15. Effects of Climate Change on Forest Ecosystems
307
for meeting public demands for food and services and economic development rank well ahead of concern for distant, unknown climates (Watson ,
Bach, & Goklany, 1992). However, technologies are a buffer only as long
as energy supplies last and climate fluctuations are small (Baker, Ruschy ,
& Skaggs, 1993). Even if human society is somewhat insulated from
change, forest ecosystems are not. Forest managers need to assess
how the ecosystems may change and develop management responses
(Sandenburgh, Taylor, & Hoffman , 1987; Pollard, 1991). Management
has to take place at a much smaller scale than the resolution of the
current global climate models. Most assessments have been at the regional
scale, and many of these analyses used inappropriate models (Clark,
1991; Malanson, 1993; Pastor, & Post, 1993). I will present a framework
and examples for assessing forest sensitivity to climate change and
developing response for managed forests at the site level. I make no
assumptions about which, if any, of the global climate model scenarios is
possible. The methodology could also aid managing forests for current
climatic variability.
Framework for Responding to the Threat of Climate Change
Like Waterstone (1993) , I believe that it is unlikely that international
action will be sufficient to halt the equivalent doubling of the atmospheric
carbon dioxide concentration. Forestry may be required to playa role in
reducing the rate of increase, though the size of the gain is debatable
(Pollard, 1991; Dixon , Brown , Houghton et al. , 1994). I will concentrate
on the need to maintain forest ecosystems healthy enough to tolerate
climate changes, as recommended in Wall (1992). We need to consider
all parts of the ecosy stem , not ju st the species important for timber.
Furthermore, forestry operations depend on the weather (e.g. , warm
winters can restrict winter logging) . Responses can be determined from
existing data, expressed in terms of the sensitivity of ecosystems to
climate/weather variability. We must recognize that any climate change
may not be gradual, and the rate of change will probably be more
important than changes in the mean (Schneider, 1990; Pollard, 1991;
Clark, 1991).
Development of a response plan requires a framework for the analysis.
First there must be the identification of the issue of concern and the
degree of change in the resource that would be considered a serious
problem. Second is -the development of scenarios, that is, determination
of the sensitivity of ecosystems to changes in climate variables, and how
this compares with potential future climate changes. The third step is the
development of management responses. This includes activities to be
taken at the time changes occur as well as activities needed now to
facilitate future response. Benefit/cost analysis should be done here. The
307
for meeting public demands for food and services and economic development rank well ahead of concern for distant, unknown climates (Watson ,
Bach, & Goklany, 1992). However, technologies are a buffer only as long
as energy supplies last and climate fluctuations are small (Baker, Ruschy ,
& Skaggs, 1993). Even if human society is somewhat insulated from
change, forest ecosystems are not. Forest managers need to assess
how the ecosystems may change and develop management responses
(Sandenburgh, Taylor, & Hoffman , 1987; Pollard, 1991). Management
has to take place at a much smaller scale than the resolution of the
current global climate models. Most assessments have been at the regional
scale, and many of these analyses used inappropriate models (Clark,
1991; Malanson, 1993; Pastor, & Post, 1993). I will present a framework
and examples for assessing forest sensitivity to climate change and
developing response for managed forests at the site level. I make no
assumptions about which, if any, of the global climate model scenarios is
possible. The methodology could also aid managing forests for current
climatic variability.
Framework for Responding to the Threat of Climate Change
Like Waterstone (1993) , I believe that it is unlikely that international
action will be sufficient to halt the equivalent doubling of the atmospheric
carbon dioxide concentration. Forestry may be required to playa role in
reducing the rate of increase, though the size of the gain is debatable
(Pollard, 1991; Dixon , Brown , Houghton et al. , 1994). I will concentrate
on the need to maintain forest ecosystems healthy enough to tolerate
climate changes, as recommended in Wall (1992). We need to consider
all parts of the ecosy stem , not ju st the species important for timber.
Furthermore, forestry operations depend on the weather (e.g. , warm
winters can restrict winter logging) . Responses can be determined from
existing data, expressed in terms of the sensitivity of ecosystems to
climate/weather variability. We must recognize that any climate change
may not be gradual, and the rate of change will probably be more
important than changes in the mean (Schneider, 1990; Pollard, 1991;
Clark, 1991).
Development of a response plan requires a framework for the analysis.
First there must be the identification of the issue of concern and the
degree of change in the resource that would be considered a serious
problem. Second is -the development of scenarios, that is, determination
of the sensitivity of ecosystems to changes in climate variables, and how
this compares with potential future climate changes. The third step is the
development of management responses. This includes activities to be
taken at the time changes occur as well as activities needed now to
facilitate future response. Benefit/cost analysis should be done here. The