ever, the very nature of tropical lower montane
forests—their great biodiversity, high degree of en-
demism, and insularity—makes them especially sus-
ceptible to the impoverishment of genetic diversity,
demographic stochasticity, and other problems that
plague small isolated populations and increase their
risk of extinction (Harrison 1994, Meffe and Carroll
1997).
The first step in conservation management is an
accurate species inventory of the area. Without base-
line data on the species present, it is impossible to
predict the risk of extinction or to recognize extinc-
tions when they occur. An inventory of the flora and
fauna of Monteverde is nearly complete for the more
familiar taxa, such as amphibians, reptiles, birds,
mammals, and plants (see Appendices). For many
other taxa, it has hardly begun (see Chap. 4, Insects
and Spiders). The MCFP and the Tropical Sciences
Center (TSC) may be the appropriate institutions for
facilitating and coordinating systematic species in-
ventories in the area.
The next step is to determine the current status of
populations and ecosystems—their sizes, structure,
and functions—and to implement a monitoring sys-
tem to detect changes in populations or ecosystems,
and to forecast future trends. At present, there is no
long-term system for monitoring populations and
ecosystems in Monteverde. The cost of a long-term
monitoring system is an immediate constraint. Be-
yond that, there is the problem of which species to
follow and what data to collect. No one questions that
an understanding of reproductive biology, nutritional
needs, demography, population age structure and ge-
netic structure, and population size is essential for
managing cultivated crops, domesticated animals,
game species, or endangered species (Lande and
Barrowclough 1987, Ruggiero et al. 1994). How can we
protect plant and animal species in Monteverde over
the long term in the absence of such information?
Young's study of House Wrens illustrates the potential
pitfalls of simply recording the occurrence of a species
rather than understanding its population dynamics. A
species may be present in a particular habitat and ap-
pear as if it is thriving, but conditions in the habitat may
be unsuitable because of insufficient food availability
or quality, or excessive predator or parasite pressure.
Populations can persist in such "sink" habitats only if
immigrants continuously arrive from "source" habitats
(Pulliam 1988; see Young, "House Wrens," p. 448).
There are some shortcuts for conservation manag-
ers that may provide reasonable interim protection
while we gather the information required for effective
long-term management. The concepts of indicator
species, keystone species, umbrella species, island
biogeography, metapopulation dynamics, and ecosys-
tem management have been particularly useful in con-
servation biology, all the more so because in conser-
vation decisions must often be made quickly with
insufficient data.
Changes in the behavior, population size, structure,
or function of a carefully selected subset of species
(or habitats) can serve as an early warning of threats
to other species or habitats. By focusing monitoring
efforts on a few indicator species, we may be able to
identify and mitigate environmental problems at an
early stage, before they become irreversible (Noss
1990). Of the hundreds of bird species in Monteverde,
thousands of plant species, tens of thousands of in-
vertebrate species, how do we select the most useful
indicator species? Indicator species should be chosen
after analyzing the species' natural history and popu-
lation dynamics, which should be sensitive to envi-
ronmental changes and representative of a broader
group of species. Dense, stable populations of aquatic
insects such as caddisflies indicate clean water, whereas
an abundance of sludge midges indicates eutrophica-
tion or other types of stream pollution (see Chap. 4,
Insects and Spiders, and Gill, "Impact of Lecheria,"
p. 446). Monitoring caddisflies and midges and measur-
ing stream water levels would provide a relatively low-
investment means of assessing water quality, hydrologi-
cal conditions, and aquatic biodiversity.
Although rare species should be monitored when
possible, they are unsuitable as indicator species.
Their biology is seldom representative of many other
species, and they are impractical to study because
they are difficult to find or because studying them
exacerbates their rarity. Instead, we should pick eas-
ily observable organisms as indicator species. They
should be common enough to provide adequate sam-
ple sizes for statistical analyses and to allow experi-
mental manipulations (transplants, removals, intro-
ductions, exclosures). Other key elements of sound
experimental design include randomization of treat-
ments and study plots, replication, controls, baseline
data, and continuity and longevity of the study. The
esthetics of doing field biology are also a consider-
ation, for how else can researchers be expected to
dedicate themselves to long-term, often tedious stud-
ies unless they enjoy the process (Wheelwright and
Smith 1994)?
Conservation biologists often have to resort to ex-
ploiting whatever data sets are available. Few long-
term monitoring programs exist in Monteverde; most
studies began as short-term undergraduate or gradu-
ate research projects designed to answer specific ques-
tions unrelated to conservation. Nonetheless, a pre-
liminary sense of the impact of recent climate changes
on reproduction in forest trees in Monteverde can be
obtained by examining the timing of flowering and429 Conservation Biology