Bias and biodiversity

5 Pages·1992·0.27 MB·English

by  W. F. Ponder

The publications which will emerge from ELLIOT, H. (ed), 1974. Serrmd World Conferrnce on Natknnl
Pnrkr: Yellowstow and Grand Telon N& Park, USA.
IUCN in the next two years generated by the
September 1&27, 1972, Proceedings. IUCN: Morges.
Caracas Congress will provide a cornucopia of
ideas, information, guidelines and practical MCNELLAY. ,AJN.D MILLER, K. R. (ed), 1984. NatwnalPark,
Cmmalim, and Dmelo~mmt:T he Rok o f Protcctcd Arem
assistance which will provide a springboard for
in Surlaining Socir~y. Smithsonin Institution Press:
improving the world's national parks and pro- Washington, DC.
tecied areas.
PENDLE.. G... 1976. A Hktw, o*f Lotin Amnica. Pen"w in:
London.
REFERENCES
WORLDC OMMISSIOONN ENVIRONMENANTD DEVELOPMENT,
ADAMSA, . B. (ed), 1964. Fin1 Wmld Confmce m Notiml 1987. Our Camm Fulure. Oxford University Press:
Park. US Government Printing Office: Washington, DC. Oxford.
Bias and biodiversity
W. F. Ponder
Australian Museum, Sydney
It is well known that the greatest threat to bio- The key to animal life is autotrophy - the
diversity is due to the rapidly expanding human conversion of inorganic substances into
population with its insatiable appetite for the organic. The most essential autotrophic process,
Earth's resources. The human plague and all as we all know, is photosynthesis - in which
its catastrophic side effects are perpetrating a living organisms are able to use the energy of
major extinction event. And yet what efforts sunlight to convert inorganic material (carbon
are being made to understand the real nature dioxide), into organic material. It occurs not
of the diversity that is being lost and the actual only in plants but also in many bacteria. Algae,
cost to us as living organisms? With around higher plants and some bacteria produce
only 5.2 per cent of our planet's land protected oxygen as a byproduct. Another, but less well
(Groombridge 1992), and an estimated 140 known, autotrophic process is chemosynthesis,
species in the tropics alone becoming extinct the production of organic matter from inorganic
every day (Ryan 1992), where do our priorities by means of chemical energy, which is limited
lie? Should we be more concerned about to certain groups of bacteria. Photosynthesis
diminishing koala numbers, destruction of and chemosynthesis are an essential part of the
rainforests, threats to the Great Banier Reef, cycling of elements and compounds upon
or soil erosion? which the entire biosphere depends.
Before attempting any such prioritization we Because as little as 1-15 per cent of plant
should ask a basic question - what organisms material is actually harvested by animals
play key roles in the fundamental processes in (Whittaker 1975), the other side of the auto-
ecosystems? We may then be able to assess the trophic coin is the vital necessity to decompose
kinds of losses that would cause the most dead organic material to make it once again
serious impacts. Much of the conservation available to the autotrophs, otherwise all
literature is dominated by work on vertebrates nutrients would be locked up in dead bodies.
and higher plants. Whereas higher plants play Bacterial and fungal activity is responsible for
an enormously important part in terrestrial most decompostion, although some is non-
ecosystems, in the marine sphere this is clearly biotic (e.g., fire). Thus the popular notion that
not so. Vertebrates are usually conspicuous, for ecosystems can be understood with food chains
example fishes in marine ecosystems, and starting with plants, followed by herbivores, and
birds, reptiles and mammals in most terrestrial ending with carnivorous animals is excessively
systems. But are they significantly involved in simplistic, ignoring the huge, necessary con-
any of the processes that might be called tribution by micro-organisms. In fact without
"fundamental"? To answer this question we their intestinal symbiont fauna and flora most
must go back to basic ecological principles. metazoans would be unable to function. Other
December 1992 Australian Zoologist, Vol. 28(14) 47
vital activities such as soil formation and The most abundant organisms are "microbes",
maintenance are also largely due to micro- which loosely include bacteria, viruses, single-
organisms. celled "algae" and protozoans. Although there
are only about 4 000 named bacteria and 5 000
Vertebrates are either not involved in, or
named viruses (including plasmids, phages
not essential for, any of these fundamental
etc.), estimates (e.g., Groombridge 1992)
processes. In fact, bacteria have been in
suggest there may be three million species
existence for about 3 400 million years whereas
of bacteria alone. As I have attempted to
the first animals are only 700 million years old.
show above, these organisms play crucial roles
Thus life has been maintained on earth for
in our ecosystems - like the photosynthetic
nearly five times longer than higher plants and
Cyanohacteria (commonly called blue-green
animals have been in existence.
"algae") which have a history reaching back
Not only are most of the specles and 2 500 million years and comprise thousands of
numbers of animals "invertebrates" (e.g., Beattie living species. Cyanohacteria were probably
et al. 1992) in most terrestrial communities responsible for changing the atmosphere
animal biomass is concentrated in "inverte- and making it possible for the "higher"
brates", not vertebrates, and in the sea most of life forms to evolve and are one of many
the biomass is in planktonic animals, not fish groups that comprise the "Bacteria" (Kingdom
(Whittaker 1975). Tiny animals can be found Prokaryotae or Monera). This diverse group-
in very high numbers, for example as many ing of immensely important organisms exist in
as 20 million nematodes per m2 (Overgaard- every environment capable of sustaining life.
Nielsen 1949, 1949a). A spoonful of soil is said to contain some
101° bacteria and the number of bacteria in
Is our preoccupation with vertebrates in eco-
your mouth is more than the number of people
logical and conservation priorities out of all
that have ever lived (Margulis and Schwartz
proportion to their ecological importance?
1988).
Vertebrates actually make up less than 1 per
cent of living species (Groombridge 1992) and Organisms as different as protozoans and
yet, by definition, only terrestrial vertebrates algae make up.another enormous group some-
(amphibians, reptiles, birds and mammals) are times considered to be a separate kingdom, the
recognized as "fauna" in New South Wales Protista or Protoctista, comprising 27 (Margulis
government legislation dealing with conserva- and Schwartz 1988), 37 (Margulis 1992), or as
tion and endangered species. The total many as 45 phyla (Corliss 1984). This
number of species of living organisms is extremely heterogeneous group is so diverse
thought to lie somewhere in the range of 5-30 that one author proposed 20 separate kingdoms
million (Wilson 1988; Groombridge, 1992), to accommodate them (Leedale 1974). All are
although even the higher number is possibly aquatic, although many live internally in other
conservative (e.g., Stork, 1988). We do not organisms as symbionts, commensals or para-
know the number even to the nearest order of sites. Probably every species of multicellular
magnitude because many large groups (proto- organism has protoctist associates. The
zoans, bacteria, mites, nematodes, Fungi etc.) number of species there are is unknown hut
are extremely poorly known. Erwin (1988) estimates range from 65 000 to 260 000
suggests that there could be more than 50 (Margulis and Schwartz 1988; May 1991).
million species of insects alone whereas Stork
Most animal species are "invertebrates". This
(1988) has an upper estimate of 80 million
unfortunate term is used to cover about eight
species. On Wilson's estimates of species
major phyla, a number of minor phyla and
numbers, only about 42 000 (0.14-0.84%) are
some of the phylum Chordata which includes
vertebrates.
the vertebrates. Most named taxa are insects
Why is it then, when most of us think of with about 800 000 described species with
"animals" or "biodiversity", we think of verte- estimates of several million to tens of millions
brate examples. This preoccupation with mega- remaining to be described (May 1988; Erwin
fauna is not just a problem with the general 1988, 1991; Stork 1988; Groombridge, 1992).
public - many zoologists and conservationists Other groups may be much larger than
also appear to think this way. There is a similar generally recognized. For example the Molluscs,
perception that "plants" comprise angiosperms, for which Wilson (1988) and Barnes (1989) give
gyms-osperms and ferns, because they are the a figure of 50 000 living species, which was
most conspicuous. Nevertheless other plants presumably based on the flawed estimate by
and plant-like groups (including fungi, algae, Boss (1971), actually comprises about 80 000
mosses, lichens) are also ecologically and named and probably 200 000 extant species
numerically very important. (pers. data). Another often cited example are
48 Australian Zoologist, Vol 28(14)
the nematodes, of which about 15 000 are in terms of how it affects higher plants and, to
named (Groombridge 1992), but recent a lesser extent, vertebrates (e.g., Gill et al.
estimates of living species range from 12 000 1981).
to a million or more (May 1991; Ehrlich and
If we lose rainforests it is not just the trees
Wilson 1991). Despite the obvious importance
and vertebrates that are lost. Vast numbers of
of "invertebrates", much of our knowledge of
other organisms - most of them still unknown
many groups of these animals is centred on
(e.g., Richardson 1984) - are found in our
the minuscule proportion that are pest species
forests, and other terrestrial habitats (Wilson
or taxa involved in human or livestock diseases.
1988; Ehrlich and Wilson 1991; Erwin 1988,
And yet these animals are crucial in maintain-
1991; Stork 1988). Until we understand more
ing the structure and function of ecosystems
about the processes in which these organisms
(Wilson 1987, 1988).
are involved and their relationships to the
Only about 1.7 million species of living larger animals and plants in the community we
organisms are actually named (Groombridge cannot say that we understand these systems.
1992), and of these vertebrates comprise 2.7 Most organisms, and most of the fundamentally
per cent of the total. The majority (>95%) of important ones (as discussed above), are very
the vertebrate fauna has been named, compared small - many microscopic. They are the
with only 3-20 per cent of invertebrates, in foundation of most communities but are
part a reflection of the relatively much greater largely ignored by taxonomic, ecological and
effort (and resources) expended on vertebrate conservation programmes. For example, in a
work. Of the systematists in the USA, 33 per recent work entitled "Conservation of Aust-
cent work on vertebrates, 28 per cent are ralia's forest fauna" (Lunney 1991) only one of
botanists and the remaining 39 per cent work 34 chapters dealt with invertebrates. Conserva-
on invertebrates (Barrowclough 1992). tion organizations are similarly biased. For
example, of the IUCN Species Survival Com-
The smaller, largely microscopic inverte-
mission Specialist Groups (IUCN 1990), only
brates are the most poorly known. In a study
five of 82 (6%) deal with invertebrates. Of
on "selected soil invertebrates (arthropods
these, 58 (71%) deal with vertebrates, 56 per
only) in jarrah forests in south Western Aust-
cent with mammals and birds!
ralia, 290 species were listed (about one third
of which were mites) and only 6 per cent Recorded extinctions are also heavily biased
identified to species (Postle et al. 1991). Clear- towards the mega-biota. Despite this, of
ing of native vegetation for farming results in animals, there are more molluscs recorded as
loss of some of the soil fauna (Abbott et al. having become extinct than any other group
1979; Greenslade and Greenslade 1983) and [I91 species, compared with 115 species of
the consequent deterioration of the soil (Parker birds and 58 mammals (Groombridge 1992)l.
1989). The data for molluscs are better than most
other invertebrate groups because terrestrial
In plants, too, the real diversity is not
and freshwater molluscs are relatively well
reflected in the numbers actually described.
There are about 220 500 described flowering known. They can also occupy very limited
ranges, sometimes being confined to single
plants and gymnosperms compared with only
about 101 000 species of the other plant and valleys, small islands, or a single river or spring
(e.g., Solem 1988, 1990; Ponder and Clark
"plant-like" groups (algae, fungi, ferns etc.)
1990) making them very vulnerable and yet
(Wilson 1988), although one estimate suggests
they barely rate a mention on the conservation
that there are about 1.6 million species in the
agenda.
Kingdom Fungi alone (Hawksworth 1991) with,
perhaps, 200 000 species in Australia, 80 per
One of the greatest challenges for the 90s is
cent of which are unnamed (Walker 1992).
the need to reassess our priorities. The mega-
Clearly there has been relatively much more biota bias in the study of life on earth has
taxonomic work on vertebrates and higher dominated biology to the present day. It must
plants than other life forms and this mega- change to allow a much sharper focus on the
biota bias is also reflected in most other areas major diversity of life. There have been some
of biological research. For example there are moves in this direction. For example a work-
only a few studies (Campbell and Tanton 1981; shop (Majer 1987) was held on "the role of
Majer 1984, and references therein) on the invertebrates in conservation and biological
impact of fire on litter and soil organisms survey" and, more recently, Australian National
involved in the crucial processes of litter break- Parks have contracted a report on invertebrate
down and recycling, and soil formation. Instead conservation (see Yen and Butcher, 1992). In
the impact of fire is largely being looked at addition some papers in the Conservation
December 1992
Biology in Australia and Oceania at the Uni- justify politically. But what are the costs if we
versity of Queensland in 1991 dealt with continue to largely ignore the other 99 per cent
invertebrates and a symposium on invertebrate of life on earth?
biodiversity will be held this year in Brisbane.
ACKNOWLEDGEMENTS
Yes, we should be concerned about koalas
but our concerns should be put in perspective. I thank Dan Lunney for the invitation to
It is ironic that we are primarily concerned put this viewpoint. Alan Jones, George Wilson,
with conserving Homo sapiens itself - by far Phil Colman, Wolfgang Zeidler, Ian Loch,
the single most destructive biological agent on Alison Miller and a referee made useful
the planet. Perhaps we wish to ease our collective comment and suggestions.
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