308
D .L. Spittlehouse
final step involves a monitoring program to determine if changes are
taking place, and when the thresholds for concern and intervention have
been reached . This will also aid in refining the response plan.
Management responses will be a mix of adaptation, mitigation, and
protection measures . Prescriptions must be flexible and safe-fail, that is,
they do not compromise the health of the forest if the climate does not
change as predicted (Pollard , 1991). Responses will depend on whether
we are dealing with managed or unmanaged ecosystems. Even where we
are managing, it is likely that management will not be directed toward
most organisms in the ecosystem. Assessment will improve our ability to
select areas to target limited resources (Sandenburg, Taylor , & Hoffman,
1987; Woodman, 1987).
Adaptation is a response appropriate to managed ecosystems. An
example is changing the ecotypes or species planted after disturbance
(fire, harvesting) under a changed climate. The human adaptation response
would be changing our expectations of, and demands on, the forest
resource, for example , accepting a reduction in tree growth. Leaving
migration corridors and reserve areas would be an example of mitigation.
This may be the only way to address unmanaged ecosystems and wildlife
within a managed landscape. Protection would involve responses to
enhanced threats where current forests are still sustainable, such as,
improving integrated pest management and fire portection programs.
Many responses could fit under more than one definition, depending on
how, when, or where they are applied. For example, development of
drought tolerant stock would mitigate timber losses by adapting the trees
to the new climate.
Species and ecosystem processes have different sensitivities to climate.
Consequently, responses to climate change need to be at the species level
(Leverenz & Lev, 1987; Clark , 1991; Smith, Shugart , Bonan, & Smith,
1992; Pastor & Post, 1993). Species responses will result from an interplay
of competition, dispersal, and climatic factors (Malanson, 1993). Established trees tolerate large interannual variations in weather conditions
(Reifsnyder, 1989), and future rapid, large-scale devastation of plant
communities is unlikely. Populations of plants and animals at the edge of
their ranges are likely to be the most sensitive to climate change and may
act as early warning systems. Animal populations may move more rapidly
than plant populations in response to a change, though this requires that
appropriate habitats are available in other areas. Fragmentation of
habitat wili.make it diffcult for even resilient populations to move.
Response may be easier with managed rather than unmanaged ecosystems,
since intervention is part of management (Woodman, 1987; Peters , 1990;
Graham, Twiner, & Dale, 1990; Pollard , 1991; Wall, 1992). Any change
is usually assumed to be negative. However, in some situations there will
be an improvement over existing conditions. For example, warmer
temperatures may result in increased productivity of the vegetation in
D .L. Spittlehouse
final step involves a monitoring program to determine if changes are
taking place, and when the thresholds for concern and intervention have
been reached . This will also aid in refining the response plan.
Management responses will be a mix of adaptation, mitigation, and
protection measures . Prescriptions must be flexible and safe-fail, that is,
they do not compromise the health of the forest if the climate does not
change as predicted (Pollard , 1991). Responses will depend on whether
we are dealing with managed or unmanaged ecosystems. Even where we
are managing, it is likely that management will not be directed toward
most organisms in the ecosystem. Assessment will improve our ability to
select areas to target limited resources (Sandenburg, Taylor , & Hoffman,
1987; Woodman, 1987).
Adaptation is a response appropriate to managed ecosystems. An
example is changing the ecotypes or species planted after disturbance
(fire, harvesting) under a changed climate. The human adaptation response
would be changing our expectations of, and demands on, the forest
resource, for example , accepting a reduction in tree growth. Leaving
migration corridors and reserve areas would be an example of mitigation.
This may be the only way to address unmanaged ecosystems and wildlife
within a managed landscape. Protection would involve responses to
enhanced threats where current forests are still sustainable, such as,
improving integrated pest management and fire portection programs.
Many responses could fit under more than one definition, depending on
how, when, or where they are applied. For example, development of
drought tolerant stock would mitigate timber losses by adapting the trees
to the new climate.
Species and ecosystem processes have different sensitivities to climate.
Consequently, responses to climate change need to be at the species level
(Leverenz & Lev, 1987; Clark , 1991; Smith, Shugart , Bonan, & Smith,
1992; Pastor & Post, 1993). Species responses will result from an interplay
of competition, dispersal, and climatic factors (Malanson, 1993). Established trees tolerate large interannual variations in weather conditions
(Reifsnyder, 1989), and future rapid, large-scale devastation of plant
communities is unlikely. Populations of plants and animals at the edge of
their ranges are likely to be the most sensitive to climate change and may
act as early warning systems. Animal populations may move more rapidly
than plant populations in response to a change, though this requires that
appropriate habitats are available in other areas. Fragmentation of
habitat wili.make it diffcult for even resilient populations to move.
Response may be easier with managed rather than unmanaged ecosystems,
since intervention is part of management (Woodman, 1987; Peters , 1990;
Graham, Twiner, & Dale, 1990; Pollard , 1991; Wall, 1992). Any change
is usually assumed to be negative. However, in some situations there will
be an improvement over existing conditions. For example, warmer
temperatures may result in increased productivity of the vegetation in