The text that follows is a PREPRINT.
Please cite as:
Laurance, W.F., M.A. Cochrane, P.M. Fearnside, S. Bergen, P. Delamonica, S. D’Angelo, T. Fernandes, C. Barber. 2001. Author response to S. Schwartzman and R. Bonnie. Science dEbates. 31 May 2001. http://www.sciencemag.org/cgi/eletters/291/5503/438
Copyright: American Association for the Advancement of Science (AAAS)
The original publication is available at http://www.sciencemag.org
Debating the future of the Brazilian Amazon
We are pleased to respond to Schwartzman and
criticisms bear an uncanny similarity to those made earlier by members of the
competing IPAM team. In fact, most of
these criticisms fall apart on close inspection. Perhaps most
astonishing is Schwartzman and Bonnie ’s assert ion that the
2 is more conservative than ours(3) .we were that built
Like us, the IPAM group evaluated
historical deforestation along Amazonian highways and then extrapolated these
results into the future. However, the
IPAM effort was based on a
of only four highways that had caused especially heavy deforestation. We used a far more
reliable method, which involved assessing deforestation along all
Amazonian highways, including several that had caused only limited
deforestation. Our extrapolations
were therefore more
conservative and robust than those of IPAM.
Because of this important bias, the IPAM study actually projects a
greater increase in future deforestation rates (400,000-900,000 ha yr-1)
than does our study (269,000-506,000 ha
In addition, the IPAM study is far from comprehensive,
because it fails to account for the effects of infrastructure projects and
unpaved roads on Amazonian forests. Some
roads, such as the Northern Perimeter Road, will carve large swaths across the
Amazon, strongly influencing deforestation, logging, mining, and other
activities. Infrastructure projects such
as powerlines, gaslines, and hydroelectric reservoirs also contribute directly
to forest-degrading activities because they require road networks for
construction and maintenance.
of this can be seen in the Ecuadorian and Brazilian Amazon, where roads
associated with gas- and powerlines and reservoirs have led to dramatic rises
in slash-and-burn farming, logging, market hunting, and land speculation (4,
5). Our assumption that major
infrastructure projects will behave like unpaved roads—because they cannot be
constructed without first making roads—therefore is logical and defensible.
The IPAM study has other key limitations. It does not consider vast forested lands that
would be inundated by planned hydroelectric reservoirs in the Amazon. It also fails to consider the influence of
protected and semi-protected areas (such as national parks, national forests,
and indigenous reserves) on spatial patterns of forest loss and
degradation. Finally, it distinguishes
only between forested vs. deforested lands
fact that this is an obvious oversimplification. Many activities, such as selective logging,
forest fragmentation, surface fires, wildcat mining, and overhunting, can
degrade forest ecosystems without causing deforestation per se. Thus, the failure of the IPAM study to
predict the extent of forest degradation significantly reduces its
While most of Schwartzman and Bonnie’s assertions can be
easily rebutted, they do raise a valid point.
A debatable aspect of our models is the assumption that
river-channelization projects would likely lead to increased logging, deforestation,
and other degrading activities along rivers, comparable to those caused by
admittedly, educated guesswork, because no
such projects exist in the Amazon on which to base such extrapolations. While our remote-sensing analyses suggest
that forests near rivers with heavy boat traffic are especially prone to
deforestation (5), further studies are needed to predict the impacts of
river-channelization on Amazonian forests.
In summary, many of the large infrastructure projects included in our study—such as the Porto Velho-Urucu gasline, which will penetrate into the “pristine” heart of the Amazon—are likely to have dramatic impacts on the pattern and pace of forest conversion. While predictive models such as ours can always be improved, ignoring such projects in the name of waiting for better data would be to neglect one of the most important features of Avança Brasil. Our Policy Forum article helped to initiate a vigorous debate about the Avança Brasil program, and we regard this as a very healthy and timely development.
William F. Laurance1,2, Mark A. Cochrane3, Philip M. Fearnside4, Scott Bergen5, Patricia Delamonica2, Sammya D’Angelo2
1Smithsonian Tropical Research Institute, Apartado 2072, Balboa, Panamá
2Biological Dynamics of Forest Fragments Project, National Institute for Amazonian
Research (INPA), C.P. 478, Manaus, AM 69011-970, Brazil
3Basic Science and Remote Sensing Initiative, Michigan State University, East Lansing,
MI 48823, USA
4INPA Ecology Department, C.P. 478, Manaus, AM 69011-970, Brazil
5Department of Forest Science, Oregon State University, Corvallis, OR 97331, USA
1. D. C. Nepstad et al. Avança Brasil: Cenários Futuros para a Amazônia (Instituto de
Pesquisa Ambiental da Amazônia, Belém, Brazil, 2000).
2. G. Carvalho, A. C. Barros, P. Moutinho, and D. C. Nepstad, Nature 409, 131 (2001).
3. W. F. Laurance et al., Science 291, 438 (2001).
4. B. Holmes, New Scientist 151(2048), 43 (1996).
5. S. Bergen et al., The Future of the Brazilian Amazon: Development Trends and
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