Paul's questions: predation is good

Glenn Morton (GRMorton@gnn.com)
Sat, 20 Jul 1996 21:44:12

Hi Paul,

I started a new thread so as not to disturb your Christ and Creation one.

You wrote:

>If creationists are wrong, then I believe that TE must answer several
>questions ... i.e. how to account for regular, destructive "natural"
>processes in Christ's good creation and what natural processes are in
>fact sufficient to provide the "holding together" required?
>

Usually this type of question is aimed at the predation and death of
animals before the Fall. We assume that a world without predators is
better than our world. This is not true. I would like to point out that
predation is good. And God uses it to increase the number of species
which can live on the earth.

Consider the following:

"More recent studies of natural communiteis have largely confirmed
the hypothesis that predators may actually increase the number of
different species that can live in a habitat. The American ecologist
Robert T. Paine made an especially fine study on the animal community of a
rocky shore on the Pacific coast of North America. The community included
15 species, comprising acorn barnacles, limpets, chitons, mussels, dog
whelks and one major predator, the starfish Pisaster ochraceus, which fed
on all the other species. Paine carried out an experiment on the small
area of the shore in whihc he removed all the starfish and prevented any
others from entering. Within a few months 60-80 per cent of the available
space in the experimental area was occupied by newly-settled barnacles,
which began to grow over other species and to eliminate them. After a
year or so, however, the barnacles themselves began to be crowded out by
large numbers of small, but rapidly growing mussels, and when the study
ended these completely dominated the community, which now consisted of
only eight species. The removal of predators thus resulted in the halving
of the number of species and there was evidence, too, that the number of
plant species of the community (rock-encrusting algae) was also reduced,
because of competition with the barnacles and mussels for the available
space."
"A general conclusion then is that the presence of predators in a
well- balanced community is likely to increase rahter than reduce the
numbers of species present, so that overall, predators broaden the
distribution ofspeacies. Only a few experiments similar to Paine's have
been performed and so one must be cautious about applying this conclusion
to all communities. There is some independent evidence, however that
herbivores, which act on plants as predators do on their prey, may
similarly increase the number of plant species that can live in a habitat.
In the last century, Charles Darwin noticed that in southern England,
meadowland grazed by sheep often contained as many as 20 species of
plants, while neglected ungrazed land contained only about 11 species. he
suggested that fast- growing, tall grasses were controlled by sheep
grazing in the meadow, but that in ungrazed land these species grew tall
so that they shaded the small slow-growing plants from the sun and
eliminated them. A similar process occurred in chalk grassland areas in
Britain, when the disease myxomatosis caused the death of large numbers of
rabbits; the resulting reduction in grazing allowed considerable invasion
by coarse grasses and scrub. As a result many of these areas are much
less rich in species than they were under heavy 'predation'.
"On the Washington coast, Paine performed another series of
experiments in which he removed the sea-urchin Strongylocentrotus
purpuratus, which grazes on algae. Initially, there was an increase in
the number of species of algae present; the six or so new species were
probably ones that were normally grazed too heavily by the sea-urchin to
survive in the habitat. But over two or three years the picture changed
as the community of algae gradually became dominated by two species,
Hedophyllum sessile on exposed parts of the shore, and Laminaria
groenlandica in the more sheltered regions below low-water mark.
These two species were tall and probably 'shaded out' the smaller species,
as did the tall grasses studied by Darwin. The total number of species
present was in the end greatly reduced after the removal of the
herbivores."~C. Barry Cox and Peter D. Moore, Biogeography, (Boston:
Blackwell Scientific Publications, 1985), p. 92-93

and

" The interactions may be quite complex, however, as in the case of the
Hawaiian damselfish, which is a predator of coral reef habitats. In an
experimental study of the influence of this fish, plates were constructed
which were suitable for algal colonization, and these were placed in three
types of location. (1) within cages which excluded all herbivorous
fishes, (ii) uncaged, but within the territories of the carnivorous
damselfish, and (ii) uncaged and placed outside damselfish territories.
The diversity of the colonizing algae was highest on the uncaged plates
inside damselfish territories and least in the uncaged samples outside the
territories. In other words, where there was no grazing at all, the algal
diversity was higher than when there was intense grazing, but the highest
diversity was found in sites where grazing was controlled to an extent by
the predation of the damselfish upon the grazers."~C. Barry Cox and Peter
D. Moore, Biogeography, (Boston: Blackwell Scientific Publications, 1985),
p. 93.

Predators play a crucial, God-given role in holding the creation together.
They keep overpopulation from occurring.

glenn