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I E W
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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