December. 1999 
5 
In principle, information and activities required 10 
conserve biological diversity docs not differ from that 
required to conserve most other resources That is one 
must know (I) the location of the resource. (2) the 
abundance of the resource; (3) changes in the abundance 
of the resource over time; and (4) factors responsible 
for changes in abundance in the resource over time 
The process ol documenting the location and relative 
abundance of biological diversity may be thought of as 
inventory, while that of identifying the temporal 
variation in biological diversity and factors responsible 
for this variation can be considered as ecological 
monitoring. 
IMPORTANCE OF ECOLOGICAL 
MONITORING FOR FOREST MANAGEMENT 
Ecological monitoring is important for forest 
management for a variety of reasons First, ecological 
monitoring can provide advanced warning of 
undesirable ecological change and thus permit managers 
to adopt an adaptive management approach to 
conserving biological diversity. Given the complexity 
of tropical forest ecosystems, following an adaptive 
management approach is essential Secondly, ecological 
monitoring is a necessity in ordci lu objectively evaluate 
whether project or protected area objectives of 
conserving biological diversity are being achieved One 
of the major short-comings of most of the early 
integrated conservation and development projects has 
been the absence of a comprehensive ecological 
monitoring program (Kronen el at., 1994). Thirdly, 
ecological monitoring is a necessity in order to evaluate 
the long-term impacts of human activities and 
disturbance on biological diversity This is particularly 
true because there is often a lag between a disturbance 
event and a subsequent response Fourthly, ecological 
monitoring can provide important insights into ihe 
functioning of complex ecosystems. Understanding the 
ecological dynamics of a forest is a perquisite to 
developing sustainable forest practices 
IMPORTANT CONSIDERATIONS IN 
DESIGNING AN ECOLOGICAL MONITORING 
PROGRAM 
Prior to implementing any ecological monitoring 
program, there must be clear objectives and hypotheses 
For the Eastern Arc forests, two obvious objectives of 
an ecological monitoring program are' ( I) to enhance 
the understanding of the ecological dynamics of the 
forests; and (2) to evaluate the Impact of human 
activities and disturbance on populations, species, 
communit'es, and landscapes. In relationship to the 
latter objective, a null hypothesis is that human activities 
do not adversely affect biological diversity while the 
alternative hypothesis is that human activities do 
adversely affect biological diversity 
ECOLOGICAL INDICATORS 
Identifying what to monitor can he simplified if 
indicators of various functional and organizational levels 
can be identified (Noss 1990. Hcllawcll 1991) 
Identifying species and suites of species which are 
representative of various functional groups (primary 
producers, primary consumers, secondary consumers, 
tertiary consumers) is a strategy which has been 
frequently advocated (Kremen a at. 1993. 1994) In 
many cases, the suitability of species or suites of species 
as indicators of change may need to be pretested In 
many tropical forests, epiphytes and orchids (Turner 
ei at. 1994). butterflies (Hill el at 1995), termites 
(Collins 1980), and dung beetles (Klein 1989). 
understory birds (Johns 1986. Ncwmark 1991. Thiollay 
1992) and primates (Skorpua 1986. Weisenscel et at 
1993) have been found to be particularly sensitive to 
human disturbance and thus arc useful indicators of 
ecological change 
CURRENT AND PROPOSED ECOLOGICAL 
MONITORING IN THE USAMBARAS 
Since 1987. I have been monitoring annually understory 
bird populations on an archipelago of nine forest 
fragments and an adjacent control site in the East 
Usambaras lu 1989. I initiated a parallel study on .i 
second archipelago of four forest fragments and an 
adjacent control site in the West Usambara* The broad 
objectives this research arc to evaluate the impact of 
forest fragmentation on understory bird communities, 
and to gain a greater understanding of the population 
dynamics ol tropical forest birds Specific objectives 
of this research arc to examine (I ) Ihe metnpopulanou 
dynamics of understory bird communities on two 
archipelagoes of forest fragments whose total size are 
nearly identical but whose fragments differ in average 
size and distance from a control site; «2) variation in 
understory bird survivorship, natality, and movement 
within the two archipelagoes and across individual forest 
fragments; (3) how temperature, humidity, 
luminescence, and vegetation structure varies from 
forest edge to the interior and its relationship to the 
distance that understory birds species arc encountered 
from the forest edge , and (4) the impact of past selective 
logging upon understory bird communities. (For more 
on this project see “Impact of Tropical Forest 
Fragmentation Upon Bird Populations in the Usambara 
Mountains, Tanzania. August 23toSepctembcr7. 1999" 
on page 15 of this issue.) 
Understory birds in the Usambara Mountains are 
quite sensitive to forest disturbance and thus appear to 
he good indicators of ecological change However our 
understanding of the dynamics of forest ecosystems and 
the impact of human disturbance on biological diversity 
could be enhanced if additional suites of species which 
are representative of other functional groups are also 
simultaneously monitored Efforts arc currently under 
way through the support of the MacArthur Foundation 
