Disturbed systems provide evidence for the function of biota in creating resilience
to disturbance. Thus, intact eucalypt forest in Australia supports many species of coex-
isting endemic honeyeaters. In contrast, the noisy miner (Manorina melanocephala),
the geographical replacement to the bell miner mentioned in Section 21.6.1,
dominates the bird community in fragmented forest in which an open canopy has
developed through a combination of logging, persistent livestock grazing, and
agriculture. The noisy miner aggressively excludes most of the smaller honeyeaters.
Consequently, exposed trees suffer chronic infestations of psyllids, dieback of their
main limbs, and death. In essence, exposed trees are no longer viable due to the dearth
of insectivorous birds (Landsberg 1988; Grey et al. 1997, 1998).
We still need to evaluate whether it is the biodiversity itself (richness) or the com-
position of the community that is important, that is, whether who is present is as
important as how many species are present (Srivastava and Vellend 2005). Much still
needs to be done to determine whether biodiversity alters the processes within ecosys-
tems and if so what the mechanisms are. Nevertheless, evidence is accumulating to
suggest that where ecosystem processes have been ignored or distorted they can lead
to perverse effects for both ecosystems and individual species, and expensive reme-
dial action for conservation (Schwartz et al. 2000; Hector et al. 2001).
Management of populations has to take into account that they are embedded within
a matrix of other competitors, predators, and prey. These form the community and
their environments. Thus, we need to consider the management of individuals,
populations, and species in the context of the ecosystem. The main points are:
1 Ecosystems involve long-term events related to the environment. Management needs
to account for infrequent and unpredictable events, such as earthquakes, hurricanes,
floods, fire, and droughts.
2 These events provide insight into mechanisms of ecosystem regulation and stabil-
ity. The term “long term” is a function of the slowest variable in the system and is
not related to the life history of the organisms concerned. Management should main-
tain these regimes either naturally or by mimicking their effects. Planning should
consider natural periodicities from the very long term (200 years for earthquake and
fire cycles) to the short term (of a few years for the effects of the El Niño Southern
Oscillation and the North Atlantic Oscillation). Thus, the periods of both unpredictable,
sudden events and slow change dictate the time scale for conservation planning. In
most cases planning should be for 30–50-year periods or longer.
3 Ecosystem management needs to consider that there are slow trends due to envir-
onmental change, plant succession, and animal population fluctuation. These slow trends
show an interaction between abiotic and biotic processes, each affecting the other.
4 Ecosystems should be managed at an appropriate spatial scale. Small patches of
forest are insufficient to support viable populations of predators such as northern
spotted owls (Strix occidentalis). Large areas are required for migrating ungulates
moving between summer and winter ranges. Sufficient area is required to produce
the mosaic of burns of different age. This mosaic from disturbances creates habitat
heterogeneity that is used as sources and sinks for animals. Sinks are required as
holding areas for non-breeding animals waiting to obtain territories.
5 Management of target populations, such as pest species, can result in indirect inter-
actions through hyperpredation, apparent competition, and meso-predator release.
These can produce unexpected consequences.
ECOSYSTEM MANAGEMENT AND CONSERVATION 383
21.15 Summary
