
we need to conserve unreasonably large fractions of a
region. It is thus not particularly realistic.
A more holistic approach that is gaining popularity
in policy is to concentrate conservation efforts in
continental - scale corridors. Many recent initiatives
around the world have called for increases in connectivity with various corridor and linkage projects based
on arguments concerning climate change impacts
(Soul é et al. , 2004 ; Mackey et al. , 2008 ; Pearce et al. ,
2008 ). Such large - scale projects beg two questions.
First, why is concentrating efforts to provide connectivity in one broad corridor better than scattering
those investments more widely across the landscape?
What would happen if we took the investment that is
going into restoration and land management and disperse it thinly across the same region? The case for
reconstructing (or maintaining and improving) one
broad corridor at a large spatial scale relies on a belief
that the whole is more than the sum of the parts – that
several spatially connected investments deliver a
greater outcome than those investments in isolation. Is
this belief true? This is a big question – a critical landscape scale question – that is worth testing (see further
discussion of fragmentation effects and corridors in
Chapter 8 ).
Second, if we assume that large - scale connectivity is
critical to species and habitat persistence in the long
term under climate change, where is the optimal location for connectivity corridors? So far there have been
no global - scale or continental - scale analyses of the best
options of where to restore continental - scale connectivity. Such an undertaking would need to include information addressing questions such as the following:
1 Along which gradients (temperature, rainfall, latitude, elevation) are shifts in range due to climate
change most likely to occur?
2 How will other threats change with climate change?
(e.g. see Box 7.5 )
3 Where is a continental - scale corridor most likely to
succeed for social, economic and political reasons?
4 Where is a continental - scale corridor likely to deliver
most leverage from other fi nancial sources?
5 How much will it cost and what are the expected
benefi ts in the long - term and short - term?
6 What monitoring is required to determine whether
it is all worthwhile?
7 What is likely to be the fate of these areas if we do
not invest in them?
If continental - scale connectivity is impossible or
fails, what other actions can we take to maintain biodiversity in a world that is being impacted by rapid
climate change? One of the most controversial proposals is ‘ assisted colonization ’ – moving species beyond
their historical ranges to places where we think the
climate will suit them in the future (Hoegh - Guldberg
et al. , 2008 ). This means introducing a species into a
place where it has not been recently, or ever, which
carries risks similar to any introduction of a species
beyond its current native range (Simberloff, 2001 ).
Assisted colonization is ecologically risky and normally expensive, and we have yet to determine its
expected costs and benefi ts. This is an urgent scientifi c
challenge in a situation where it may remain our
only option, but where the legislative, political and
social system is not in place to ensure successful
implementation.
7.5 CLOSING REMARKS
Biodiversity then, is changing continuously over time.
Conservation must therefore hit a moving target, so
planning only for present - day patterns could lead to
ineffi cient use of resources. Long - term ecology has
revealed that biodiversity is highly dynamic, even over
relatively short timescales. Species ’ geographical
ranges expand and contract, and multiple threats can
act in concert to bring about sharp declines in once
common species.
Modelling techniques are available to attempt to
build predictions about future change, on which conservation plans can be based. However, these models
are beset with uncertainty, producing future scenarios
that can differ enormously depending on the assumptions made and the methods used. The practical challenge now is to establish spatial conservation plans
that are robust to this uncertainty.
FOR DISCUSSION
1 What are the key challenges involved in modelling
future species ’ distributions for the latter part of the
21st century?