Proceedings of the National Academy of Sciences USA
www.pnas.org December 11, 2007 vol. 104 no. 50 19697-19702
Climate change impacts on forestry
Andrei P. Kirilenko and Roger A. Sedjo
Edited by William Easterling, Pennsylvania State University,
University Park, PA, and accepted by the Editorial Board August 16,
2007 (received for review February 14, 2007)
From the abstract:
Changing temperature and precipitation pattern and increasing
concentrations of atmospheric CO2 are likely to drive significant
modifications in natural and modified forests. Our review is focused
on recent publications that discuss the changes in commercial
forestry, excluding the ecosystem functions of forests and nontimber
forest products. We concentrate on potential direct and indirect
impacts of climate change on forest industry…
Sample excerpt from text:
It is likely that changing temperature and precipitation patterns
will produce a strong direct impact on both natural and modified
forests. A number of biogeographical models demonstrate a poleward
shift of potential vegetation for the 2CO2 climate by 500 km or more
for boreal zones (11-13). The equilibrium models and some dynamic
vegetation models project that this vegetation shift toward newly
available areas with favorable climate conditions will eventually
result in forest expansion and replacement of up to 50% of current
tundra area. There is, however, a concern that the lagged forest
migration (compare the tree species migration rates after the last
glacial period of few kilometers per decade or less to projected
future climate zones shift rate of 50 km per decade) may lead to
massive loss of natural forests with increased deforestation at the
southern boundary of the boreal forests and a correspondent large
carbon pulse (13-15).
www.pnas.org December 11, 2007 vol. 104 no. 50 19697-19702
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“In 1991, a report said logging would have to be
reduced because changes in temperature and
rainfall in the South-West would lead to a drop
in productivity and a natural loss of trees.
“Dr Schultz said the report was never published
because the Government said that its climate
predictions were too severe and outdated. But the
estimates of a 20 per cent drop in rainfall and
temperature rises of 1C-2C in the next 50 years
were conservative compared with the latest
experiences and predictions.”
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http://www.thewest.com.au/printfriendly.aspx?ContentID=57016
Climate change forces cut to logging quota
4th February 2008, 6:00 WST
Logging of WA native forests will have to be
reduced in response to worsening climate change
but nothing is likely to happen for six years
because of a lack of scientific data,
Conservation Commission chairman John Bailey has
said.
Conservationists and scientists said it was not
acceptable that the research had not been done
and action was not under way because climate
change had been in mainstream planning and
management for at least 20 years.
Associate Professor Bailey said the impact of
climate change on sustainable logging rates would
be a focus of the mid-term review of the
2004-2013 Forest Management Plan due by the end
of the year.
While he believed changes would be needed, it was
not likely that enough solid information would be
available to alter the existing plan and changes
would instead be put in the next plan due in 2014.
It was not imperative that logging alterations
were made any earlier because the slow growth
rate of jarrah and karri meant climate impacts
would not be felt for 50-100 years. “I suspect
that there will be too many uncertainties and too
little need to act immediately but I suspect
there will be increasing need and an increasing
quality of science to be able to do that for the
next plan,” he said.
Conservation Council vice-president Beth Schultz
said logging rates had to be sustainable in
perpetuity and the climate change information
needed to ensure that should already be
available, given that government scientists had
warned that action was needed as early as 17
years ago.
In 1991, a report said logging would have to be
reduced because changes in temperature and
rainfall in the South-West would lead to a drop
in productivity and a natural loss of trees.
Dr Schultz said the report was never published
because the Government said that its climate
predictions were too severe and outdated. But the
estimates of a 20 per cent drop in rainfall and
temperature rises of 1C-2C in the next 50 years
were conservative compared with the latest
experiences and predictions.
University of WA school of earth and geographical
sciences researcher Ray Wills said to not have
the necessary science to make proper management
decisions in 2008 was “nothing less than
deplorable”. “A lot of our current distribution
of forest is determined by climate patterns that
reflect last century Š the climate this century
will be very different and as a consequence we
can’t afford delays on knowing what we’re doing,”
he said.
South-West scientist Peter Lane has lodged a
complaint with the Auditor-General about the way
climate change was considered when setting
current native timber logging rates.
A spokesman for the Department of Environment and
Conservation, which manages the forests, said a
lot of research into climate change and its
impact had been done and was continuing. Forest
plots were being monitored to measure change and
contribute to the next revision of the sustained
yields. Fire, dieback and the impact on
biodiversity also were being investigated.
SUELLEN JERRARD
http://www.thewest.com.au/printfriendly.aspx?ContentID=57016
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All About: Forests and carbon trading
By Rachel Oliver
For CNN
(CNN) — Cutting down trees is pretty much one of the worst things
you can do when it comes to climate change. Deforestation, by varying
accounts, contributes anywhere from 20 percent to 30 percent of all
carbon dioxide (C02) emissions — around 1.6 billion tons.
When you cut down trees you get a double whammy. First of all, they
are not called the lungs of the Earth for nothing — we clearly need
trees so that we and other animals can breathe. Trees also are in the
front line against pollution, breathing in millions of tons of
greenhouse gases a year that they store in their trunks.
According to the United Nations’ Environmental Programme (UNEP),
trees store a staggering 283 gigatons of carbon in their biomass.
When that is combined with the carbon found in the surrounding
deadwood and soil, the result is 50 percent more carbon than is
currently found in the atmosphere. When those trees are felled or
burned — trees that are comprised of 50 percent carbon — that
carbon is then released into the atmosphere.
According to the Council of Foreign Relations, the 2007 forest fires
in the United States — a relatively minor incident on a global scale
— contributed as much as 6 percent of North America’s total
greenhouse gas emissions that year.
But burning trees isn’t always a phenomena directly controlled by
humans. Many believe that global warming is exacerbating the rate of
naturally occurring forest fires around the world.
“Natural variation suggests the Amazon should have serious
drought-led fires at 400- to 700-year intervals, but today, they are
happening every five to 15 years,” the Independent recently reported.
“It’s a vicious cycle: cutting back the forests causes more global
warming, which then burns up more forests, which causes more global
warming, which burns up the forests even more, and on and on.”
There are currently around 10 billion acres of forest in the world,
covering 30 percent of the Earth’s land area. The world’s forest
cover is at least one-third less of the size it was before the
earliest days of agriculture.
Nations consider ‘carbon trading’
According to the U.N.’s Food and Agricultural Organisation (FAO),
around 32 million acres of forests disappear every year, most of it
in the tropics. The main reason for forest clearing hasn’t changed in
10,000 years. As much as 80 percent of all deforestation is done
because of the need to clear land for agriculture. The WWF is now
warning that if nothing is done 60 percent of the Amazon rain forest
could disappear by 2030.
A recent UK study on the environment, the Stern Report, reached the
conclusion that many others are coming to: If the world wants to curb
emissions cheaply and quickly then it has to simply stop cutting down
so many trees.
One way to do this is to make it more economically viable for the
countries hosting these rain forests to preserve them.
Carbon trading was introduced as part of the Kyoto Protocol’s goal to
reduce certain industrial nations’ greenhouse gas emissions to below
1990 levels by 2012. The idea was that countries whose emissions fall
under the emissions cap — the permitted level of carbon dioxide
equivalent emissions per year — could then sell those carbon credits
to countries who are not able to meet their own caps.
The caps are supposed to fall over time with the price of the carbon
credits, therefore rising due to scarcity levels. Proponents of
carbon trading envisage a new global investment market based on
emissions trading, where companies and countries have incentives to
invest in developing world projects due to the highly coveted carbon
credits they receive for doing so.
With regard to forests, the idea is basically they should be worth
more than they are. And countries (generally poor ones) who have the
rain forests should be compensated for protecting them, particularly
when they are under so much economic pressure to open them up to
mining companies. Indonesia and Brazil now find themselves in the top
four of the world’s top polluting nations as a result (around 80
percent of Brazil’s greenhouse gas emissions tally comes from
deforestation).
The economic argument goes that you make it more financially
appealing to countries not to allow their forests to be cut down.
“It’s insanity that a single service company, Google, has a market
value of $200 billion, while all the services of all of the world’s
great forests are valued at nothing,” Hylton Murray-Philipson, head
of Rainforest Concern, recently told the Independent newspaper.
On a per ton of carbon basis, countries such as Indonesia can earn
between $1 and $5 to destroy the trees, according to a recent article
in the Guardian — or they can earn around $30 (the market price of
carbon credits in Europe at the time the article was written) for
protecting them. Equally, a 2006 study on deforestation by the
British government said that without action on this issue, each ton
emitted could cause $85 of damage to the global economy.
Can interests of both rich, poor be served?
The real concern, however, is that carbon trading only really serves
rich nations; the issue being that carbon trading could put the vital
resources of the developing world in the hands of nations that can
use carbon credits as a way to counter, or delay, reductions of their
own greenhouse gas emissions at the same time.
At the U.N. climate change conference held last December in Bali,
Indonesia, the World Bank launched its Forest Carbon Partnership
Facility (FCPF), a fund financed by the UK, Germany, the Netherlands,
Australia, Japan, France, Switzerland, Denmark and Finland (with The
Nature Conservancy also chipping in).
The $160 million fund, the World Bank says, will be used to “support
programs targeting the drivers of deforestation and develop concrete
activities to reach out to poor people who depend on forests to
improve their livelihoods. It will also help developing countries
build the technical, regulatory, and sustainable forestry capacity to
reduce emissions from deforestation and degradation.”
There has already been some confusion over the exact role the World
Bank is trying to play in all of this. The World Bank says it wants
to reduce global deforestation by 10 percent by 2010. But its critics
claim the World Bank has traditionally been a proponent of
deforestation.
There has also been concern over the impact of the forest carbon
trading scheme on local forest communities that earn a living from
the forests.
In the Democratic Republic of Congo (DRC) the World Bank is facing
opposition from Pygmy groups and local communities which rely on the
Congo basin, the world’s second-largest virgin rain forest, for their
livelihoods, following a leaked report on the Bank’s activities
there. The report came from the Bank’s own inspection panel, and it
accused the Bank of encouraging commercial logging practices “based
on exaggerated estimates of the export revenue to be reaped,” while
discouraging sustainable forestry and conservation at the same time,
reports the Inter Press Service.
The report has also found that the financial benefits of logging have
gone to foreign firms, not local ones. The Pygmy groups and others
are asking for these industrial logging practices to stop immediately
and are asking for more assessments of the environmental impact of
logging. (Logging was actually banned in DRC back in 2002; since then
more than 100 new logging contracts have been issued).
Environmental groups have responded to the World Bank’s FCPF with
extreme caution. A joint statement signed by more than 80
environmental organizations around the world in response to the the
program queried its intentions, accusing the Bank of continuing “to
undermine its own climate change mitigation efforts by persisting in
funding fossil fuel industries on a global scale and enabling
deforestation.”
They have also sounded their alarm about why the program has been
pushed through too quickly with little consultation with affected
communities.
Sources: Stabroeck News; Inter Press Service; Green Left Weekly; IHT;
U.N. Food and Agricultural Organisation; Guardian; The Ecologist; The
World Bank; UN Environment Programme; Forest People’s Programme;
Friends of the Earth
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“This overview illustrates the potential for
widespread and rapid forest dieback,
and associated ecosystem effects, due to anticipated global climate change.”
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MASSIVE FOREST DIEBACK
Paper presented at Mountain Climate Sciences
Symposium : “Anticipating Challenges to Western
Mountain Ecosystems and Resources,” North Tahoe
Conference Center, Kings Beach, Lake Tahoe,
California – May 25-27, 2004
By Allen, Craig D.
U.S. Geological Survey, Jemez Mountains Field Station, Los Alamos, NM 87544
In coming decades, climate changes are expected
to produce large shifts in vegetation
distributions, largely due to mortality.
However, most field studies and model-based
assessments of vegetation responses to climate
have focused on changes associated with natality
and growth, which are inherently slow processes
for woody plants-even though the most rapid
changes in vegetation are caused by mortality
rather than natality. This talk reviews the
sensitivity of western montane forests to massive
dieback, including drought-induced tree mortality
and related insect outbreaks. This overview
illustrates the potential for widespread and
rapid forest dieback, and associated ecosystem
effects, due to anticipated global climate change.
Climate is a key determinant of vegetation
patterns at landscape and regional spatial
scales. Precipitation variability, including
recurrent drought conditions, has typified the
climate of the Mountain West for at least
thousands of years (Sheppard et al. 2002).
Dendrochronological studies and historical
reports show that past droughts have caused
extensive vegetation mortality across this
region, e.g., as documented in the American
Southwest for severe droughts in the 1580s, 1890s
to early 1900s, 1950s, and the current drought
since 1996 (Swetnam and Betancourt 1998, Allen
and Breshears 1998 and in press). Drought stress
is documented to lead to dieback in many woody
plant species in the West, including spruce
(Picea spp.), fir (Abies spp.), Douglas-fir
(Pseudotsuga menziesii.), pines (Pinus spp.),
junipers (Juniperus spp.), oaks (Quercus spp.),
mesquite (Prosopis spp.), manzanitas
(Arctostaphylos spp.), and paloverdes (Cercidium
spp.).
Drought-induced tree mortality exhibits a variety
of nonlinear ecological dynamics. Tree mortality
occurs when drought conditions cause threshold
levels of plant water stress to be exceeded,
which can result in tree death by loss of
within-stem hydraulic conductivity (Allen and
Breshears – in press). Also, herbivorous insect
populations can rapidly build up to outbreak
levels in response to increased food availability
from drought-weakened host trees, such as the
various bark beetle species (e.g. Dendroctonus,
Ips, and Scolytus spp.) that attack forest trees
(Furniss and Carolin 1977). As bark beetle
populations build up they become increasingly
successful in killing drought-weakened trees
through mass attacks (Figure 1), with positive
feedbacks for further explosive growth in beetle
numbers which can result in nonlinear ecological
interactions and complex spatial dynamics (cf.
Logan and Powell 2001, Bjornstad et al. 2002).
Bark beetles also selectively kill larger and
low-vigor trees, truncating the size and age
distributions of host species (Swetnam and
Betancourt 1998).
The temporal and spatial patterns of
drought-induced tree mortality also reflect
non-linear dynamics. Through time mortality is
usually at lower background levels, punctuated by
large pulses of high tree death when threshold
drought conditions are exceeded (Swetnam and
Betancourt 1998, Allen and Breshears – in press).
The spatial pattern of drought-induced dieback
often reveals preferential mortality along the
drier, lower fringes of tree species
distributions in western mountain ranges. For
example, the 1950s drought caused a rapid,
drought-induced ecotone shift on the east flank
of the Jemez Mountains in northern New Mexico,
USA (Allen and Breshears 1998). A time sequence
of aerial photographs shows that the ecotone
between semiarid ponderosa pine forest and
piñon-juniper woodland shifted upslope
extensively (2 km or more) and rapidly (< 5
years) due to the death of most ponderosa pine
across the lower fringes of that forest type
(Figure 1). This vegetation shift has been
persistent since the 1950s, as little ponderosa
pine reestablishment has occurred in the ecotone
shift zone.
Severe droughts also markedly reduce the
productivity and cover of herbaceous plants like
grasses. Such reductions in ground cover can
trigger nonlinear increases in erosion rates once
bare soil cover exceeds critical threshold values
(Davenport et al. 1998, Wilcox et al. 2003). For
example, in concert with historic land use
practices (livestock grazing and fire
suppression), the 1950s drought apparently
initiated persistent increases in soil erosion in
piñon-juniper woodland sites in the eastern Jemez
Mountains that require management intervention to
reverse (Sydoriak et al. 2000). Thus, a short-
duration climatic event apparently brought about
persistent changes in multiple ecosystem
properties. Over the past decade, many portions
of the Western US have been subject to
significant drought, with associated increases in
tree mortality evident. GIS compilations of US
Forest Service aerial surveys of insect-related
forest dieback since 1997 show widespread
mortality in many areas. For example the
cumulative effect of multi-year drought since
1996 in the Southwest has resulted in the
emergence of extensive bark beetle outbreaks and
tree mortality across the region. In the Four
Corners area piñon (Pinus edulis) has been
particularly hard hit since 2002, with mortality
exceeding 90% of mature individuals across broad
areas (Figure 1), shifting stand compositions
strongly toward juniper dominance. Across the
montane forests of the West substantial dieback
has been recently observed in many tree species,
including Engelmann spruce (Picea engelmanni),
Douglas-fir, lodgepole pine (Pinus contorta),
ponderosa pine, piñon, junipers, and even aspen
(Populus tremuloides).
A number of major scientific uncertainties are
associated with forest dieback phenomena.
Quantitative knowledge of the thresholds of
mortality for various tree species is a key
knowledge gap – we basically don’t know how much
climatic stress forests can withstand before
massive dieback kicks in. Thus the scientific
community currently cannot accurately model
forest dieback in response to projected climate
changes, nor assess associated ecological and
societal effects. More research is needed to
determine if warm minimum temperatures over the
past decade+ are exacerbating the effects of
droughts and insects on tree mortality, as: 1)
warmer temperatures result in greater plant water
stress for a given amount of water availability;
and 2) relaxation of low temperature constraints
on insect population distributions and generation
times may be allowing more extensive and rapid
buildup of outbreak population levels. It is
thought that substantial and widespread increases
in tree densities in many forests and woodlands
as a result of more than 100 years of fire
suppression also contributes to current patterns
of mortality, due to competitive increases in
tree water stress and susceptibility to beetle
attacks; however, more research is needed on the
effectiveness of mechanical thinning and
presecribed burning
as protective management approaches.
Substantial uncertainties exist about the
relationship between massive forest dieback and
fire behavior. Although severe (crown) fire
activity has apparently increased in some
overdense forest types in the West, in some areas
forest dieback is reducing the vertical and
horizontal continuity of a key crown fire fuel
component (live needles in tree crowns) as
needles drop from dead tress, and that reductions
in the spatial extent of uncontrollable crown
fires may result. Feedbacks between forest
dieback and fire activity (ignition
probabilities, rate of spread, severity,
controllability) need more work.
Recent examples of massive forest dieback
illustrate that even relatively brief climatic
events (e.g., droughts) associated with natural
climate variability can have profound and
persistent ecosystem effects. The
unprecedentedly rapid climate changes expected in
coming decades could produce rapid and extensive
contractions in the geographic distributions of
long-lived woody species in association with
changes in patterns of disturbance (fire, insect
outbreaks, soil erosion) (IPCC 2001, Allen and
Breshears 1998). Because regional droughts of
even greater magnitude and longer duration than
the 1950s drought are expected as global warming
progresses (Easterling et al. 2001, IPCC 2001),
the scale of forest dieback associated with
global climate change (Figure 3) could become
even greater than what has been observed in
recent years (National Research Council 2001).
Since mortality-induced vegetation shifts take
place more rapidly than do natality-induced
shifts associated with plant establishment and
migration
(Allen and Breshears – in review), dieback could
easily outpace new forest growth for a period of
years to decades in many areas. Further, as
woody vegetation contains the bulk of the world’s
terrestrial carbon, an improved understanding of
mortality-induced responses of woody vegetation
to climate is essential for addressing some key
environmental and policy implications of climate
variability and global change (Breshears and
Allen 2002). Thus it is important to more
accurately incorporate climate-induced vegetation
mortality and the complexity of associated
ecosystem responses (e.g., insect outbreaks,
fires, soil erosion, and changes in carbon pools)
into models that predict vegetation dynamics.
References Cited
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Drought-induced shift of a forest/woodland
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Drought, tree mortality, and landscape change in
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