THE MOST reliable guess that scientists have ventured
about the origin of the universe is that it was the result of
a cosmic explosion that took place about 25 billion years
ago. Before the explosion, all matter in the universe is
believed to have existed as a highly condensed cosmic
egg. The so-called "big bang", say scientists, sent the
matter from the cosmic egg hurtling into the universe to
form a countless number of stars.
Several stars form a galaxy. And galaxies themselves
are clustered into groups. Our own cluster, consisting of
about 25 galaxies, is called the local group and one of its
galaxies is known as the Milky Way, which consists of
over a hundred billion stars. The sun is one of the stars
in the Milky Way and it has nine planets revolving
around it, the third of which in distance from the sun is
the earth. As far as is known, the earth is the only planet
to possess that remarkable entity called life.
The earth was born about 4.6 billion years ago. A
primitive form of life is thought to have originated on
earth through complex chemical reactions about 3 6 billion years ago. These living entities, be
dividing and changing, set off a chain of events that is
referred to as biological evolution. For nearly 3 billion of
the 3.6 billion years, life existed as microscopic blobs of
protoplasm in the ocean. But about 600 ne years ago,
these living organisms became larger and more diverse
and, in time, developed hard skeletal structures.
Major developments in this drama were the evolution
about 400 an years ago of plants and animals, which
could live on land instead of water. Insects and reptiles
arrived about 300 m years ago, birds and mammals about
200 m years ago and flowering plants about 50 m years later.
Indeed, Homo sapiens manipulated their physical
environment to the extent that for the first time a species
of living organism cut loose from the constraints of biological evolution and produced 5 billion individuals.
Unfortunately, humankind's euphoria over its mas
of the universe, its ability to increase its own life
Pyectancy and its ability to genetically engineer other
forms of life led it to neglect the state of the planet on
which it lived.
Fortunately, the same mental qualities that enabled
human beings to explore space and land on the moon,
also enable them to reflect on their past, their present
and their future. Perhaps, it is this quality that will prove
humankind's ultimate saviour.
over the past 25 years or so, there has been a rather
sudden realisation that human beings have damaged
their planet beyond recognition and perhaps beyond
repair. They have destroyed the earth's life-support systems, which evolved over billions of years, and burnt fossit fuels and decimated forests on such a large scale that temperatures on earth have increased perceptibly.
The chilling realisation that the earth cannot support
humankind's bid to grow food, provide shelter and produce consumer goods for a population whose numbers
and demands are increasing is beginning to dawn on a
reasonable number of people. Yet many are still
unaware that every day they are destroying, perhaps by
the dozens, follow living creatures, which have evolved
like them.
This magnificent range of life is known by the term
biodiversity, which has only roeently become fashionable and part of the vocabulary of politicians and administrators. But few are aware that even scientists know little about this biodiversity that human beings now want
to save.
Biodiversity - the billions of life forms that exist on earth - ranges
in size from microscopic be viruses to blue whales that are more than 30 metres long. Conserving biodiversity humankind's greatest challenge.
THE MOST reliable guess that scientists have ventured
about the origin of the universe is that it was the result of
a cosmic explosion that took place about 25 billion years
ago. Before the explosion, all matter in the universe is
believed to have existed as a highly condensed cosmic
egg. The so-called "big bang", say scientists, sent the
matter from the cosmic egg hurtling into the universe to
form a countless number of stars.
Several stars form a galaxy. And galaxies themselves
are clustered into groups. Our own cluster, consisting of
about 25 galaxies, is called the local group and one of its
galaxies is known as the Milky Way, which consists of
over a hundred billion stars. The sun is one of the stars
in the Milky Way and it has nine planets revolving
around it, the third of which in distance from the sun is
the earth. As far as is known, the earth is the only planet
to possess that remarkable entity called life.
The earth was born about 4.6 billion years ago. A
primitive form of life is thought to have originated on
earth through complex chemical reactions about 3 6 billion years ago. These living entities, be
dividing and changing, set off a chain of events that is
referred to as biological evolution. For nearly 3 billion of
the 3.6 billion years, life existed as microscopic blobs of
protoplasm in the ocean. But about 600 ne years ago,
these living organisms became larger and more diverse
and, in time, developed hard skeletal structures.
Major developments in this drama were the evolution
about 400 an years ago of plants and animals, which
could live on land instead of water. Insects and reptiles
arrived about 300 m years ago, birds and mammals about
200 m years ago and flowering plants about 50 m years later.
This gradual and relatively smooth evolution to progressively more complex forms of life received a major jolt
about 2 ra years ago with the origin of a rather special
lineage of primates referred to as the genus Homo. A single species of this line evolved about 40,000 years ago into Homo sapiens, displaying all the qualities of present-day human beings. Homo sapiens' qualities of intelligence and ability to manipulate the environment enabled the species to gain unprecedented mastery over other forms of life.
Indeed, Homo sapiens manipulated their physical
environment to the extent that for the first time a species
of living organism cut loose from the constraints of biological evolution and produced 5 billion individuals.
Unfortunately, humankind's euphoria over its mas
of the universe, its ability to increase its own life
Pyectancy and its ability to genetically engineer other
forms of life led it to neglect the state of the planet on
which it lived.
Fortunately, the same mental qualities that enabled
human beings to explore space and land on the moon,
also enable them to reflect on their past, their present
and their future. Perhaps, it is this quality that will prove
humankind's ultimate saviour.
over the past 25 years or so, there has been a rather
sudden realisation that human beings have damaged
their planet beyond recognition and perhaps beyond
repair. They have destroyed the earth's life-support systems, which evolved over billions of years, and burnt fossit fuels and decimated forests on such a large scale that temperatures on earth have increased perceptibly.
The chilling realisation that the earth cannot support
humankind's bid to grow food, provide shelter and produce consumer goods for a population whose numbers
and demands are increasing is beginning to dawn on a
reasonable number of people. Yet many are still
unaware that every day they are destroying, perhaps by
the dozens, follow living creatures, which have evolved
like them.
This magnificent range of life is known by the term
biodiversity, which has only roeently become fashionable and part of the vocabulary of politicians and administrators. But few are aware that even scientists know little about this biodiversity that human beings now want
to save.
What is biodiversity? It is commonly known that the
earth abounds in a spectacular range of living organisms.
They are customarily classified into five "kingdoms", of
which the first is protistra (bacteria and blue-green
algae); the second, monera (advanced algae); third, fungi;
fourth, plants; and the fifth, animals.
1iving organisms are found almost everywhere
from the depths of the sea to tropical rain forests and
from the polar ice-caps to hot springs. They range in size
from viruses that may be no bigger than one-millionth of
a metre to the African elephant, which call weigh upto
6.5 tonnes, and a redwood tree more than 100 metres tall.
A particularly surprising aspect of biodiversity is its
apparent "lopsidedness". Ail overwhelming proportion
of the animal biomass in tropical forests is contributed
by insects (fig 1), among them, social insects such as ants
and termites. In a Brazilian tropical fonst, for
example, it has been. estimated that the biomass of ants is
approximately four times that of all vertebrates (i.e.,
amphibians, reptiles, birds and mammals) put together.
Few realise that in tropical forest ecosystems, the role of
higher animals such as Vertebrates is "insignificant",
compared to ants and other insects.
Just how many kinds of living organisms are there on
earth? The reply would be that's unfortunately asking for
too much. Even though human beings know all about
distant galaxies and can make a reasonable guess as to
how many stars there are in the universe, revertless,
when it comes to estimating how many species there are
on earth, human beings are at a total loss.
Even if one ignores the fact that many species are
becoming extinct each day, it is not easy to record,
describe or even count the number of extant species. Life,
forms are so diverse that manv vears of specialised training are required to be able io'recognise and describe
them and even then, such training will provide knowledge of just one small group of living organisms.
Scientists have been reatiCUIOUSly riaming and describing
living organisms for about 200 years. Indian taxonomists
have so far named and described about 83,000 species
(fig 2 ), while the total for taxonomists worldwide is
about 1.8 million species (fig 3 ). From these numbers
estimates were made setting the total number of species
of living organisms in the world at between 5 million
and 10 million.
Then came a major jolt, for scientists at the Smithsonian
Institution in Washington, DC - and in particular, T L
Erwin - pointed out the insects studied were mainly
from the forest floor and the forest canopy was essentially unexplored.
The tropical forest canopy
the last biotic frontier - has
since been
carefully explored
method
by using a novo
role of higher
involving blanketing selected
trees with a fog of
insecticides
animals such as
to kill all insects and other
forms of life, To
everyonc.'s
surprise hundreds of hitherto
unknown species of insects
were discovered on the
canopies of just a few trees in
Panama.
Such richness and newness
of tropical forest canopy
arthropod farina has been confirmed by other
Scientists such as Nigel Stork of the British Museum of Natural
History. who used a similar
counting technique in
Borneo. All this supports the
theory that the number of
insect species on earth is really much larger than had
been supposed. One estimate now puts their number at
30 million for arthropods alone.
Clearly, preserving biodiversity is the biggest challenge
facing humankind. But estimating biodiversity is perhaps
the greater challenge for it would require millions of
man-days of painsiaking work by highly trained biologists. Nlere difficult, it would require foresight and imagination on the part of science administrators and the realisation that all this is a worthwhile exercise.
What is required is an urgent review by scientists and
policy-makers an the significance of the finding that
insects constitute an overwhelming proportion of animal
biomass and animal species and that the total number of
species of life forms may be in excess of 30 million.
How should the world's echicaLed, enlightened citizenry respond to these rather startling findings? Should
priorities be readjusted? Should taxonomists continue to
catalogue new species at the present slow rate or should
the 30 million arthropod species be left to their fate? Can
the costs and benefits be computed? Should efforts con-
tinue to catalogue, describe and conserve these species?
These questions are compelling and humankind will
have to address itself urgently to finding answers to
them.
Raghavendro Gadagkar is director of Centre for Ecological Sciences, Indian Institute of Science.