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4 P E E R R E V I E W E D •> INTEGRATING BIOLOGICAL DIVERSITY AND RESOURCE MANAGEMENT An essential approach toproductive, sustainable ecosystems By JohnR. Probst and Thomas R. Crow Call for Papers The JOURNAL OF FORESTRY is extendinga call for papersin the followingareasof biodiversity. All papers will be peer-reviewed priorto publicationin the JOURNALOFFORESTRY and mayor may not be printedwith otherarticles in the series. Papers are solicited on ecosystemapproaches to biodiversity,old-growthecological processes, biodiversity and ecosystem function,population viability,diverse monitoring strategiesfor diverseobjectives, endangered and threatened species, tropical rainforests,managingfor biodiversityon nationalforests,timber-cuttingpatternsto optimize biodiversity,evaluationof a)ternatives in intensely managed forests, and examples of successfulbiodiversity management in managedforestsand humandominatedlandscapes. Submit proposals or completedpapersto N. TaylorGregg, Editor, JOURNALOF FORESTRY, 5400 Grosvenor Lane, Be- thesda, MD 20814-2198 (301) 897-8720. Completed papers shouldfollowthe guidelinesfor generalscientificpapers as presented in "Guidelines for Con- tributors,"May 1990 JOURNAL OF FORESTRY, p. 43--44. 12 JOURNALOF FORESTRY t isnotuncommon today forforesters to findthemselves at the center of controversy.A skeptical public often criticizes forest management activities, especiallytimber harvesting and road building, and often perceivesmanagementas detrimental to many organismsthat dependon the forest for their survival. While the for- ester might argue that an intensively managedforest is likely to be a healthy forest, others call for "natural forests" in which ecologicalprocessesare allowed to occur without interference from chain saws and skidders. Againstthis background,the issueof conserving biological diversity is receiving increasedattention in professionaljournals, the popularmedia, and Congress.Growingconcernsare being expressedaboutforest destructionand habitat losses throughout the world, and aboutthe acceleratinglossof species due to the cumulative impact of human activities. While the spotlight currently focusesonrelatively few species-the spotted owl, the red-cockadedwoodpecker,the black-lootedfer- ceptof biologicaldiversityservesas a broad framework for consideringmany of today'simportantresourceissues. The fact that the total number of specieson Earth, even to an order of magnitude,is unknownmakesit difficultto know what is being lost. Current estimates of the number of plant and ani- mal speciesworldwide range from 5 and 50 million,but fewer than 2 million specieshave beendescribedand catalogued(Wilson1985,May 1988).Most of this diversityis inconspicuous. Probably only 1-2% of Earth's speciesare higher plants and less than 0.2% are vertebrates; the remainder are a vast array of invertebrates, algae, fungi, andothermicroorganisms that, despite being inconspicuous, provide valuable ecological services.Althoughit is difficult to quantifyexact rates of species lossthroughouthistory,scientistsgenerally agree that current extinction rates far exceed the rates documented in geologicrecords. But what does this have to do with forestry?Forests, especiallypublicforests, are increasinglyviewed as valuable reserves in which large tracts can be managedto protectbiologicaldiversity. NationalForest ManagementAct regulations already specify that the USDA Forest Service must consider biologicaldiversity in the planningproret--a more comprehensive discussion cess, and must monitor and evaluate is developingthat dealswith biological the effectsof implementingany forest diversity and its importanceto ecosys- plan on biologicaldiversity. Furthertem health and productivity.The con- more, concernsabout the lossof biologJohn R. Probst is research ecologistand ThomasR. Crow is project leader, USDA Forest Service, North Central Forest ExperimentStation,Rhinelander,WI. icaldiversityhaveresultedin draft legislation to make conservation of biological diversity a national goal Foresters shouldplay a role in these policydiscussions as well as find practical solutions to the problem. This role, however, will be determined largely by how we perceivethe issues throughregionalto global.When discussingbiologicaldiversity,it is impor- and understand the conceptsrelating to biologicaldiversity. It is alsoimportantto view biological diversityas somethingmorethan local "species richness." Management to maximizespeciesrichnessat the local level often favors "generalist" organismsat the expenseof "habitat specialists."In the process,speciescould be lost from large areas or whole regions.Land managersneed to be especially concernedabout plant and animalspeciesthat are habitat specialists, and about specieswith low population densities, that require large homeranges,with poor dispersaland colonizingabilities,or that are proneto What Is It? The first questionalwaysis: Can you g•ve me a good definitionof biological diversity? Probably the most widely cited definition comes from Technolo- gtes to Maintain Biological Diversity (Office of Technology Assessment 1987): "Biological diversity refers to the variety and variability among livIng organismsand the ecologicalcomplexesin which they occur"(p. 5). No matter how well stated, technical definitions rarely make good operatlonal definitions. From a practical viewpoint,it is usefulto considerthree elements of diversity--genetic, species, and ecosystem.Each is related. For example, it is important in conservingany speciesto maintaincritical ecosystems(or habitats) and retain as much genetic diversity as possible. Each element can operate at a variety of scalesin time and space. The time scale can vary from a few hours (the life spanof a microorganism) to decades (viability assessments) or even millenma (evolution).Biologicaldiversity occurs at all spatial scales, from local tant to considerappropriateelements and scales. local extinction. In contrast, common species,habitat generalists,or species able to colonize disturbed habitats are morelikely to prosperundera variety of landusepatterns(fig. 1, p. 14). SpatialConsiderations Dividing large and continuoustracts Key No. o• Described Taxon Species 1 Monera (Bacteria, Blue-green Algae) 2 Fungi 3 Algae 4 Plantae (MulticellularPlants) 5 Protozoa 4,760 46,983 26,900 248,428 30,800 6 Porifera(Sponges) 7 Coelentarata(Jellyfish,Corals, Comb Jellies) 8 Platyhelminthes (Flatworms) 9 Nematoda(Roundworms) 10 Annelida(Earthwormsetc.) 11 Mollusca(Mollusks) 12 Echinodermata(Stadish etc.) 13 Insecta 5,000 9,000 12,2OO 12,0OO 12,O00 50,000 6,100 751,0oo 14 Non-insect Arthropoda (Mites, 15 16 17 18 19 Spiders,Crustaceansetc.) Pisces(Fish) Amphibia(Amphibians) Reptilia(Reptiles) Aves(Birds) Mammalia(Mammals) 123,161 19,056 4,184 6,300 9,040 4,000 Source E O Wdson Ed 1988 B•od•ve•sttyNal Acad Sc• Press Washington of natural habitat into smaller habitats surrounded by altered or disturbed areas--called habitat fragmentation-is a majorconcernrelatingto biological diversity (Harris 1984, Wileove 1987). The problemsof extinctionand colonizationon habitat fragmentsare similar to the patterns biogeographershave S•zeofindividual organisms represents numberofdescribed species in majortaxon.UnitArea:[] = 1,000described species. FEBRUARYI•I 13 suchas animalsrequiringinterior forest conditions(e.g., neotropicalmigratory birds) or those requiring several habitatsin closeproximityat different times of the year or at different stages of development(e.g., amphibianswith both terrestrial and aquaticlife forms) Somearea-sensitive speciesmayalso be "edge-sensitive"when biotic factors (predators, browsers, nest parasites, competitors)or abioticfactors(changes in microclimate)decreasetheir reproductivesuccess.Edge-sensitivespecies includemany birds as well as reptiles, amphibians,and plants. The significanceof habitatcontrastalongan edge depends on the species. Ubiquitous roadsand forest openingsdramatically increaseedge environments. Figure 1. Generalistsare foundin a variety of ecosystems. In contrast,habitat specialists are limited to only a few ecosystems,such as old-growth forestsand native grasslands. Maintaining regional diversity dependson maintaining ecosystemsthat are rare and endangered. Someopen-landspeciesare edgesensitiverelative to forest edges.Prairie grouse, for example, suffer increased predation near forest edges Grassland birds such as bobolinks and been recordingfor more than a century on oceanic islands, so habitat fragments are often called habitat islands. They may be patches of old-growth surroundedby second-growthforests, prairie fragments embeddedin a matrix of agriculturallands, or oncefreeflowing rivers fragmented by hydroelectric and water diversionprojects. In all cases, what were continuous areas are now separatedby less suitable, and in some cases inhospitable, habitatsfor manyspecies. Although natural disturbance is a commonoccurrence,habitat fragmentation is aggravated in human-domi- nated landscapes.Declines in migratory bird populations in the eastern deciduous forest are related to forest fragmentation (Robbins 1979, Whitcomb et al. 1981). Extensive fragmentation due to dams and impoundments hascontributedto the endangeredstatus of fish in the Colorado River (Oho et al. 1983). Human activities not only result in the destruction of habitats, but speciesdependingonthe remaining habitat fragments often become iso- latedfrom otherpopulations depending on when and how the habitat is frag- several sparrow species also have lowerproductivitynearedges(Johnson and Temple 1990). Other area-sensitivespeciesmay be more accuratelydescribedas humansensitive. These include many large mammals, especially carnivores (timber wolf, grizzlybear, blackbear, Florida panther)that characteristically exist in low densities and are wide- ranging.The problemhere hasmoreto do with the fact that human contact is often fatal for the animals. For exam- ple, black bears prefer habitat that includesboth forestsand openingswith a high degreeof edge and a variety of plant communities;but large, relatively uninhabitedtracts of such land havedisappeared in manyareas,bringing bears into closer contact with hu- mans.It is not surprisingthat the principal source of mortality for the panther, Key deer, and manatee (all endangered) and for the threatened black bear in Florida is collisions with motor vehicles(Harris 1989). Maintaining large wide-rangingmammalsin the eastern United States may require linking several undevelopedareas together with landscapecorridors. mented. When small populationsof a species are widely scattered, the chancesof local extinctionare greater and the chances of recolonization de- crease. Habitat fragmentation can adversely affect "area-sensitive"species, 14 JOURNALOF FORESTRY From Speciesto Ecosystems A fundamentalproblemfor biological diversity is defininglong-termviability for species.It is more complex than simplythe minimumpopulationneeded to survive long-term, random population fluctuations.To assesspopulation dynamics accurately, resource managersmustconsiderreproductiverate, populationor habitat age structure,recruitmentrate, survivorship,and ability to disperse. They must also take into accountthe amountand quality of critical habitat and how it is distrib- uted. Many suboptimalhabitats may temporarily support higher than expected populationsdue to emigration from more productive sources (i.e., sourceand sink relations), so populations do not always respondimmediately to landscapealterations. The effects of habitat lossare rarely linear; instead, populationsoften decline sharply once a threshold is reached. This is particularly true for speciesthat are locally or temporarily successful andemigrateto lesssuitable habitats,where they reproducebelow replacement levels. Adding or eliminatinga few high-qualitybreedinghabitats can causea regional populationto change substantially. For example, populations of the endangered Kirtland's warbler remained remarkably stablefor the past 2 decadesexceptfor 20% declinesin 1974and 1987, when a few large breedingareasbecameovermature at the sametime (Probst 1988), and a 20%increasein 1990after a large block became suitable habitat (J. Probst, unpublisheddata). Speciesthat are reasonablycommon, or even abundant, can rapidly disappear if their reproductionor habitat is altered. Vast flocks of passengerpigeonsoncefilled the skies,but hunting ulations (i.e., ecologicallyfunctional, Connor 1988) using a landscape and ecosystemapproach. Managers are devising practical monitoring systems that are biologically, statistically, and technically sound. One approach uses indicator species:by monitoringthe population of a few species,managersattempt to interpret population trends of many species. However, monitoring plans are almost never comprehensive enough,and debate continueson what constitutesan indicatorspeciesand on how muchindicatorspeciescanrepresent the ecologicalrequirements and population trends of other species (Landres et al. 1988). Strategies are being developed to monitor species groups(Verner 1984)and specificmanagement problems (snag densities, area-sensitivespecies,dispersal corridors, amphibianbreedingareas, etc.). However, inventory should be completedbeforemonitoringplansare developed, and general biodiversity assessment is a higher priority than monitoring. Preserving single species(especially vertebrates) has dominated the atten- tion of conservationists, but preserving ecosystems is receivingmore attention (Noss 1983). Regional ecosystem approaches are needed for preserving plants, invertebrates, and less visible vertebrates. Restoring prairies and oak savannahs in the Midwest and longleafpinecommunitiesin the South, maintainingold-growth forests in the Northwest, savingmoistand dry tropical forests and wetlands throughout duringcriticalnestingperiodsreduced the world all reflect this concern. Such their reproductivesuccessand contributed to their extinctionover a 20-year period.The Eskimocurlew, onceoneof communitiesare important elementsof regional and global diversity. A comprehensiveapproachto conservingand enhancingbiologicaldiversity requires taking into accountboth speciesand the most abundant shorebirds in North America, alsodisappearedquickly. Managersshouldfocuson landscape and ecosystemfeaturesthat affectpopulation size and distribution ecosystems. in the United States (Hoekstra et al. 1979).Comprehensivestudiesto determine minimum viable populationswill be possiblefor only a few selectedspecies. A practicalalternative is managing for large and well-distributedpop- should play a role in these policy discussions as well as Public Benefits from find practical Biodiversity solutions rather than attempting the complicatedtask of determiningwhat constitutes"minimumviable"populations. An estimated 2,400 to 2,600 vertebrates alone occur Foresters Many benefitsof biologicaldiversity are widely acknowledged.Some plant and animalspeciesare vital for human utilization as food, fiber, or medicinal drugs. Hunting, fishing, and esthetic appreciationof animalsandplantsgive pleasureto peopleand add billionsof dollarsto economieseach year. Plants to theproblem FEBRUARY1991 15 and animals are used in genetic re- search for selective breeding and as sourcesof new genetic material. The need to preserve genetic diversity is particularly critical given predicted geographicshifts in speciesdistribution dueto climaticwarming. The number of major commercialspeciesin agriculture and forestry are limited, so becausethey often managelarge, contiguoustracts of land. Suchtracts can mitigatethe effectsof habitatfragmentation in surroundinglandscapes.For example, large blocks of forestland may provide the interior forest conditions neededfor breedingpopulations of area-sensitivebirds; these populationsmay, in turn, expandto lesssuit- Thechallenge ofconserving biological diversity istoocomprehensive . . . to bemet onpubliclandsalone III EllIll IIII1[111 IIII new plant varieties may have to be developed using traditional breeding methodsas well as biotechnology. Scientistsare becomingincreasingly aware that biotic diversity is essential to healthyand productiveecosystems. Diverse flora and fauna facilitate de- composition, nutrient cycling, and other ecologicalprocesses.Animals both large and smallaffect forest compositionand regenerationthroughherbivory, seed dispersal,and population regulationof other organismsthrough a multiplicityof interactions.Biodiversity provides alternative food chains, biologicalpest controls,and increased silviculturaloptions.For example,genetic diversity has a very important relationship to site productivity, and someof the most valuablegenetic complexes may have already been lost (Ledig 1988, Monserud and Rehfeldt 1990). Diverse life forms vary in their tolerance to environmentalstress, so communitycompositioncan be a sensitive environmental monitor of climatic changeor pollution.Many noncommercial speciesare valuableas site indicators for forestry and agriculture.Much of the diversity responsiblefor ecosystem health and sustainabilityis "invisible diversity"that is out of sight and thus out of mind. ManagementResponsibilities Public and industrial managersare nnportant to the conservation effort 16 JOURNALOFFORESTRY pendonactivehumaninvolvement.Active management, not just passive protectionism,is neededto coordinate different land ownership objectives Active managementmust create landscapesthat facilitate movement and dispersal of large mammals. Active managementis neededto restore speciesthat are extirpated due to direct or indirect human impact and to reduce the threat of exoticson native species Active planning will ensure that oldgrowth forests,with their uniqueproperties, are representedthroughoutthe regional landscape,adding to regional diversity.Active managementcansupplementin situ conservationof genetic diversity by collecting and storing seedsand pollen of endangeredplant species.Active managementis vital to providing critical habitats when and where they are neededto ensure that uncommon species do not become threatenedor endangered. able habitats on adjacentlands. However, not even the largest national forest or national park is ecologically Recommendations isolated from activities and conditions Preserving biologicaldiversity is a in surroundingareas. complex problem that encompasses a The challenge of conserving biologi- variety of scientific, social, and ecocal diversityis too comprehensive and nomic considerations.Piecemeal apinclusive to be met on public lands proacheswill likely.result in oversimalone. Nor is it realistic to think that conservingbiologicaldiversity is nothing more than establishingparks and preserves. Only a small fraction of Earth's surface will ever be under the protective status of a national park, a nature preserve, or a wildlife sanctuary, and the least protectionis likely where it is neededthe most--the tropics of Asia, SouthAmerica, and Africa. We cannot remove people and resourceuse from the systemand create pristine forests, nor can we somehow return to presettlement conditions. Therefore, conserving and enhancing biologicaldiversity must becomean integral part of natural-resourcemanagement on the 95% of the landscape that sustainsa wide variety of human activitiesand resourceuses,including timberharvestingandfoodproduction. At regional,national,andglobalscales, major efforts to maintain biologicaldiversity must occur outsideparks and preserves--on lands having a variety of usesand ownerships. It is ironic that as humans alter the ecosystems onwhichthey depend,conserving diversity will increasinglyde- plification, frustration, and new, unanticipatedproblems.There are no "five easy steps" or simple solutions. Nevertheless, applying some general recommendationscan help maintain and enhancebiologicaldiversity. ß Use a regional perspectivewhen considering biologicaldiversity. ß Think beyond the boundaries of specificownershipswhen planningand managing. ß Plan and manageover large areas rather than usinga stand-by-stand approach. Consider the cumulative impact of individualprojectson regional populationsand resources. ß Emphasize multispeciesand ecosystemmanagementinsteadof singlespeciesand tree management.Simply stated:becomean ecosystemmanager ß Provide habitat sufficient to main- tain species of concern (e.g., large wide-rangingmammals), not just sufficient habitat to attract immigrants from more productivesources. ß Maintain or create spatialpatterns (largepatches,landscapelinkages,low contrast between adjacent patches) that enhanceconditionsfor problem species.For example,alter cutting patterns and harvest schedules to reduce forest fragmentation. ß Includethe full spectrumof ecological assemblages within the landscape, from early successional to old-growth communities.Provide a variety of sites for eachforesttype and age as a coarse filter for genetic and ecosystem d•versity. ß Conductecologicalsurveysandinventories. Know what is on the land, where it is, and how much is there. ß Monitor problemspeciesand problem ecosystems.Wherever possible, supplement monitoring of indicator specieswith guild (groupsof speciesoccupyingsimilarniches)monitoringand d•rect ecosystemmonitoring. Relate changesto localtreatments. Interpret local changes relative to broader regaonalchanges. ß Become better follows awareness! informed. Action Maintainingandenhancingbiological diversity touches all aspects of resourcemanagement.An obviousreason for protectingbiologicaldiversity lSto ensuresustainableproductivityof forest resourcesfor presentand future generations. It is part of being good stewards.From a broaderperspective, biologicaldiversity is an integral part of our cultural and esthetic appreciation of life. 36:1-9. Noss, R.F. 1983.A regionallandscape approach to maintain diversity. BioScience33:700-6. OFFICE OF TECHNOLOGY ASSESSMENT. 1987. Technologiesto maintain biologicaldiversity. Summary. U.S. Gov. Print. Off., Washington, ß Literature netic and environmentalcomponentsof variation of site indexin inlandDouglas-fir.For. Sci. Cited CONNOR,R.N. 1988. Wildlife populations: minimally viable or ecologicallyfunctional?Wildl. Soc. Bull. 16:80-84. HARRIS,L.D. 1984.The fragmentedforest. Univ. ChicagoPress, Chicago,IL. 211 p. HARRIS, L.D. 1989. The faunal significanceof fragmentationof southeasternbottomlandforests. P. 126-34 in The forested wetlands of the southernUnitedStates,D.D. HookandR. Lea, eds.USDA For. Serv. Gen. Tech. Rep. SE-50. HOEKSTRA, T.W., et al. 1979. Preliminaryevaluation of a national wildlife and fish data base. Trans. North Am. Wildl. & Nat. Resour. Conf. 44:380-91. JOHNSON,R.G., and S.A. TEMPLE. 1990. Nest predationandbroodparasitismoftallgrassprairie birds.J. Wildl. Manage.54:106-11. LANDRES,P.B., J. VERNER,and J.W. THOMAS. 1988. Ecological uses of vertebrate indicator species:a critique. Conserv.Biol. 2:316-28. LEDIG,F.T. 1988.The conservation of diversityin forest trees. BioScience 38:471-79. MAY, R.M. 1988.How manyspeciesare there on earth? Science 241:1441-49. MONSERUD,R.A., and G.E. REH•'ELDT.1990. DC. Stock #052-003-01058-5. ONO, R.D., J.D. WILLIAMS, and A. WAGNER. 1983.Vanishingfishesof North America. Stone Wall Press, Washington,DC. PROBST,J.R. 1988. Kirtland's warbler breeding biologyand habitat management.P. 28-35 in Integratingforestmanagement for wildlifeand fish,T.W. HoekstraandJ. Capp,comps.USDA For. Serv. Gen.Tech. Rep. NC-122. ROBBINS, C. 1979.Effect of forestfragmentation onbird populations.P. 198-212in Management of north central and northeastern forests for nongamebirds, R.M. DeGraaf, ed. USDA For. Serv. Gen. Tech. Rep. NC-51. V•RNER, J. 1984. The guild conceptappliedto managementof bird populations.Environ. Manage. 8:1-14. WHITCOMB,R.F., et al. 1981. Effects of forest fragmentationon avifauna of the eastern deciduousforest. P. 125-205 in Forest island dynamicsin man-dominatedlandscapes,B. Burgessand D. Sharpe,eds. Springer-VerlagNew York, Inc., New York, NY. WILCOVE,D.S. 1987.From fragmentationto extinction. Nat. Areas J. 7:23-29. WILSON,E.O. 1985.The biologicaldiversitycrisis. BioScience 35:700-6. FEBRUARY1991 17