7988

• UCREFRP Catalog Number: 7988
• Author: Lande, R.
• Title: Genetics and Demography in Biological Conservation
• USFW Year: 1988
• USFW - Doc Type: Science
• Copyright Material: YES

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estimates put the total population size of the northern sported owl at
2500 pairs (48). In western Oregon and Washington, the remaining
old-growth forest is restricted mainly to 12 national forests that arc
largely contiguous. To comply with the National Forest .Manage-
ment Act of 1976, which requires that native verrcbrate species be
maintained well distributed throughout their range on federal land,
the U.S. Forest Service developed a plan to preserve the northern
sported owl. Originally, this was based on the supposition that
protection from logging of territories for about 500 pairs distribut-
ed throughout the region would maintain enough genetic variability
for the population ro survive (23). However, models of stochastic
demography and habitat occupancy indicate that the plan is likely to
cause extinction of the owl because suitable habitat in the region will
be too sparsely distributed to support a population (49). An
independent assessment by the Forest Service also predicts extinc-
tion on demographic grounds, but essentially the same management
strategy remains in effect (50).
The red-cockaded woodpecker, Picoides borealis, ranges across the
southeastern United States, inhabiting pine forests more than about
80 years old, most of which currently exist on federal lands. Their
preferred habitat has substantial openings, and is maintained by
recurring fires that prevent succession to hardwoods. Thew birds
live in colonies, composed of one breeding pair and up to several
offspring serving as helpers, that occupy an annual home range
averaging about 215 acres in which they forage for insects. Nesting
occurs in cavities that may take a year for the birds to hollow out of
living, mature longleaf pines (80 to 120 years old) that have had
their heartwood destroyed by a fungus. The total size of the
breeding population was recently estimated to be 6000 individuals
(51). The recovery plan for the red-cockaded woodpecker, based on
genetic considerations, has as its goal the establishment of local
populations of 250 clans (500 breeding individuals) (24). The
species has been listed as federally endangered since the passage of
the Endangered Species Act in 1973, but subsequently has declined
rapidly throughout its range u a result of fire prevention and
logging of suitable, unoccupiet: habitat, which has severclv frag-
mentcd the remaining suitable habitat (51). For example, under
management by the U.S. Forest Service, populations on national
forests in Texas have been declining by about 10% per year (52).
Unless management practices arc drastically altered, it seems that the
red-cockaded woodpecker will soon be etrirla.
Scientific advisory panels reviewed the inadequacies of the man-
agement plans for the northern spotted owl and the red-cockaded
woodpecker and in both cases recommended abandoning simple
genetic rules for establishing minimum viable population sizes (48,
51). Management of particular species should incorporate details of
the species ecology, especially its life history and demography,
which may require larger populations than has been suggested on
genetic grounds alone.
Since conservation of the northern sported owl and the red-
cockaded woodpecker involves preserving habitats worth billions of
dollars to the lumber and paper industries, in principle there should
be no difficulty in funding long-term scientific studies to obtain the
information necessary for sound management decisions. Already a
great deal is known about both species. Why then does it appear that
the conservation plans for these species are unsuccessful? Short-term
economic and political interests often dominate scientific consider-
ations in the development and implementation of management
plans for threatened or endangered species. Whether economics and
politics continue to produce scientificallv deficient conservation
plans will be decided in manv cases only by extended litigation.
Future conservation plans should incorporate both deco aphv
T- genetics inIDassessing etheth regwrenrnts for species
sill 'rely" , ra)?ecognizing that tocKw[ld po ulaaons" do o _ap`(uc taaors

G
may usuallv be of more immediate im trance than genetic factors.
Alva lsnc mtegntuion o demography and pop on genetics,
applicable to species in natural environments, is a formidable task
that has enticed but largely eluded ecologists and evolutionary
biologists. The immediate practical need in biological conservation
for understanding the interaction of demographic and genetic
factors in the extinction of small populations therefore may provide
a focus for fundamental advances at the interface of ecology and
evolution.
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Lynch, Evolution 39, 804 (1985); M. Lynch, Genet. Res. 51, 137 (1988).
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22. U. S. Seal and T. Foose, J..t/init. Acad. Sn. 49, 3 (1983/84).
23. Final Regional Guide and Final Environmental Impact Statement fir the Pon_ht Northwest
Region (U.S. Forest Service, Portland, OR. 1984).
24. Red-cockaded Woodpecker Recovery Plan (U.S. Fish and Wildlife Service, Atlanta, GA,
1985).
25. F. W. ABendorf et al., Heredirat 91, 19 (1979); S. O'Brien et al., Sciew 221, 459
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Univ. Press, New York 1987), pp.-
ARTICLES
4-1 16 SEPTEMBER 1988 [459