184
Planning for persistence in a changing world
habitat type or species, they chose a suite of sites that
give a suffi ciently high probability that a conservation
target is met. For example, if we know the chance that
each reef of a particular type will be severely impacted
by a hurricane, and how fast it can recover, we can
determine how many reefs of that type need to be conserved to be 95 per cent sure that at least three are in
a healthy state at any point in time.
that possess a given biodiversity attribute to ensure
resilience of the conservation network?).
It is thus common practice in conservation planning
to avoid highly threatened sites, except where they
contain unique features. Game et al . (2008) have
shown how to include the risk of catastrophic events
in coral reef reserve selection. Here, instead of aiming
to conserve a fi xed number of representatives of a
Box 7.4 Long - t erm e cological i nsights into d ynamic c onservation p lanning
Studying the changes in plant and animal communities during past periods of climate upheaval may
provide important clues to how contemporary communities will react to the rapid pace and high
magnitude of anthropogenic climate change forecast for the 21st century. The onset of the present
interglacial, the Holocene, provides one such analogue period, of rapid and dramatic climate forcing.
Bush (2002) has reviewed the responses of the vegetation of the Andean fl ank of Peru during this
period, when temperatures rose by an estimated 5 – 9 ° C (Colinvaux & De Oliveira, 2000 ). At fi rst sight,
this might suggest that the fl ora should be capable of withstanding another rapid warming event.
However, Bush (2002) cautions against this simplistic interpretation for two reasons:
i the current fl ora have spent the last two million years in cooler - than - modern conditions and may
therefore be close to their upper thermal limits;
ii humans have dramatically altered the landscape since the Holocene, which may both exacerbate
climate change and also prevent or restrict species from migrating to new areas.
In the case of the Andean fl ank, the frost line and the cloud base are predicted to rise higher
(perhaps 600 m this century) up mountainsides. Based on the patterns at the transition into the
Holocene, when non - analogue pollen assemblages occurred, we may expect species to respond
individualistically to this forcing. Upslope migration of species, especially those with narrow elevational ranges, is anticipated in response to climate change, although the migration of species from
the lowest elevations will be severely compromised by the abundant agricultural land that now exists
between about 800 m and 1500 m above sea level in many areas. The habitat islands of forest that
remain may no longer provide habitats suitable for lower montane species, and considerable species
turnover could thus lead to new and often lower - diversity assemblages. Moreover, species that
currently inhabit the lowest limit of the cloud forest may not be able to migrate as fast as local
agriculturalists who are keen to exploit the newly available agricultural land.
Bush (2002) concludes by arguing that the lesson of palaeoecology is that conservation must aim
to maintain plant and animal niches and the possibility for species to respond individualistically,
rather than focusing on conserving current communities. The greatest challenge will be maintaining
enough habitat for critical ecosystems, such as cloud forest, and ensuring that remaining fragments
are linked up to allow migrations. Conservation efforts should also be focused on the protection of
lower cloud forest regions of tropical mountains as a means to mitigate anticipated habitat loss, and
as a means of giving species a chance to migrate.
By integrating an assessment of a past episode of extreme climate change with a consideration
of current patterns of human activity in the region, Bush ’ s paper points to the importance of taking
account of both forms of insight in modelling future climate change impacts. For an illustration of
how future changes in land use might be incorporated at least for heuristic purposes in systematic
conservation assessments, see Box 7.5 .
Planning for persistence in a changing world
habitat type or species, they chose a suite of sites that
give a suffi ciently high probability that a conservation
target is met. For example, if we know the chance that
each reef of a particular type will be severely impacted
by a hurricane, and how fast it can recover, we can
determine how many reefs of that type need to be conserved to be 95 per cent sure that at least three are in
a healthy state at any point in time.
that possess a given biodiversity attribute to ensure
resilience of the conservation network?).
It is thus common practice in conservation planning
to avoid highly threatened sites, except where they
contain unique features. Game et al . (2008) have
shown how to include the risk of catastrophic events
in coral reef reserve selection. Here, instead of aiming
to conserve a fi xed number of representatives of a
Box 7.4 Long - t erm e cological i nsights into d ynamic c onservation p lanning
Studying the changes in plant and animal communities during past periods of climate upheaval may
provide important clues to how contemporary communities will react to the rapid pace and high
magnitude of anthropogenic climate change forecast for the 21st century. The onset of the present
interglacial, the Holocene, provides one such analogue period, of rapid and dramatic climate forcing.
Bush (2002) has reviewed the responses of the vegetation of the Andean fl ank of Peru during this
period, when temperatures rose by an estimated 5 – 9 ° C (Colinvaux & De Oliveira, 2000 ). At fi rst sight,
this might suggest that the fl ora should be capable of withstanding another rapid warming event.
However, Bush (2002) cautions against this simplistic interpretation for two reasons:
i the current fl ora have spent the last two million years in cooler - than - modern conditions and may
therefore be close to their upper thermal limits;
ii humans have dramatically altered the landscape since the Holocene, which may both exacerbate
climate change and also prevent or restrict species from migrating to new areas.
In the case of the Andean fl ank, the frost line and the cloud base are predicted to rise higher
(perhaps 600 m this century) up mountainsides. Based on the patterns at the transition into the
Holocene, when non - analogue pollen assemblages occurred, we may expect species to respond
individualistically to this forcing. Upslope migration of species, especially those with narrow elevational ranges, is anticipated in response to climate change, although the migration of species from
the lowest elevations will be severely compromised by the abundant agricultural land that now exists
between about 800 m and 1500 m above sea level in many areas. The habitat islands of forest that
remain may no longer provide habitats suitable for lower montane species, and considerable species
turnover could thus lead to new and often lower - diversity assemblages. Moreover, species that
currently inhabit the lowest limit of the cloud forest may not be able to migrate as fast as local
agriculturalists who are keen to exploit the newly available agricultural land.
Bush (2002) concludes by arguing that the lesson of palaeoecology is that conservation must aim
to maintain plant and animal niches and the possibility for species to respond individualistically,
rather than focusing on conserving current communities. The greatest challenge will be maintaining
enough habitat for critical ecosystems, such as cloud forest, and ensuring that remaining fragments
are linked up to allow migrations. Conservation efforts should also be focused on the protection of
lower cloud forest regions of tropical mountains as a means to mitigate anticipated habitat loss, and
as a means of giving species a chance to migrate.
By integrating an assessment of a past episode of extreme climate change with a consideration
of current patterns of human activity in the region, Bush ’ s paper points to the importance of taking
account of both forms of insight in modelling future climate change impacts. For an illustration of
how future changes in land use might be incorporated at least for heuristic purposes in systematic
conservation assessments, see Box 7.5 .