168
Planning for persistence in a changing world
passenger pigeon, can sometimes decline rapidly to
extinction (Gaston & Fuller, 2008 ).
Sometimes the story is much less clear and detailed
historical analysis is necessary to piece together and
learn from past events. For example, the Allegheny
woodrat ( Neotoma magister ) was formerly widespread
across the Appalachian mountains of the north - east
USA. In the 1970s it began disappearing from the
northern part of its range, and only a decade later it
was extinct in New York, Connecticut and much of
New Jersey, and threatened in Maryland, Ohio,
Pennsylvania and Indiana (Hicks, 1989 ). There is no
obvious single cause of this decline; the species is not
exploited, its habitat remains more or less intact, and
there are no (known) introduced predators or competitors that appear to be responsible for the decline.
A careful analysis of historical information by
LoGiudice (2006) , beginning with observations in the
19th century literature, uncovered a story of ‘ death by
a thousand cuts ’ that had begun long before the decline
was apparent to wildlife biologists. A series of small
anthropogenic threats, from habitat fragmentation to
introduced tree pathogens, each in themselves insuffi -
cient to cause the decline, had occurred sequentially,
resulting in eventual wholesale disappearance of the
species from a large part of its historical range.
LoGiudice (2006) ends with a plea to conservation scientists: ‘ We must train ourselves to look broadly (in the
ecological sense) and deeply (in the historical sense)
when investigating the causes of species declines. ’
Where long - term information is not available, this
does not mean that we are unable to act. While it is
useful to have the knowledge to make sensible predictions about which conservation interventions will be
successful, it is critical not to let action become delayed
by focusing exclusively on accumulating knowledge
about a particular problem or system. Recent developments in decision theory allow estimates about how a
system works to be updated as new information
becomes available, thus, over time, improving the likelihood of success of conservation action without
unnecessarily delaying action just because knowledge
is incomplete (for a review, see Grantham et al. , 2010 ).
This is particularly important where there are many
possible reasons for a particular observed decline or, as
in the case of the Allegheny woodrat, where a decline
is driven by many small effects acting in concert. A
detailed historical analysis of past declines can take
place alongside, and eventually guide, contemporary
conservation efforts.
7.2.1 Predicting f uture e cosystem
r esponses to c hanging c onditions
Despite the long history of human intervention, conservation theory and practice generally focus on how
present conditions, both natural and anthropogenic,
determine species ’ distributions and abundances. This
is consistent with the notion that conservation is a
crisis discipline in which we must act before knowing
all the facts (Soul é , 1985 ). For example, according to
the IUCN ’ s Red List, some 22 per cent of vertebrates are
threatened with imminent extinction (IUCN, 2008 ).
Action to enhance their chances of persistence is
urgent, although investment thus far has been limited
(Bottrill et al. , 2008 ).
Processes have generated and shaped the patterns
that we see as a fl eeting snapshot today, and processes
are the rules that govern how ecosystems will respond
to future changes. A fi rst key contribution of long - term
ecology to conservation, then, is that palaeoecological
and historical data can help unravel these rules; the
way that ecosystems and species responded to past
changes might tell us something about how they will
react in the future to management or threat.
In some cases, the story of a decline and, thus, the
conservation intervention required to reverse that
decline, is clear. For example, the ban on trade in ivory
of African elephants, introduced in 1989, successfully
led to recovery of the population, although there are
still hotspots of continuing trade and elephants are still
declining rapidly in some places (Stiles, 2004 ; Lemieux
& Clarke, 2009 ).
Sometimes, the cause of population declines is a
combination of natural variability and changing levels
of harvesting, such that the appropriate policy response
is much less certain. For example, more than ten
million tonnes of Peruvian anchovetta ( Engraulis
ringens ) were harvested in some years before the stock
collapsed in the early 1970s. The collapse was apparently brought about by a combination of the level of
exploitation and natural population variability in the
Peruvian upwelling system. The decline persisted into
the mid - 1980s, when the population began a period of
increase towards its earlier levels before collapsing
again during the late 1990s. Because the balance
between supply and demand effects remains uncertain,
policy decisions relating to this fi shery are diffi cult
(Pontecorvo, 2001 ). However, long - term data are critical in explaining fl uctuations in such fi sheries, and
history shows us that common species, such as the
Planning for persistence in a changing world
passenger pigeon, can sometimes decline rapidly to
extinction (Gaston & Fuller, 2008 ).
Sometimes the story is much less clear and detailed
historical analysis is necessary to piece together and
learn from past events. For example, the Allegheny
woodrat ( Neotoma magister ) was formerly widespread
across the Appalachian mountains of the north - east
USA. In the 1970s it began disappearing from the
northern part of its range, and only a decade later it
was extinct in New York, Connecticut and much of
New Jersey, and threatened in Maryland, Ohio,
Pennsylvania and Indiana (Hicks, 1989 ). There is no
obvious single cause of this decline; the species is not
exploited, its habitat remains more or less intact, and
there are no (known) introduced predators or competitors that appear to be responsible for the decline.
A careful analysis of historical information by
LoGiudice (2006) , beginning with observations in the
19th century literature, uncovered a story of ‘ death by
a thousand cuts ’ that had begun long before the decline
was apparent to wildlife biologists. A series of small
anthropogenic threats, from habitat fragmentation to
introduced tree pathogens, each in themselves insuffi -
cient to cause the decline, had occurred sequentially,
resulting in eventual wholesale disappearance of the
species from a large part of its historical range.
LoGiudice (2006) ends with a plea to conservation scientists: ‘ We must train ourselves to look broadly (in the
ecological sense) and deeply (in the historical sense)
when investigating the causes of species declines. ’
Where long - term information is not available, this
does not mean that we are unable to act. While it is
useful to have the knowledge to make sensible predictions about which conservation interventions will be
successful, it is critical not to let action become delayed
by focusing exclusively on accumulating knowledge
about a particular problem or system. Recent developments in decision theory allow estimates about how a
system works to be updated as new information
becomes available, thus, over time, improving the likelihood of success of conservation action without
unnecessarily delaying action just because knowledge
is incomplete (for a review, see Grantham et al. , 2010 ).
This is particularly important where there are many
possible reasons for a particular observed decline or, as
in the case of the Allegheny woodrat, where a decline
is driven by many small effects acting in concert. A
detailed historical analysis of past declines can take
place alongside, and eventually guide, contemporary
conservation efforts.
7.2.1 Predicting f uture e cosystem
r esponses to c hanging c onditions
Despite the long history of human intervention, conservation theory and practice generally focus on how
present conditions, both natural and anthropogenic,
determine species ’ distributions and abundances. This
is consistent with the notion that conservation is a
crisis discipline in which we must act before knowing
all the facts (Soul é , 1985 ). For example, according to
the IUCN ’ s Red List, some 22 per cent of vertebrates are
threatened with imminent extinction (IUCN, 2008 ).
Action to enhance their chances of persistence is
urgent, although investment thus far has been limited
(Bottrill et al. , 2008 ).
Processes have generated and shaped the patterns
that we see as a fl eeting snapshot today, and processes
are the rules that govern how ecosystems will respond
to future changes. A fi rst key contribution of long - term
ecology to conservation, then, is that palaeoecological
and historical data can help unravel these rules; the
way that ecosystems and species responded to past
changes might tell us something about how they will
react in the future to management or threat.
In some cases, the story of a decline and, thus, the
conservation intervention required to reverse that
decline, is clear. For example, the ban on trade in ivory
of African elephants, introduced in 1989, successfully
led to recovery of the population, although there are
still hotspots of continuing trade and elephants are still
declining rapidly in some places (Stiles, 2004 ; Lemieux
& Clarke, 2009 ).
Sometimes, the cause of population declines is a
combination of natural variability and changing levels
of harvesting, such that the appropriate policy response
is much less certain. For example, more than ten
million tonnes of Peruvian anchovetta ( Engraulis
ringens ) were harvested in some years before the stock
collapsed in the early 1970s. The collapse was apparently brought about by a combination of the level of
exploitation and natural population variability in the
Peruvian upwelling system. The decline persisted into
the mid - 1980s, when the population began a period of
increase towards its earlier levels before collapsing
again during the late 1990s. Because the balance
between supply and demand effects remains uncertain,
policy decisions relating to this fi shery are diffi cult
(Pontecorvo, 2001 ). However, long - term data are critical in explaining fl uctuations in such fi sheries, and
history shows us that common species, such as the