Flagships, Umbrellas, and Keystones: Is Single-Species Management Passe in the Landscape Era?
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1 BiOlOgi , ( Vol 83. No 3. pp. 247 25 . 1998 I 1997 Published bs Llsevier Science Ltd Al) rights reserved Printed in Cireat Britain SOO 0 6-3 2 07(4 7)0 0081-5 0006-32117 98 $19.181 « (Jill L SI \ IF I< FLAGSHIPS, UMBRELLAS, AND KEYSTONES: IS SINGLE-SPECIES MANAGEMENT PASSE IN THE LANDSCAPE ERA? Daniel Simberloff Department of Biological Science, Florida State University. Tallahassee. Florida 323filb. Abstract needed. Thus, SOIIIC See CCOS.I'Venl Man- agement Because it is so difficult to monitor and manage every as a Trojan horse that would allow continued environmental name of tinnier,' resource aspect of biodiversity, several shortcuts have been pro- destruction in the management. posed whereby we monitor and. or protect single species. The recognition that sothe ecosystem% ho re keysione The indiewor species concept is problematic because there .species whose activities gi wern the well-being id many ii no consensus on what the indicator is supposed to indi- species suggests an appniach that min unite cate and because a is difficult to know which is the best other the best ecosystem management. V indicator species even when ice agree on what it should features of single-species and that indicate. The umbrella species ( a species that needs such we can iilentily keystone species and the inechanisinN came them to how v1(11 Ividc-lallgMg ic e 11 .01/h/ large tracts of habitat that saving it will automatically . 1111pOCIA , save many other species, seems like a better approach. ahnOS/ certainly derive information on tile lunclioning of although men WhCaler 1711111y other species will reallyfall the entire ecosystem that would be foetid in its manage- appro- under the umbrelhi is a matter of faith rather than ment. Some keystone species themselves may be priate targets for management, even when researc 'h. intensive management of an. indicator or an hut, they are not, umbrella specie) tor eNample, by transplant or supple- our understanding of the ecosystem will be .greatly , non - mental feeding is a contradiction in terms because the increased. Keystone species Mar 1101 he a panacea, (Ter. knoll him l est of the community 10 be miliewed or protected does WC 1101 •I'CI many ecosystems have keystone .species, and the that lead to their not receive such treatment. .4 flagship .s pecies.1101111011.1* evreriment. identification are often very , ditirallUllie large vertebrate. is one lhal can be used to difficult. I /99\ .Pubbsbed - : anchor a conservation campaign because it arouses public by Ilsevier Science Ltd. rights reset I ea interest and .sympathy. but a flap/lip need not be a good indicator or umbrella. And consermtion flagship spe- Keywords: adilptiVC 111:111 42011C111.. CCOS stem hea It h. i ie.% is often very expensive. Further, management regimes ecosystem management, endangered species. flagship of t wo ,flagship species can conflict. Ecosystem manage- species. indicator species. keystone species, landscape ment. open on a landscape scale. is a proposed solution ecology. umbrella species. - to Prublems of.vbigle species management. Keep the Ce0- SySICI11 healthy. according this view. and component species will all thrive. 1 lowever, cwiservationisis have concerns about ecosystem management. First, it IS var- INTRODUCTION iously Mined, and many definitions emphasife the com- modities ecosystems provide for humans rather than how In an era of burgeoning conservation needs and humans can protect ecosystem.s. Second. the term 'eco- tightening budgets. an increasingly loud claim is that the system health ' is ill-delmed and associated with an out- scope of conservation management must be expanded . moded, superorganismic vieW (!i the ecosystem. Third. to achieve economies of scale and efficiency. According it us istem Managelnelll seems focused on processes and so to this view, managing populations of particular species would appear to permit losses ofspecies so long as they of interest will lead us to fall further and further behind ( /id not greatly allect processes like nutrient-cycling. in meeting the challenge of preserving biodiversity. as Fourth, ecosystem management is °Pen implemented by more and more species fall below a threshold of adaptive management. This may make it difficult to study imperilment and funding in no way keeps pace with the underlying mechanisms driving an ecosystem and to their individual needs. The only way to deal with this know when an entirely new management approach is challenge is then seen to be to manage at least entire ecosystems. if not whole landscapes. b■ unified !'resent address: 1)epartnient oF Ecolouv & methods designed to save all their inhabitants at one - I:volution:try . t..itiversitv of I ennessee. K u t viIIc. TN 1799(,. t time. 248 D. Siniberlolf However. the precise objectives of such methods have Criteria for choosing such indicator species are very not often been articulated beyond vague aims to 'pre- controversial ( Landres al., 1988). at least partly serve the environment' or to 'maintain biodiversity'. and because of confusion over what the indicator should it is not always clear exactly how management of such indicate. Generally, we want an indicator to indicate the high-level entities as ecosystems will supersede manage- 'health' of the system, but different persons view differ- ment of their component species. This paper attempts to ent things as constituting health. For example. whether understand the specific goals of management at the species richness alone. independently of species' identi- ecosystem level and higher. and also to compare pro- ties. contributes to the functional health of a community posed procedures to those of traditional management or ecosystem is hotly debated and currently under focused on individual populations and species. intensive study ( Baskin. 1994: Tilman and Downing. The examples used to elucidate these matters will be 1994). For some persons. species richness itself eco- primarily North American. largely because of the system health - the tacit goal of all conservation should author's familiarity with conservation on that continent. be species richness, and. ipso hiu.to, a rich community is A large fraction of the discussion relates to management a healthy one. For still others, structural diversity and actions aimed at satisfying the Endangered Species Act aspects of cunclion (like nutrient c■cles) are the sine qua (1973) of the United States. This legislation has become non of health. independently of species richness or the major vehicle for protecting biodiversity in the Uni- composition. The reductio alkairdum of this confu- ted States (Mann and Plummer. 1995). It is reactive. sion of goals is the proposition (Noss. 1990) that we rather than proactive, and explicitly targets species and should monitor irtuall■ everything as indicators • a populations, in that it specifically provides protection large group of species. dominance-diversity curves. for species (and. in certain instances, some populations canopy height dkersny. percent co' er. nutrient cycling rather than entire species) that are already felt to be and predation rates. etc. The problem is that this full set doomed to extinction if new action is not taken to of indicators lea% es nothing to he indicated. as opposed redress their decline. However, often the Act has been to measured directl■. Of course the absence of resources invoked to save entire ecosystems because, under some to do all this measurement was the raison d'jtre for circumstances, it provides for protection of the habitat indicator species in the first place! of an endangered species, and that habitat includes the Even if we concede at the outset that all we want the biotic as well as the abiotic habitat. Thus, a recent indicator species to indicate is the presence and popula- interpretation by the Supreme Court says that the Act tion trends of a group of other species in a communit■ can prevent habitat destruction (Baker. 1995) if such of interest, it is not so obvious how to choose the best destruction 'harms' endangered species or populations. species for this purpose. At the ■er least, we would The Endangered Species Act also mandates that, in need a pilot study measuring co-occurrence patterns addition to calling a halt to most activities causing the and correlations of population fluctuations, plus ease of decline of an endangered species. a management plan monitoring. for all species in the group. To my knowl- must be produced that will rehabilitate the species by edge. such a pilot study has never been attempted. The bringing its population size above the threshold of scale of observation would also he important for an endangerment. These management plans have become indicator ( Mee and Carroll. 1994: Weaver. 1995). the testing ground for various ideas on how and at what Species like the large vertebrates discussed below might . level to conserve nature in the United States. be excellent indicators for other species that require massive, continuous tracts of habitat, but they may not Indicator, umbrella, and flagship species be good indicators of species such as insects that might Because monitoring and managing all aspects of biodi- do very well in a landscape fragmented into small pat- versity that might interest us (including species richness ches, so long as the habitat of the patches was appro- and composition. physical structure, and processes) are priate. so difficult, a variety of shortcuts have been proposed Finite de inieux. often vertebrate species are chosen as whereby attention is focused on one or a few species. indicators simply because they are so charismatic that a The most venerable of these approaches is that of the manager feels obliged to monitor them anyway and indicator species. Managers use indicators for two dif- nourishes the vague hope that such a 'flagship species' ferent reasons—first because their presence and fluctua- (see below) will fortuitously reflect the health of the tions are believed (or hoped) to reflect those of other entire system.