Climate change futures: health, ecological and economic dimensions

HEALTH AND ECOLOGICAL
IMPLICATIONS
Outbreaks of the spruce bark beetle have caused
extensive damage and mortality from Alaska to
Arizona and in every forest with substantial spruce
stands (Holsten et al. 2000). The dead stands provide
superabundant kindling for lightning or human-induced
wildfires and are particularly vulnerable during
drought. Wildfires are hazardous for wildlife, property
and people, and they place demands on public health
and response systems. While some fires are natural
and can have positive effects on vegetation and insect
buildup, extensive, cataclysmic-scale wildfires pose
immediate threats to firefighters and homeowners, and
particles and chemicals from blazes and wind-carried
hazes cause heart and lung disease. Some fire byproducts
(primarily from buildings) are carcinogenic.
Hampshire. It is moving north with each warm winter.
Those trees in Boston’s historic Arboretum, designed by
Frederick Law Olmstead, have been drastically culled
to try to control the infestation.
Eastern Hemlock conifers play unique ecological roles.
Hemlocks colonize poor soils and scramble to the crests
of mountains. Their arbors are umbrellas for resting deer
in winter and the pine needles they shed nourish fish in
the deep forest streams they line. When stands of
Hemlocks die, their needles add large amounts of nitrogen
to the streams and tributaries, and the impacts of
their loss is under intense study (Orwig and Foster
2000; Snyder et al. 2002; Ross et al. 2003).
Figure 2.23 Hemlock Wooly Adelgid
66 | NATURAL AND MANAGED SYSTEMS
CASE STUDIES
Losing forests to fire also threatens the ecological services
they provide: a sink for carbon dioxide, a source of
oxygen, catchments (“sponges”) for flood waters, stabilizers
of soils, habitat for wildlife and, via extensive
watersheds, clean water. As sources of evaporanspiration
(evaporation, and transpiration through leaves) and
cloud formation, forests are integral to local climate
regimes and to the global climate system. The resilience
of large areas of boreal spruce forests that have succumbed
to beetle infestations, with resulting large-scale
diebacks and fire, are not well understood.
Figure 2.22 Spruce Trees
Dead stands of spruce trees infested with bark beetles.
Image: Natural Resources Canada, Canadian Forest Service
Hemlock Wooly Adelgid
Wooly adelgid poses a risk to New England forests
today. This aphid-like bug has already infected Eastern
Hemlock trees in Connecticut, Rhode Island and,
Massachusetts, and has moved into southern New
Image: Dr. Mark McClure, CT Agricultural Experiment Station
ECONOMIC DIMENSIONS
According to the US Department of Agriculture Forest
Service (Holsten et al. 2000), more than 2.3 million
acres of spruce forests were infested in Alaska from
1993 to 2000 and the infestation killed an estimated
30 million trees per year at the peak of the outbreak.
The Kenai Peninsula in Alaska, Anchorage’s playground,
is a devastated forest zone. In Utah, the
spruce beetle has infested more than 122,000 acres
and killed over 3,000,000 spruce trees. The losses
have amounted to 333 million to 500 million board
feet of spruce saw timber annually. Similar losses have
been recorded in Montana, Idaho and Arizona, with
estimates of over three billion board feet lost in Alaska,
and the same in British Columbia.
In British Columbia, nearly 22 million acres of Lodge
pole pine have become infested — enough timber to
build 3.3 million homes or supply the entire US housing
market for two years (The Economist 9 Aug 2003).
In the summer and fall of 2003 the wildfires cost more
than US $3 billion (Flam 2004). The loss of tree cover