Picture the Earth as a spaceship flying through space.
It is dependent on no one except the sun which provides energy to run this spaceship.
Like a submarine, the Earth is a closed system of living and nonliving
things and is operated by life support systems. It is completely
dependent on itself to function properly. On spaceship Earth,
the life support systems are life itself. Living organisms interact
to produce processes that support life, such as oxygen production, cleansing
the air, adjusting gas concentrations, transferring energy, and recycling
waste products. Therefore, the greater the biodiversity on our planet the more options exist for possible life support systems
and backup systems should the current life support systems fail.
"Extinction is the ultimate fate of all lineages, yet we surely cannot
argue that all species are therefore badly designed or poorly adapted.
Extinction is no shame. . . . . . .
If most extinctions were the direct result of competition with superior
species, or even if most represented an inevitable failure to meet the
challenges of minor environmental change, then a stigma might be attached
to disappearance. But many, if not most, extinctions are reactions
to environmental challenges so severe and unpredictable that we have no
right to expect a successful response and, therefore, no reason to 'blame'
a species for its disappearance. . . . . . . Will blue whales be
any less exquisite in design if rapacious humanity does that last one in?
Some insurance policies offer no protection against cataclysms so momentous
and unexpected that legal language calls them 'acts of God.' Species
often die for reasons equally beyond control or calculation."
Dr. Stephen Jay Gould (1983) |
It has taken billions of years of change and fine-tuning
to weave these webs of life that keep all life forms alive. It has
taken only a fraction of that time for humans to begin unraveling these
webs through the extinction of the web’s organisms, mostly through habitat
destruction. Extinction, however, is a natural process and can occur
in several ways - including human behavior:
Background extinction: The continuous, low-level extinction of species since life has been
on Earth.
Mass extinction: The infrequent extinction of many species over a short period of geological
time.
Although extinction is a natural biological process, it
can be accelerated greatly by human activities. So what is the problem
with that? What is the difference between humans making species go
extinct versus the natural process of extinction? Two main factors
are important here. First, it is the rate at which we produce extinctions
that is considered unnatural. Usually, as one species is naturally
evolving out of existence another species is evolving as a replacement for that particular niche. Humans cause extinctions so quickly that
nature does not have time to evolve something new to fill in the
gap. Therefore, humans cause many gaps to occur in ecosystems which
hamper the functioning of biological processes that keep us all alive.
This is why biological diversity is so important. Diversity can buy
time so that a replacement species can be evolved. Thus, it acts like
a buffer so that the ecosystem does not respond to the gaps by immediately
collapsing. If that occurred, the life support systems would quickly
shut down and all of life would die. Instead, we have warning signs
that our environment is in trouble, i.e., pollution, ozone depletion, global
warming, decreasing biological diversity, etc.
Second, when it comes to human activity, not just
anything goes extinct. Our behavior is selecting out for many more
plant species than nature would. Since plants are the basis of virtually
all the food webs in the world, all life forms are currently at risk.
As we begin a new millennium, as many as one quarter of all the known plant
species on Earth have now gone extinct, mostly from human caused habitat
destruction. According to the World Wide Fund for Nature (2000):
1. The human race is operating 30% above
what the Earth can provide without suffering serious damage.
2. The results of over-stretching the Earth’s
resources have been deforestation, declining fish stocks and climate change.
3. Wildlife populations in the world’s forest,
freshwater and marine environments have declined by one third over the
last 30 years.
Currently, human caused extinctions are decreasing the
Earth’s biological diversity at an unprecedented rate (Raven & Berg
2001). Conservation biologists estimate that species are presently
becoming extinct at a rate at least 100 times the natural rate of background
extinction. More than 31,000 plant and animal species are currently
threatened with extinction. The Earth has never seen anything like
this before. It is like living on a submarine and each day all the
crew members take a whack at the air supply system with an axe. Eventually,
as the pipes, filters and pumps become increasingly damaged, the air supply
to all the crew members will dwindle and all will die. Our spaceship cannot dock anywhere for repairs. We are on our own.
References
Gould, S. J. 1983. Hen’s teeth and horse’s
toes, further reflections in natural history. New York:
W. W. Norton & Company.
Raven, P. H. & Berg, L. R.. 2001. Environment:
Third Edition. Orlando, FL: Harcourt College Publishers.
World Wide Fund for Nature. 2000. http://dailynews.yahoo.com/h/nm/20001020/sc/environment
_wwf_dc_1.html.
