1. Matt Highnam
9/17/14
EBIO3190-001
Prof. Julia Hicks
Dale, V.H., L.A. Joyce, S. McNulty, .P. Neilson, M.P. Ayres, M.D. Flannigan, P.J. Hanson, L.C.
Irland, A.E. Lugo, C.J. Peterson, D. Simberloff, F.J. Swanson, B.J. Stocks and B.M. Wotton.
2001. Climate Change and Forest Disturbances. BioScience 51:723-734.
Critique #1
The effect of climate change on forests has been a hot topic for many studies in the
scientific community. However, the disturbances in forests that are caused by climate change
have been ignored, resulting in there being little to no data to refer to on the matter. This has
made it hard to endorse notions that climate change does significantly affect forest disturbances.
New modeling studies indicate that climate change has an important influence on vital aspects of
disturbances such as timing, frequency, duration, extent, and intensity. Disturbances shape forest
systems by playing a role in their composition, structure, and functional processes. Each
disturbance varies in their impacts on forests but they all potentially pose serious social,
economic, and ecological consequences. Thus, the importance of fully understanding,
anticipating, and preventing or controlling these disturbances cannot be understated. The goal of
this study is to demonstrate the direct influence that climate change has on forest disturbances
and how negatively forests will be affected in the future if the proper measures are not taken. The
study will focus on the U.S., whose main disturbances are fire, drought, introduced species and
pathogen outbreaks, hurricanes, windstorms, ice storms, and landslides, but it reflects what
occurs globally.

2. To examine and predict future climates, new general circulation models (GCMs) were
used to create scenarios. The scenarios generated spanned from 1895 to 2100 and involved
simulating atmospheric dynamics under a gradual increase in greenhouse gas concentrations.
These scenarios allowed the dynamics of forest ecosystems and communities under increasing
climate change over time to be examined in relation to forest-process and biogeography models.
One of the models was ran with large increases in temperature and moderate increases in
precipitation as to where the other model was ran with moderate increases in temperature and
large increases in precipitation. This provided contrast between the two models so that the
various aspects of climate change could be demonstrated.
The results from both models predicted that fire intensity overall would increase and that
the area burned could increase by as much as fifty percent. Drought was indicated to occur
within the next couple of decades in large parts if the U.S. but these areas were shown to
experience a drastic increase in precipitation as well. Insect and pathogen outbreaks were
predicted to exponentially increase because warming would result in the diversity of insects at
higher latitudes and since insects migrate at a faster rate than trees, new insects would be
introduced to some tree species. Introduced species were also predicted to increase because
temperature, drought, and cloud cover changes would shift the distributions of species.
Hurricanes and tornadoes were both predicted to become more and more frequent as well as
severe over time due to global warming. Lastly, ice storms and landslides were both predicted to
become more frequent over time but at varying locations depending on the changing climatic
conditions in certain areas. Overall, all of these disturbances were predicted to become more
frequent, more severe, and more variable in occurrence and location. The potential effects of all
of these exacerbated disturbances on forests in the U.S. were primarily predicted to be all

3. negative as they would cause loss of vegetation (mature especially), disrupt functional processes
(food webs, etc.), limit carbon amounts in soils, and decrease overall species diversity.
Many of the disturbances are cascading, which in the eyes of this study, makes all of the
predictions determined to be considered to be even worse. If climate change increases the
magnitude of these disturbances, which will all appear to result in largely negative effects on the
forests, then the forests of the U.S. will be in grave danger of dying and this will have a direct
effect on the social and economic aspects of human lives as well. This leads to the ultimate
conclusion of the study that more research needs to be done on predicting these potential
disturbance increases and on what measures or strategies can be used to prepare for them.
Overall, this study was very unconventional as it did not pull data from previous studies
because there were none, but rather it used models to predict future data and occurrences that
could be observed in studies. Although these models are very advanced technologically, the
actual real empirical and observed data just does not exist. This is no fault of the authors, but it is
a vital component of a valid conclusion. The authors themselves constantly used words such as
“probably”, “likely”, and “may” when discussing the effects the climate would cause. These are
words of doubt, not words of firm assertion that you expect from a study with a valid conclusion
that the authors are confident in. In the end, the authors did assert that they were using the
information available in combination with their own unbiased, professional knowledge of the
subject and that much more information via more studies was needed. However, they made
concise, reasonable, logical, and very knowledgeable, sound arguments to go along with their
models. Given all of these facets of the study, the conclusion cannot be accepted due to lack of
hard evidence but it can be considered valid due to the compelling, well-informed arguments
coupled with the advanced and unbiased models created.