MMENTAR Economies and L' terrorism f^ mFa\ Whenwhitefliesattacl< \WM?i LETTERS I BOOKS I POLICY FORUM I EDUCATION FORUM I PERSPECTIVES LETTERS edited by Jennifer Sills Switch to Corn Promotes Amazon Deforestation THE UNITED STATES IS THE WORLD'S LEADING PRODUCER OF SOY. HOWEVER, MANY U.S. FARMERS are shining from soy to corn (maize) in order to qualify for generous government subsidies intended to promote biofliel production (7); since 2006, U.S. corn production has risen 19% while soy production has fallen by 15% (2). This in turn is helping to drive a major increase in global soy prices (5), which have nearly doubled in the past 14 months. The rising price for soy has important consequences for Amazonian forests and savanna- woodlands (4). In Brazil, the world's second-leading soy producer, deforestation rates (J) and especially fire incidence (6) have increased sharply in recent months in the main soy- and beef- producing states in Amazonia (and not in states with little soy production). Although dry weather is a contributing factor, these increases are widely attributed to rising soy and beef prices (5, 7), and studies suggest a strong link between Amazonian deforestation and soy demand (8,9). Some Amazonian forests are directly cleared for soy farms (8). Farmers also pur- chase large expanses of cattle pasture for soy production, effectively pushing the ranchers farther into the Amazonian frontier or onto lands unsuitable for soy production (9). In addition, higher soy costs tend to raise global beef prices because soy-based livestock feeds become more expensive (70), creating an indi- rect incentive for forest conversion to pasture. Finally, the powerful Brazilian soy lobby is a key driving force behind initiatives to expand Amazonian highways and transportation net- works in order to transport soybeans to market, and this is greatly increasing access to forests for ranchers, loggers, and land speculators (77,12). In a globalized world, the impacts of local decisions about crop preferences can have far- reaching implications. As illustrated by an apparent "com connection" to Amazonian deforesta- tion, the environmental benefits of corn-based biofiiel might be considerably reduced when its fiill and indirect costs are considered. WILLIAM F. LAURANCE Smithsonian Tropical Research Institute, Apartado 0843-03092, Balboa, Anc?n, Panama. E-mail: laurancew@si.edu References and Notes 1. P. C. Westcott, "U.S. ethanol expansion driving changes throughout the agricultural sector" (www.ers.usda.gov/amberwaves/september07/features/ethanol.htm). 2. National Agricultural Statistics Service Acreage Report, U.S. Department of Agriculture (www.usda.gov/nass/PUBS/rODAYRPT/acrg0607.pdf). 3. USDA-ERS (www.ers.usda.gov/data/priceforecast/data/futmodsoybeans.xls). Growing global demands for soy for edible oil, livestock feed, and biodiesel are also contributing to high soy prices. 4. The corn-soy-deforestation link was evidently first noted by D. C. Nepstad et ai., The Amazon in a Changing Climate: Large- Scale Reductions of Carbon Emissions from Deforestation and Forest Impoverishment [Amazon Institute for Environmental Research (IPAM), 2006]. 5. C. Angelo, Desmatamento cresce 8% na Amazonia, Foiha de Sao Paulo Online (wwwl.folha.uol.com.br/ folha/ambiente/ultl0007u337678.shtm?. 6. ImazonGeo (http://imazongeo.org.br/alerta2.php). Deforestation. The aftermath of forest burning in central Amazonia. R. A. Butler, "Is the Amazon more valuable for carbon off- sets than cattle or soy?" (mongabay.com, 17 October 2007); http://news.mongabay.com/2007/1017- amazon.html. D. C. Morton et al., Proc. Nat. Acad. Sei. U.S.A. 103, 14637 (2006). D. C. Nepstad etal., Conserv. Biol. 20, 1595 (2006). D. L. Hard, in Protein Sources for the Animal Feed Industry (Animal and Production Health Proceedings, EAG, Rome, 2002), pp. 125-140. W. E Laurance etal., Science 291, 438 (2001). P M. Fearnside, Environ. Conserv. 28, 23 (2001). NASA Funding Slow, Not Steady, After Space Race AFTER READING D. KENNEDY'S EDITORIAL "Sputnik nostalgia" (5 October, p. 17), I find myself in a state I did not expect?one of dis- appointment. Kennedy writes about the posi- tive effects the launch of Sputnik had on edu- cation and the nation's educational commu- nity. These improvements resulted largely from an increase in federal sponsorship that came as part of the backlash from Sputnik. Yet, there lies within this seemingly fine out- come an issue that needs to be addressed. The National Aeronautics and Space Administration (NASA) was formed along with a dramatic increase in federal ?mding for science and science education in response to the former Soviet Union's incredible achieve- ment (7). When Neil Armstrong became the first person to set foot on the moon, the gov- ernment's interest in science dropped almost immediately. Because of the sudden lack of fiinding, the Apollo program was discontin- ued just 6 years after Apollo 11 landed in the Sea of Tranquility, in order to save fionds for the shuttle and Skylab programs (2). Lately, NASA has received additional funding to attempt a second series of missions to the moon as part of the Constellation Program (5), but the long-awaited increase is the bitter- sweet result of an imaginary space race (4). It seems that only when faced with the threat of looking stupid or coming in second place does our government open its wallet to science (7,4). MICHAEL]. GOLDSTEIN Department of Biology, Rutgers University, Camden, NJ 08102, USA. www.sciencemag.org SCIENCE VOL318 14 DECEMBER 2007 Published by AAAS 1721 I LETTERS References 1. J. F. Kennedy, Special Message to the Congress on Urgent National Needs, Washington, DC, 25 May 1961. 2. R. W. Orloff, Apoiio by the Numbers (NASA History Division, Washington, DC, 2000). 3. W. Gerstenmaier, paper presented before the Subcommittee on Space, Aeronautics, and Related Sciences, Washington, DC, 28 March 2007. 4. R. Block, "NASA points to foreign competition to spark support," Orlando Sentinel, 23 October 2007. Memory Suppression in PTSD Treatment? IN THEIR RESEARCH ARTICLE "PREFRONTAL regions orchestrate suppression of emotional memories via a two-phase process" (13 July, p. 215), B. E. Depue et al. suggest possible "implications for therapeutic approaches" for emotionally distressing memories. They speculate that the results "provide the possi- bility for approaches to controlling memories by suppressing sensory aspects of memory." As experimental psychopathologists, we ap- plaud the elegant experimental approach and welcome new ideas for clinical innovation. However, the proposal that suppression would be a beneficial strategy for clinical intrusive memories is directly counter to treatment outcome data. For example, the gold standard treatment for posttraumatic stress disorder (PTSD) is cognitive behavior therapy that involves repeatedly and inten- tionally bringing the trauma memory and associated affect to mind?a technique that is antithetical to suppression (7). Empirically supported theories of PTSD implicate cognitive avoidance (e.g., via thought suppression) in its persistence (2), with avoidance of trauma memories in the acute phase predicting PTSD at one year (3). While suppression may reduce distress in the short term, it predicts symptom mainte- nance (i.e., exacerbated trauma memories) in the long term. The tension between epidemiological and treatment data and the apparent implications of the Depue et al. observations are worthy of attention, and may provide a more sophisti- Letters to the Editor Letters (~300 words) discuss material published in Science in the previous 3 months or issues of general interest. They can be submitted through the Web (www.submit2science.org) or by regular mail (1200 New York Ave., NW, Washington, DC 20005, USA). Letters are not acknowledged upon receipt, nor are authors generally consulted before publication. Whether published in full or in part, letters are subject to editing for clarity and space. cated understanding of both areas. In the mean- time, there is a need for caution and for carefiil consideration of the relevant literature before inferring clinical implications from experimen- tal studies such as these, particularly when a suggestion is liable to harm patients. EMILY A. HOLMES/ MICHELLE L. MOULDS,^ DAVID KAVANAGH^ ^Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford 0X3 7JS, UK. ^School of Psychology, The University of New South Wales, Sydney, NSW 2052, Australia. 'School of Medicine, The University of Queensland, Herston, OLD 4029, Australia. References NICE, "Post-traumatic stress disorder (PTSD): The man- agement of PTSD in adults and children in primary and secondary care" Tech. Report No. CG026 (National Institute for Clinical Excellence, 2005). A. Ehlers, D. M. Clark, Behav. Res. Ther 38, 319 (2000). A. Ehlers, R. A. Mayou, B. Bryant, 7. Abnorm. Psychol. 107, 508 (1998). Response HOLMES ETAL. RAISE THE EXCELLENT POINT that suppression seems antithetical to the use of cognitive behavior therapy (CBT), espe- cially exposure therapy, for disorders like CORRECTIONS AND CLARIFICATIONS Reports: "DNAdouble-strand breaks trigger genome-wide sister-chromatid cohesion through Ecol (Ctf7)"by E. ?mletal. (13 July, p. 245). In the print and HTMLversions, the labels on the red and green shapes in Fig. 4 are missing. The corrected figure appears here. The labels appear in the PDF version. A no DSB Chrl Chrll cohesin -*- sister chromatids cohesion generation S cohesion generation inhibited G2/M cohesin loading around the DSB cohesion generation (DSB and genome-wide) G2/M TECHNICAL COMMENT ABSTRACTS COMMENT ON "Tumor Growth Need Not Be Driven by Rare Cancer Stem Cells" James A. Kennedy, Fr?d?ric Barab?, Armando G. Poeppl, Jean C. Y. Wang, John E. Dick Kelly et ai (Brevia, 20 July 2007, p. 337) questioned xenotransplant experiments supporting the cancer stem cell (CSC) hypothesis because they found a high frequency of leukemia-initiating cells (L-IC) in some transgenic mouse models. Hov?ever, the CSC hypothesis depends on prospective purification of cells v?ith tumor-initiating capacity, irrespective of frequency. Moreover, we found similar L-IC frequencies in genetically comparable leukemias using syngeneic or xeno- geneic models. Full text at iflrara/.sciencemag.org/cgi/content/fuH/318/5857/1722c RESPONSE TO COMMENT ON "Tumor Growth Need Not Be Driven by Rare Cancer Stem Cells" Jerry M. Adams, Priscilla N. Kelly, Aleksandar Dakic, Stephen L. Nutt, Andreas Strasser A critical issue for cancer biology and therapy is whether most tumor cells or only rare "cancer stem cells" sustain tumor growth. Although the latter model seems supported by the minute proportion of human leukemia cells that can grow in immunodeficient mice, evidence that more than 10% of cells in many mouse leukemias and lymphomas are transplantable challenges its generality. Full text at www.sciencemag.org/cgi/content/full/318/5857/1722d 1722 14 DECEMBER 2007 VOL 318 SCIENCE Published by AAAS www.sciencemag.org I LETTERS PTSD. In responding, we need to consider complexities in the treatment of these disor- ders that we could only briefly allude to in our Research Article (13 July, p. 215) (7). First, Holmes et al. note that PTSD patients who characteristically avoid their traumatic memories have a poorer prognosis. However, unsystematic avoidance by a patient is not the same as a systematic therapeutic process of directed suppression, which involves the acquisition of neural suppression over a number of trials. Second, we do not advocate suppression as a sole means of treat- ment for PTSD, but rather as a complemen- tary treatment with other methods. For exam- ple, it may be necessary to revisit an emotion- ally distressing memory before it can be con- trolled [our Research Article and (i)]. Currently, only about 30 to 70% of PTSD patients respond successfully to exposure therapy alone. Even these "responders" are only classified as such because they experi- ence reductions in just one or two key symp- toms (2). Other symptoms may still be vivid, and patients may suffer from relapses. Few long-term comprehensive studies of the relapse rate of PTSD symptoms have been reported beyond 6 months. Further- more, because PTSD research lacks rigorous randomized clinical trials, "responder" lev- els have been overreported (5). We believe, therefore, that conceptualization and testing of complementary therapeutic approaches is needed. Some forms of CBT may tap into the brain mechanisms underlying suppression. Research suggests that cognitive restructuring could benefit sufferers of PTSD (4). Cog- nitive restructuring processes may involve attaching a new emotional significance to a negative memory or cognition, as well as less- ening physiological arousal (J, 6). Further- more, new responses paired with an original conditioned stimulus may have inhibitory influences over the amygdala via a pathway from the medial prefrontal cortex to the baso- lateral amygdala to the central amygdala (7, S). In addition, research examining the cogni- tive manipulation of emotional significance, known as reappraisal, has shown increased activation in areas of the middle and inferior frontal gyri and decreased activation in the amygdala (9). These are the specific pre- frontal areas involved in suppression in our Research Article. Perhaps all of these findings explain why it may be necessary to revisit an emotionally distressing memory before it can be controlled via suppression. In any case, such processes may provide part of the biolog- ical basis for exposure and restructuring CBT methods. BRENDAN E. DEPUE/'2*TIM CURRAN/2.3 MARIE T.BANICHi^'^" ^Department of Psychology, University of Colorado, Boulder, CO 80309, USA. ^Center for Neuroscience, University of Colorado, Boulder, CO 80309, USA. ^institute of Cognitive Science, University of Colorado, Boulder, CO 80309, USA. "Department of Psychiatry, University of Denver Health Sciences, Denver, CO 80208, USA. *To whom correspondence should be addressed. E-mail: depue@colorado.edu References 1. B. E. Depue, T. Curran, M. T. Banich, Psychol. Sri. 17, 441 (2006). 2. R. Bradley et ai, Am. ]. Psychiatr. 162, 214 (2005). 3. G. Harvey, R. A. Bryant, N. Tarrier, Clin. Psychol. Rev. 23, 501(2003). 4. B. Nemeroff et ai, ]. Psychiatr. Res. 40,1 (2006). 5. J. Debiec, V. Doyere, K. Nader, J. E. Ledoux, Proc Nati Acad. Sei. U.S.A. 103, 3428 (2006). 6. I. Izquierdo, M. Cammarota, Science 304, 829 (2004). 7. G. ]. Quirk etal.,]. Neurosa. 23, 8800 (2003). 8. M. R. Milad, G. J. Quirk, Nature 420, 70 (2002). 9. N. Qchsneref o/.,;. Cognit. Neurosci. 14,1215 (2002). r'lfijii:^; You're Holding Sustainable Science The pages of this journal are made of recycled fiber. The staff of Science is doing its share to reduce, reuse, and recycle. The paper used in printing this journal contains reused materials. The addi- tional vi/ood used to create this paper comes from a paper mill participating in the PEFC Council (Programme for the Endorsement of Forest Certification) ? ensuring the paper is made from a sustainable managed forest. And in the future Science and AAAS will look to do more to advance science and conserve the environment. j?^y^ Sustainable Science, Now \^/-j Printed on Recycled Paper Science 1724 14 DECEMBER 2007 VOL 318 SCIENCE Published by AAAS www.sciencemag.org