different philosophical approaches toecosystem management, which includeshow different people value the aesthetic,spiritual and ethical aspects of biodiversity .These and other issues are complicated bypowerful economic and political intereststhat not only have high stakes associated withalternative policy outcomes, but also employscientific experts to support their positions.Despite vigorous differences of opinionbetween combatants, without exceptionthey share the belief that science is the appro-priate battleground, as well as the assump-tion that if a perception can be created thatscience is on your side, you will win. In theLomborg case, for example, Scientific Ameri-can’s editors subtitled the magazine’s collec-tion of responses “Science defends itselfagainst The Skeptical Environmentalist”, as ifthe authors are speaking ‘for’ science, ratherthan (as was actually the case) criticizingLomborg’s scientific claims and their signifi-cance for policy. It is this distinction,between science and policy advice, that thescientific community needs to address.Political decisions that involve differentinterest groups are inherently difficult tomake, because any adopted policy is boundto infringe on someone’s (overt or vested)interests. The process of achieving a legiti-mate outcome involves bargaining, negotia-tion and compromise — political manoeuv-ring that is well beyond the scope of science.‘Science’ is not a monolithic entity. In thewords of the chemist Henry Bauer, it is “amosaic of the beliefs of many little scientificgroups”. This diversity stems from the per-spectives of individual scientists them-selves, as well as from the nature of theobjects studied. In climate research, forexample, the scientific uncertainties are sogreat that it is impossible to exclude a widerange of future outcomes, ranging from rel-atively mild to globally catastrophic. Even ifscience could provide a crystal-ball view ofthe future, justification for any particularclimate policy would depend on more thanwhat science alone is capable of providing,including desirable societal and environ-mental outcomes .Some scientists believe that ‘science’alone provides a sufficient basis for deci-sion-making, in that a problem is identified,various hypotheses are tested, remedialpolicies suggested and implemented — thenthe situation improves. But putting the onusof problem resolution onto science bringsall the messy realities of politics into thepractice of science. Rather than making pol-itics more scientific, this approach, in fact,makes science more political. Indeed, I havenever come across any real-world policyissue involving science and decision-mak-ing that has resolved itself in this logical butoversimplistic manner.Why science has become politicalThe answer lies in an ‘iron triangle’ of mutu-ally reinforcing interests. In one corner is thepolitician loath to make a decision that willupset part of her constituency; she is conse-quently happy to pass the onus of resolutioncommentaryNATURE|VOL 416|28 MARCH 2002|www.nature.com 367Roger A. Pielke JrPublication of Bjorn Lomborg’s The SkepticalEnvironmentalist in September 2001 wasimmediately followed by an unprecedentedmobilization of environmental advocatesagainst the book, its author and publisher(see ‘From teapot to tempest’, below), thereverberations of which are still continuing.The Lomborg affair merits attention notbecause of its robust criticisms, characterassassination and pressure politics — theseare nothing new — but because its extreme-ness could mark a watershed in how sciencerelates to policy and politics. Whether BSE,ecosystem functioning, genetically modifiedorganisms (GMOs), cloning or vaccination,science is increasingly the battlefield onwhich political advocates, not to mentionlawyers and those with commercial interests,manipulate ‘facts’ to support their positions.It is urgent that the scientific communitychanges if it is to prevent science’s contribu-tion to effective policy development frombeing diminished, and the practice of sciencefrom being compromised.GridlockPoliticization of science has always been, andalways will be, integral to political advocacy.To take some examples:Global climate change has been the sub-ject of raging arguments for decades. Somepeople and organizations suggest that theproblem is minimal and will take care ofitself. Others advocate dramatic, immedi-ate changes to global energy policies. Yetothers believe that science cannot defini-tively predict climate change or economicfutures and that a more sensible politicalapproach would emphasize so-called ‘no-regrets’ adaptation and mitigation.Nuclear power has been a subject ofintense political debate and activism for evenlonger. Considerable scientific effort hasbeen devoted to assessing risks associatedwith nuclear plants and nuclear-waste stor-age, with advocates and opponents ofnuclear power each using ‘science’ to sup-port their positions. Many other issuesinvolving risk assessments (for example,GMOs and chemicals added to food andwater) share similar characteristics.Biodiversity is another controversy inwhich ecologists and the public are focusedon science. Most of the attention is directedon the relationship of biodiversity to eco-system functioning. How much diversity isdesirable, and for which species? The argu-ment is often less about science than aboutPolicy, politics and perspectiveThe scientific community must distinguish analysis from advocacy.From teapot to tempestThe Skeptical Environmentalistby statistician Bjorn Lomborg (Cambridge University Press, 2001) is a survey ofglobal environmental problems and issues. The nub of the controversy is Lomborg’s endorsement, from hisself-described ‘environmentalist’s’ perspective, of the work of the late Julian Simon, a renowned Copernicaneconomist espoused by the US right wing for his optimism about environmental issues such as populationgrowth. Lomborg’s conclusion is that, broadly, “things are getting better” in a range of environmental areas. To illustrate the points made in this Commentary, a criticism of Lomborg’s science can be found atwww.ucsusa.org/environment/mahlman.pdf, and a criticism of the significance of Lomborg’s argument is inThe Times Higher Education Supplement16 Nov. 2001, p 23.For a selection of other reviews and comments about the controversy see:Pimm, S. & Harvey, J. Nature414, 149 (2001), andCorrespondence by