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The federal government owns more than 264 millionhectares (ha) across theUnited States, representing nearly

one-third (29%) of the nation’s land area, and one-fifth(21%) just in the lower 48 states. These lands span a widearray of ecosystems, from frozen tundra in the north to sub-tropical hardwood hammocks in southern Florida. In turn,these habitats support diverse assemblages of native wildlife,includingmany that are rare or have suffered serious declines.Such rare or declining species are of particular scientificand conservation interest because of their heightened risk ofextinction.The Endangered SpeciesAct (ESA) of 1973 represents a for-

mal expression of the American people’s concern about theloss of plant and animal species to extinction.The federal gov-ernment has dual responsibilities under this act. Adminis-tration and enforcement of the act’s provisions are federalobligations of the US Fish and Wildlife Service (USFWS)within theDepartment of the Interior, and theNationalMa-rine Fisheries Service (NMFS) within the Department ofCommerce.A second area of responsibility relates to the fed-eral government’s role as the nation’s largest landowner andmanager, with broad responsibilities for managing the re-sources under its control. The mandates of federal agenciesvarywidely; consequently, land-management objectives rangefroma focus on protection andpreservation, as is the casewiththeNational Park Service (NPS), tomultiple uses of the land,

including resource extraction, as with the USDA ForestService and the Bureau of Land Management (BLM).Despite these differences in objectives, all federal land-

management agencies are obligated to comply with federalenvironmental laws and regulations such as the ESA. Thus,while considerable attention in recent years has rightfullyfocused on how to better protect endangered and threat-ened species on private lands, federal lands must play a keyrole in any national strategy for preserving the nation’s richarray of wildlife species. Protection of threatened or endan-gered plant species under the ESA, for example, differs de-pending on whether the plant is found on federal propertyor on private property. The no-take provisions under theact, which prohibit landowners from causing harm to listedspecies, apply only to animals. Plant species on private landsare, in general, protected onlywhere a federal action (e.g., reg-ulatory permit) is involved. In contrast, listed plants occur-ring on federal lands receive full protection under the act.What then is the scope of federal land management

responsibilities for endangered species? Several previous

Bruce A. Stein (e-mail: bruce_stein@natureserve.org) is vice president and chief

scientist, Cameron Scott is a conservation data analyst, and Nancy Benton is

a project manager at NatureServe in Arlington, Virginia. © 2008 American

Institute of Biological Sciences.

Federal Lands and EndangeredSpecies: The Role of Militaryand Other Federal Lands inSustaining Biodiversity

BRUCE A. STEIN, CAMERON SCOTT, AND NANCY BENTON

The US government has multiple responsibilities for the protection of endangered species, many of them stemming from its role as the nation’s largestlandowner. To explore how endangered and imperiled species are distributed across the federal estate, we carried out a geographic informationsystem (GIS)-based analysis using natural heritage species occurrence data. In this 10-year update of a previous analysis, we found that theDepartment of Defense and the USDA Forest Service harbor more species with formal status under the Endangered Species Act (ESA) than otherUS agencies. The densities of ESA status species and imperiled species are at least three times higher on military lands—2.92 and 3.77, respectively,per 100,000 hectares—than on any other agency’s lands. Defense installations in Hawaii are especially significant; more than one-third of all ESAstatus species on military lands are Hawaiian. These findings highlight the continued importance of public lands for the survival of America’s plantand animal species.

Keywords: endangered species, biodiversity, federal lands, Department of Defense, natural heritage

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studies have examined the degree to which federal lands sup-port rare and endangered species. Our initial review of thisquestion, based on species locality data from the network ofstate natural heritage programs, found that only about halfof the 728 species that were federally listed at that time wereknown to occur on federal lands (Natural Heritage DataCenter Network 1993, Stein et al. 1995). Similarly, a USGov-ernment Accountability Office study based on estimates ofhabitat availability determined that between one-third andone-half of federally listed species did not occur on federallands (USGAO 1995). In a subsequent review using 1996data, we documented the presence of nearly three-fifths(59%) of federally listed species on federal lands (Groves etal. 2000). That analysis considered 1184 species that werelisted as threatened or endangered, or were proposed or can-didates for listing, under the act.Groves and colleagues (2000) also considered how the

presence of listed species varied across lands of themajor fed-eral land management agencies. Surprisingly, the Depart-ment of Defense (DOD), which manages just 3% of thefederal estate, emerged as harboring the greatest number offederally listed species.This result echoeswhat Flather and col-leagues (1994) found using different methods. The seem-ingly disproportionate significance of military lands forendangered species documented in our previous study hasplayed a key role in motivating the DOD to be proactive inits efforts tomanagemilitary lands in ways that both sustainbiodiversity and maintain military readiness (Boice 2006).

Beyond legally protected speciesAlthough plants and animals listed un-der the ESA represent one set of speciesat increased risk of extinction, they areby nomeans the nation’s only species ofconservation concern. Listings underthe act not only reflect biological needand conservation conditions but also aresensitive to such factors as shifts in pol-icy and availability of funding (Goble etal. 2005). Indeed, the pace of listingsunder the act has fallen sharply since thelate 1990s, reaching a nadir in 2003when just a single species (the plantPolygonumhickmanii) was added to thelist (figure 1).NatureServe conservation status

assessments represent an independentand complementary view of the ex-tinction risk facing US species (Steinet al. 2000,Wilcove and Master 2005).Plant and animal species are evaluatedon the basis of a dozen criteria that arecorrelated with extinction risk, such aspopulation numbers and trends, rangesize, and habitat specificity. Thismulti-factorial analysis is summarized and

expressed as ranks on a scale of 1 through 5, where 1 repre-sents species considered to be critically imperiled and 5 thosethat are considered abundant and secure.These conservationstatus ranks can be applied to a species across its entire range(i.e., at the“global”scale), as well as at national and state scales.As a result, the NatureServe global conservation status ranks(orG-ranks) represent an assessment of the overall extinctionrisk facing the species. Such assessments have been carried outfor more than 35,000 US species, including all vertebrateanimals and vascular plants, and many of the better knowninvertebrate groups; these assessments are available onlinethrough theNatureServe ExplorerWeb site (www.natureserve.org/explorer).The NatureServe status assessments provide a means to

identify species of conservation concern that may not belegally protected under the ESA, and thus they are usedwidelyby federal agencies, conservation organizations, and indus-try to target conservation and land-management efforts.These assessments also provide a means to identify oppor-tunities for stabilizing and protecting species, which mayhelp avert the need for listing and regulation under the ESA.

A 10-year reassessmentOur last comprehensive analysis of the role that federal landsplay in sustaining the nation’s endangered species was basedon locational data that were current as of 1996 (Stein et al.2000). Over the past 10 years, several changes have occurredthat make it timely to reassess the relative stewardship

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Figure 1. Listings under the US Endangered Species Act. The pace of listings underthe ESA has varied considerably over time, primarily reflecting availability of fund-ing for listing activities and shifts in policy. As of October 2007 a total of 1333 USspecies and populations were listed as threatened or endangered under the act.Under the ESA, listings can apply to species, infraspecific taxa, or, for vertebrateanimals, “distinct population segments.” Source: US Fish andWildlife Service,Threatened and Endangered Species System, October 2007.

responsibilities of different federal land-management agen-cies with respect to listed species and other species at risk.First, considerable attention has focused in recent years on

the ESA itself,with a number of proposals being put forwardfor changes as part of a long overdue reauthorization of theact.Many of these changes relate to howESA protections andimplementation should relate to private lands, but a numberof important issues also under consideration are related to im-plementation of—and exemptions from—provisions of theact by various federal agencies, including the DOD. Second,the number of species listed under the act has continued toincrease, albeit at a diminished pace. As of December 1996,1078 US species were listed under the act; in October 2007,1333US species were listed, an increase of 24%.Third, in thepast decade a considerable amount of new inventorywork onfederal lands has been incorporated into state natural heritageprogramdatabases. Finally,many changes have taken place onthe landscape itself, both on and off public lands.

MethodsNatureServe coordinates a nationwide network of statenatural heritage programs, each of which maintains a data-base of documented populations of species of conservationconcern. These state-based inventories manage their dataaccording to common standards and protocols, enablingNatureServe to assemble a nationally consistent dataset ofprecise localities (“element occurrences”) for endangeredand imperiled species. We used this nationally aggregatedoccurrence data set as the basis for our analysis of species dis-tributions across federal lands.Although our previous analy-ses of endangered species on federal lands used earlier versionsof this same data set, they relied on landowner attribute dataincluded in each occurrence record.This was necessary at thetime because the occurrences were managed as point locali-ties rather than as polygon footprints.The current generationof natural heritage software (Biotics 4) provides geographicinformation system (GIS) functionalities that allowoccurrencerecords to be managed as spatially explicit polygons. Thesepolygons take into account both the footprint of the biolog-ical feature (where it is known) as well as estimates of spatialuncertainty.Our analysis was conducted in two stages.We first carried

out aGIS-based analysis comparing natural heritage locationaldata for imperiled and endangered species with a coverage offederal land holdings. These preliminary findings were thenreviewed by state natural heritage or federal agency biologists,and in the case of species with ESA status, vetted againstagency-generated endangered species lists.We used the US Geological Survey (USGS) federal lands

data layer (www.nationalatlas.com) as the federal lands cov-erage for the continental United States (the lower 48 states andAlaska).Althoughmore detailed data layers are available forspecific states, theUSGSdata layer is considered to be themostcomprehensive and consistent nationwide coverage for fed-eral lands.The only exception to our use of theUSGSdata lay-ers was for Hawaii, where issues of scale and registration,

coupled with the extremely localized distribution of manyspecies, led us to rely instead on higher resolution data fromthe Hawaii Gap Analysis Program (www.higap.org). For ouruse of the USGS federal lands data layer, we downloadedand merged the line and polygon layers. Because our inter-est was in the five major land management agencies (USDAForest Service, BLM,NPS,USFWS, and DOD),we excludedseveral otherminor federal land classes fromour analysis (table1).With the exception of the DOD, for which we wished tocarry out more detailed analyses, spatial units for each ofthe major land-management agencies were dissolved intodistinct polygon classes.

Species selection criteria. Consistent with our previousanalyses, our selection of species with federal status includedall taxa listed as endangered or threatened under the ESA orthat are proposed or candidates for listing under the act.(We refer to these collectively as “ESA status species.”) Thisincludes full species as well as infraspecific taxa (e.g., sub-species) and distinct population segments as recognized bythe act. In total, 1520 taxamet our criteria for species with ESAstatus. Our selection criteria for imperiled species includedspecies and infraspecific taxa assessed byNatureServe as crit-ically imperiled or imperiled across their range (G-rank=G1,G2, T1, or T2). To avoid biases resulting from inclusion ofspecies groups that are not consistently available in the statedatabases, our analysis of imperiled species included only ver-tebrate animals and vascular plants.A total of 3069 taxametour criteria for imperiled species (table 2). The two sets ofspecies—listed and imperiled—are not mutually exclusive.Because our interest here is in understanding the current

stewardship responsibilities of the different federal agencies,only species occurrences that have a reasonable likelihood ofbeing extant were included in this analysis. As a result, pop-ulations for species known or suspected to be extirpated ina given state (S-rank = SX or SH) were excluded, as werespecific populations known or suspected to be extirpated(EO rank = X or H). Consistent with our previous analyses,we also excluded older population occurrences, defined asthose not reverified since 1970. In total, more than 60,000

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Table 1. Area of land managed by federalagencies.

HectaresAgency (millions)

Bureau of Land Management 104.4

USDA Forest Service 78.1

US Fish and Wildlife Service 38.8

National Park Service 33.8

Department of Defense 12.1

Note: Because of their smaller land bases, two federalagencies, the Bureau of Reclamation (3.5 millionhectares) and Tennessee Valley Authority (0.1 millionhectares), were not included in this analysis.

occurrences of ESA status species and 55,000 occurrences ofimperiled species met our selection criteria.

Spatial analysis criteria. Because not all occurrence poly-gons nest completely within individual land-managementunits, we developed explicit decision rules for assigningspecies occurrences to agency landholdings.These criteriaweredesigned tominimize type I errors,where a speciesmight beerroneously reported for a land unit on which it does notactually occur.

Subsumed polygons. A species was assigned to a land-holding if an occurrence polygon of the species fell com-pletely within the unbuffered boundaries of the landmanagement unit.

Overlapping polygons. If an occurrence polygon over-lapped but was not entirely within the unbuffered boundariesof a land-management unit, we considered the precision ofthe record in evaluating whether to include or exclude thespecies fromour counts for that agency’s lands. For locationsknown to have beenmappedwith a high degree of precision(representational accuracy = high or very high), any amountof overlapwas considered sufficient for inclusion. For less pre-cise occurrence polygons, we required an overlap of at least50% before including the occurrence in our species counts.To further reduce type I errors in our counts of federallylisted species, before including species known on an agency’sland only from such partially overlapping polygons, we re-quired an independent validation during the review process.

Data review procedures.On the basis of our spatial analysisdecision rules, we identified a number of “questionable”species with respect to their assignment to lands of a givenagency.Our data review procedures focused on determiningwhich of these questionable species could reasonably beattributed to federal agency lands on the basis of other forms

of documentation.Lists of such questionable species were gen-erated for each state and provided to natural heritage programbiologists for review. Species were included in agency countswhere these biologists could positively confirm their presenceon agency lands. In some cases, species with well-known dis-tributions could also be confidently excluded as not occur-ring on an agency’s land.A second step in the review processinvolved federal agency input or review. Each federal agencyincluded in the analysis was invited to provide a list of speciesthought to exist on their lands or to review our preliminarylist in order to validate (or refute) the presence of such ques-tionable species. Agency-provided lists served as a valuablecross-check, but these lists do not necessarily coincide withthe criteria used in this analysis. For example, many listsinclude species that historically occurred but no longer arepresent on those lands. Discrepancies were investigated andconsidered on a case-by-case basis.

Caveats. This analysis is sensitive to several factors. First,although the data gathered and managed by state naturalheritage programs are widely considered to be themost com-prehensive available for rare and endangered species locations,these data generally are not the result of systematic invento-ries. The state databases incorporate data from a variety ofsources, including targeted inventories carried out by naturalheritage biologists, and collection and observation data fromthe broader biological community. Natural heritage data-bases generally reflect the state of biological knowledge for thespecies reported, including gaps in such knowledge. Inventorydata, however, appear to be more complete for public landsthan for private lands (Cutko et al. 2008), although some agen-cies may be underrepresented because of restrictive collect-ing policies (e.g., the NPS).The distributions formany of these rare species are highly

localized, so even minor errors in land boundaries can in-fluence the analysis. These issues are well illustrated by EglinAir Force Base, an installation in northwestern Florida withfairly well-documented flora and fauna. An anomaly de-tected during our data review revealed that the USGS landcoverage erroneously attributed the base’s coastal barrierislands to the NPS. This boundary error had the effect ofexcluding three federally listed species from our tally forEglin: perforate reindeer lichen (Cladonia perforata), thegreen turtle (Chelonia mydas), and the loggerhead turtle(Caretta caretta). Those boundary issues that came to lightwere corrected, but clearly in a national-scale analysis wewould expect others to go undetected.

Species across the federal landscapeFederal lands provide habitat for a considerable number ofrare and endangered species, and are likely to play an in-creasingly important role in sustaining the nation’s comple-ment of plants and animals. How federal agencies dischargethose stewardship responsibilities depends on their man-dates and statutory obligations, as well as on the nature of theresources they are called upon to manage.

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Table 2. Number of species included in theanalysis of ESA status species and imperiledspecies on federal lands.

Classification Number

ESA status speciesLichens 2

Invertebrates 313

Vertebrates 374

Vascular plants 831

Total ESA status 1520

Imperiled speciesVertebrates 383

Vascular plants 2686

Total imperiled 3069

Note: ESA status species include taxa that are listedunder the Endangered Species Act as endangered orthreatened, or that are formally proposed or candidatesfor listing under the act. Imperiled species include taxaassessed by NatureServe as critically imperiled (G1 orT1) or imperiled (G2 or T2).

This updated analysis indicates thatlands of the USDA Forest Service andthe DOD share the distinction of sup-porting the greatest number of specieswith formal status under the ESA.Landsof both agencies harbor about 23% ofthe ESA status species included in ouranalysis, with each agency hosting atleast 355 such species (figure 2). Thesetwo agencies are followed by the NPS(19%), theUSFWS (18%), and theBLM(16%), respectively.We should empha-size that because of the restrictive cri-teria used in our spatial analysis, thesefigures represent aminimumnumber oflisted species that currently exist onthese land holdings.In contrast to the pattern for ESA

status species, Forest Service lands by awide margin harbor the most Nature-Serve-defined imperiled species, with27% of the total number analyzed, ac-counting for at least 821 species (figure2). The BLM ranks secondwith 20%ofthe total, followed by military landswith just 15% of imperiled species.These updated figures for both ESA

status and imperiled species generallyare consistent with the results of our previous analysis, basedon 1996 data (Groves et al. 2000). For ESA status species,mostagencies displayed only modest increases—between 1 and2 percentage points—although both the Forest Serviceand the USFWS showed increases exceeding 5% (table 3).Increases in representation of imperiled species were ingeneral less than that for ESA status species, ranging from alow of 0.2% for the DOD to a high of 1.5% for the USFWS.Although the overall number of species occurring on an

agency’s lands offers an important perspective on relativestewardship responsibilities, thismeasuremasks the vast dif-ferences in area undermanagement of the different agencies.BLM lands, for example, cover 104million ha, an area nearlynine times the size of theDOD’s 12million ha.Analyzing the

concentration or density of species per unit area provides analternative perspective on stewardship responsibilities thatnormalizes for size differences. Based on a calculation ofnumber of species per unit of area,DOD lands stand outwith2.92 ESA status species and 3.77 imperiled species per 100,000ha (figure 3). By this density measure, the significance ofmilitary lands exceeds that of any other agency by a factorof three. Lands of the NPS,which cover about 34million ha,have the second highest concentrations of both ESA status andimperiled species (0.84 and 1.26, respectively).

A focus on the militaryGiven the disproportionate significance of DOD lands forendangered species, we explored their distribution across

military lands in greaterdetail. At the service level,army lands harbor morethan twice the number ofspecies of concern (15%ofESA and 9%of imperiled)as those of the navy (7%ESA and 4% imperiled),which had the secondhighest number (figure 4).Installations from each ofthe services are representedamong the top 10 for num-ber of both ESA status

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Figure 2. Distribution of endangered and imperiled species on federal agency lands.Lands of the DOD and USDA Forest Service harbor the greatest number of specieswith status under the Endangered Species Act (23%), while Forest Service landssupport the largest number of NatureServe-assessed imperiled species (27%). Source:NatureServe Central Databases (based on data from US natural heritage programs),February 2007. Abbreviations: BLM, Bureau of LandManagement; DOD, Depart-ment of Defense; FS, Forest Service; NPS, National Park Service; USFWS, US FishandWildlife Service.

Table 3. Comparison of the percentages of ESA status species and imperiled species on federallands, 1996 and 2007.

ESA status species Imperiled species(percentage) (percentage)

Agency 1996 2007 Change 1996 2007 Change

Bureau of Land Management 14.7 16.2 1.5 19.5 20.2 0.7

Department of Defense 21.0 23.4 2.4 14.7 14.9 0.2

Forest Service 18.1 23.4 5.3 26.3 26.8 0.5

US Fish and Wildlife Service 12.8 18.2 5.4 6.5 8.0 1.5

National Park Service 16.8 18.7 1.9 13.3 13.9 0.6

Note: These figures represent the percentage of total ESA status species and imperiled species documented onfederal agency lands in our previous analysis (Groves et al. 2000) using 1996 data, and by the current study using2007 data.

species (table 4) and imperiled species(table 5).Army bases, however, consti-tute 4 of the top 10 installations forESA status species and 5 of the top 10for imperiled species.A key question regarding the overall

ranking of military lands is whetherthese patterns are based on biologicalfactors, or whether these lands are sim-ply better inventoried than the lands ofother agencies. The relatively modestsize of the landholdings of theDOD, atleast compared with the Forest Serviceand the BLM, does make comprehen-sive inventoriesmore tractable, and themilitary has sponsored a considerableamount of inventory work on its in-stallations over the past two decades.Acomparison of the location of militaryinstallations with known hotspots ofrare species (e.g., Dobson et al. 1997,Flather et al. 1998,Chaplin et al. 2000),however, lends credence to the under-lying biological significance of themil-itary’s land holdings.The Hawaiian islands, in particular,

play an important role in the DOD’soverall ranking.This chain of oceanic is-lands is well known for its high levels ofendemism,many extremely rare species,and large number of species extinctions(Wagner and Funk 1995). Just threefederal agencies manage significantamounts of land in Hawaii: the NPS,USFWS, and DOD.Although the NPSadministers the largest areas—includingHawai‘i Volcanoes National Park andHaleakala National Park—the DODmanages more discrete land units. Be-cause of the highly localized ranges ofmany Hawaiian plant and animalspecies, the presence of multiple, dis-persedmilitary installations has the ef-fect of increasing the number ofdifferent species found onDOD lands.It is noteworthy that four of the topfive military installations for both ESAstatus species and imperiled species arelocated in Hawaii (tables 3, 4), lead byOahu’s Schofield Barracks MilitaryReservation,which supports at least 47species with federal status and 53 im-periled species.Overall,more than one-third (34%) of species with ESA statusfound onmilitary lands nationwide areHawaiian.

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Figure 3. Density of endangered and imperiled species on federal agency lands. Cal-culating the density of species per 100,000 hectares highlights the disproportionaterole that DOD lands play in sustaining the nation’s biodiversity. Military lands havethree times higher densities of ESA status and imperiled species than do lands of theNPS, the second-ranked agency for densities of both ESA and imperiled species.Source: NatureServe Central Databases (based on data from US natural heritageprograms), February 2007. Abbreviations: BLM, Bureau of LandManagement;DOD, Department of Defense; FS, Forest Service; NPS, National Park Service;USFWS, US Fish andWildlife Service.

Figure 4. Distribution of endangered and imperiled species by military service. Armylands harbor more than twice the number of ESA status and imperiled species asthose of the navy, which supports the next highest number. Source: NatureServeCentral Databases (based on data from US natural heritage programs), February2007.

Patterns of listed versus imperiled speciesWhat do the differences in patterns exhibited by listed speciesrelative to imperiled species tell us about how well we areprotecting species at risk? To address this question, one firstmust consider the relationship between these two statusdesignations.Master and colleagues (2000) found that 90%ofspecies listed at the time under the ESA also were categorizedbyNatureServe as imperiled species (G1,G2) or subspecies (T1,T2). Conversely, only a small fraction of the more than 4500species that have been assessed as imperiled byNatureServe arelisted under the ESA (Wilcove andMaster 2005).We found thevariance among agencies for imperiled species to be muchgreater than for listed species (table 3). Specifically, there is aspread of 19% between the agency with the greatest numberof imperiled species (Forest Service) and the least (USFWS).In contrast, there is only a 7% interagency variance for ESAstatus species.The BLM exhibits the greatest disparity in its rankings for

ESAand imperiled species.TheBLMlandshave the fewest ESAstatus species, yet the agency ranks second for number of im-periled species.TheBLMmanages vast areas of land in thewest-ernUnited States andAlaska.AlthoughAlaska is not known forsupporting largenumbersof rare species,BLMlands in thewest-ern United States contain many specialized habitat types thatsupport locally endemic species,whichnodoubt contributes to the large number ofimperiled species documented from theagency’s lands. It is therefore puzzling thatESA species are not aswell represented onthe agency’s lands, particularly given theenormous size of that land. Perhaps be-causemany of these lands are remote andreceive relatively little public attention,de-clining species onBLM lands are less likelyto enter (or emerge from) the pipeline forESA listing consideration.This disparity isparticularly noteworthy in view of theintense current pressures on BLM landsconcerning oil and gas exploration andextraction.

The federal role in managingat-risk speciesThe federal government has both regu-latory and land-management responsi-bilities in connectionwith the protectionof wildlife species. The USFWS and theNational Marine Fisheries Service havestatutory responsibilities for managingand protecting federal trust species, in-cluding those protected under laws suchas the ESA, theMarineMammal Protec-tion Act, and the Migratory Bird TreatyAct. Because wildlife resources are con-sidered public trust resources, regula-tions under these acts generally apply toboth public and private lands. Defini-

tions of “wildlife”variously include or exclude plants, and asnoted previously, plant species do not receive full protectionunder the ESAonprivate lands. Similarly, plantswere excludedfrom consideration as“species of greatest conservation need”in the federally funded state wildlife action plans, althoughsome states voluntarily included themwith nonfederal fund-ing (Stein and Gravuer 2008). The nation’s flora is an im-portant aspect of our biological heritage, and plants representmore than half (57%) of all US species currently listed underthe ESA. Given the diminished protections afforded thesespecies off the federal estate, the long-term survival ofendangered and threatened plant species are particularlydependent on the management of federal lands.Our results confirm the importance of Forest Service

lands for maintaining the nation’s complement of flora andfauna. Forest Service lands harbor asmany ormore ESA andimperiled species than any other agency. Given the largenumber of at-risk species found on Forest Service landsthat are not legally protected under the ESA, we are en-couraged by the inclusion in new forest planning rules of arequirement that new forest plans explicitly take into accountnot just listed species but also those with NatureServestatuses of critically imperiled, imperiled, or vulnerable(USDA FS 2005).

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Table 4. Top 10 military installations for ESA status species.

Number ofRank Service Installation State ESA species

1 Army Schofield Barracks Military Reservation HI 472 Army Makua Military Reservation HI 393 Navy Lualualei Naval Reservation HI 384 Army Pohakuloa Training Area HI 175 Marine Corps Marine Corps Base Camp Pendleton CA 176 Navy San Clemente Island Range Complex CA 107 Air Force Eglin Air Force Base FL 108 Air Force Vandenberg Air Force Base CA 109 Army Fort Lewis Military Reservation WA 1010 Air Force Avon Park Air Force Range FL 10

Note: These figures, based on documented occurrences in natural heritage databases, represent theminimum number of species on these installations.

Table 5. Top 10 military installations for imperiled species.

Number ofRank Service Installation State imperiled species

1 Army Schofield Barracks Military Reservation HI 532 Army Makua Military Reservation HI 463 Navy Lualualei Naval Reservation HI 444 Army White Sands Missile Range NM 335 Army Pohakuloa Training Area HI 246 Navy San Clemente Island Range Complex CA 247 Army Fort Hunter-Liggett CA 188 Air Force Eglin Air Force Base FL 159 Air Force Vandenberg Air Force Base CA 1310 Marine Corps Marine Corps Base Camp Pendleton CA 13

Note: These figures, based on documented occurrences in natural heritage databases, represent theminimum number of species on these installations.

Although theDODnow shares with the Forest Service thedistinction of having the greatest number of federally listedspecies, it remains clear that military lands have a dispro-portionate importance to the nation’s rare and endangeredspecies. This is seen most dramatically in the high concen-trations of imperiled and listed species on military lands(figure 3). Although conflicts sometimes exist between themilitary’s use of these lands and protection of endangeredspecies, the two have found a balanced coexistence at agrowing number of installations. Indeed, the maintenanceof natural habitats and native biodiversity is increasinglyviewed as important for providing realistic military trainingexperiences (Leslie et al. 1996, Benton et al. 2008). At FortBragg in North Carolina, for example, the type of openunderstory longleaf pine forest preferred by the threatenedred-cockaded woodpecker also turns out to be ideal for con-ducting army training exercises and maneuvers. By activelyrestoring these forests with prescribed burns, and carryingout other on-base and off-site conservation measures,natural resource managers have been able to accommodateboth endangered species protection and intensive militarytraining (Beaty et al. 2003).About 890,000 ha of open space a year are being lost to

development nationwide (NRCS 2003), putting increasedpressure on remaining wildlife habitat. In many parts ofthe country, development is expanding rapidly into theso-called wildland-urban interface, fueled in part by thedesirability of living adjacent to public lands with perceivedhigh amenity values (Brown et al. 2005, Radeloff et al. 2005).This trend not only has the effect of diminishing wildlifehabitat adjacent to these public lands but also limitsmanagement options on the public lands themselves. Firemanagement, in particular, becomes vastlymore complicatedwhen housing is interspersed with formerly unpopulatednatural areas. Encroachment of private development alongthe edge of military installations is now recognized as athreat not just to wildlife habitat but to military operationsas well. Perhaps no place illustrates this more vividly thanalong the coast of southern California, whereMarine CorpsBase Camp Pendleton stands as the only significant naturalbuffer between the sprawling metropolises of Los Angelesand San Diego.Given the current and projected pace of private land de-

velopment, we can expect that federal lands will assumegreater importance for the protection of our native species.At the same time, public lands are under increasing pressureto produce energy, fiber, and other resources, a push that hasled to the relaxation of some environmental safeguards.This reassessment of the role of federal lands for endangeredand imperiled species provides clear evidence of theimportance of public lands as reservoirs of biodiversity.While the nation’s biological heritage cannot bemaintainedon federal lands alone, how these public trust lands aremanaged will be a major determinant of our success at sus-taining America’s rich diversity of wildlife.

AcknowledgmentsThis study was carried out with funding from the DODLegacy Resource Management Program under CooperativeAgreement #W912DY-06-2-0004.We thank Peter Boice andJaneMallory of the Legacy office for their support for this re-search.Marcos Robles, LynnKutner,KatMaybury, and JasonMcNees all provided valuable assistance to this study. Dou-glas Ripley generously provided comments on the manu-script. We thank the following federal agency staff whoprovided agency species lists for use in our data review:StevenG. Fancy,Gary Krauss,Alison Loar, Steve Lydick, JaneMallory, andDavid Pivorunas.The species locational data onwhich this study was based derive from state natural heritageprograms in each of the 50 states, and collectively representthe efforts of many hundreds of natural heritage biologists aswell as many thousands of field observers and contributorsfrom universities, museums, state and federal agencies, andthe private sector.We are grateful to the staff of these naturalheritage programs, and particularly to the following indi-viduals who assisted us with this study: Doug Backlund,Jeannie Barnes, John Baxter, Sara Cairns, Stephanie Chance,LynnDavidson,ChristineDirk,RitaDixon, John Fleckenstein,Heather Foley, Raquel Goodrich, RonHellmich, BrianHen-derson, Sara Hines, Dan Hipes, Julie Holling, MelanieHowarter, Daryl Howell, Susan Jeffers, Ann Johnson, KrisJohnson, Roy Kam, Susan Klugman, Greg Krakow, SarahLindsey, Nicole Lorenz, Dwight Matsuwaki, Bryce Maxell,Rayo McCollough, Darlene McGriff, Jack McMillen, JulieMichaelson, Eric Miskow, Cindy Osborne, Aditya Peri, AlanRedder, Megan Rollins, Barbara Sargent, Eric Scheuering,Greg Schneider, Sabra Schwartz,David Szczebak, Phil Tonne,Sue Vrilakas, GlennWoodsum, and Karen Zyko.

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