Conservation of endangered species - Ecological Applications: Toward a Sustainable World - page 109

recognize that small populations may also be at risk because of low genetic diversity and inbreeding
depression
realize that every conservation question also has an economic angle and usually a sociopolitical
one too

5.1 Dealing with
endangered species
- a crisis discipline

The population of white-backed vultures ( Gyps bengalensis ) in India has declined
by more than 99% in less than a decade. You would be lucky to see one today where
just a few years ago thousands were carrying out their daily refuse disposal business.
Vultures may not be your favorite birds, but to Jijanji they are a vital part of everyday
life. ' Nowadays, dear sir, it is not unusual to see a dead buffalo rotting into a stinking
mess close to where children are playing. Contamination of nearby wells and the spread
of disease by fl ies must surely be more likely now that dead animals are not quickly
picked clean by the vultures .' Jijanji fears that the white-backed vulture, together with
its long-billed ( G. indicus ) and slender-billed cousins ( G. tenuirostris ), could be
extinct within a few years. This is a crisis whether you are a conservationist or part
of the local community that depends on the vultures for waste disposal. But to Jijanji
the crisis is even more personal. He is a Parsee, a descendant of Persian refugees
who settled long ago in western India. ' According to my religion dead people should
not be buried, burnt or thrown into river or ocean, because of the sacredness of earth,
fi re and water. Instead, within a few hours of death a Parsee is taken in daylight to a
special tower (dakhma) where the naked body is laid on a platform in full view of vul-
tures. The corpse is completely stripped within an hour or two, according to our rites,
but only if the vultures are there .'
In the previous section of the topic (Chapters 2-4), my focus was the application
of ecological theory at the level of the ecology of individuals (niche theory, life-
history theory, dispersal/migration theory). The individual organisms of a single
species are collectively known as a population. In this chapter and the two following
I shift attention to the application of ecological theory at the level of populations .
When confronted with a declining population, such as that of the white-backed
vulture, managers need to invoke the theory of population dynamics, which seeks
to understand what determines population size and the way this varies through
time. In simple terms, a population's dynamics depend on the interplay of processes
that increase (birth and immigration) or decrease population size (death and emi-
gration) (Box 5.1). You will discover in the next two chapters that the theory of
population dynamics is also the key to success in pest control operations (Chapter
6) and the management of wild harvests (Chapter 7). The 'theory' boxes of all three
chapters (Boxes 5.1, 6.1 and 7.1) can be read together as an overview of population
dynamics theory.
Population dynamics theory is one of the most mature of ecological disciplines,
but only relatively recently has attention been turned from the fundamental under-
standing of population dynamics to the application of theory to populations at risk
of extinction. Extinction has always been a fact of life - the fossil record tells us
that the vast majority of species that ever existed became extinct long ago. But the
arrival on the scene of humans injected novelty into the list of causes of extinction.
Overexploitation by hunting was probably the fi rst, but more recently many others
have been brought to bear, including habitat destruction, introduction of invaders