Biologists contend that the answer is yes because of the economic,
medical, scientific, ecological, aesthetic, and recreational value
of all species. Some environmental scientists go further and contend
that each species has an inherent right to play its role in the ongoing
evolution of life on earth until it becomes extinct without interference
by humans.
Economical and Medical Importance of Wild Species
Some 90% of today's food crops were domesticated from wild tropical
plants. Moreover, agricultural scientists and genetic engineers need
existing wild plant species to derive today's crop strains and to
develop the new crop strains of tomorrow.
Wild plants and plants domesticated from wild species supply rubber,
oils, dyes, paper, lumber, and other useful products. Nitrogen-fixing
microbes in the soil and in the plants' root nodules supply nitrogen
to grow food crops. pollination by birds and insects is essential
to many food crops.
About 80% of the world's population relies on plants or plant extracts
for medicines. At least 405 of all pharmaceuticals owe their existence
to genetic resources of wild plants, mostly from tropical developing
countries. Plant-derived anticancer drugs save an estimated 30,000
lives per year in the United States. Over 3,000 antibiotics, including
penicillin and tetracycline, are derived from micro-organisms.
Scientific and Ecological Importance
Every species can help scientists understand how life has evolved
and functions, and how it will continue to evolve on this planet.
Wild species also provide may of the ecological services that make
up earth capital and thus are key factors in sustaining the earth's
biodiversity and ecological integrity.
They supply us (and other species) with food, recycle nutrients essential
to agriculture, and help generate and maintain soils. They also produce
oxygen and other gases in the atmosphere, absorb pollution, moderate
the earth's climate, help regulate local climates and water supplies,
reduce erosion and flooding, and store solar energy. Moreover, they
detoxify poisonous substances, break down organic wastes, control
potential crop pests and disease carriers, and make up a vast gene
pool for future evolutionary processes.
Aesthetic and Recreational Importance
Wild plants and animals are a source of beauty, wonder, joy, and
recreational pleasure for many people.
Wildlife tourism, sometimes called ecotourism, is
the fastest growing segment of the global travel industry.
Ethical Importance
Some people believe that each species has an inherent right to exist,
or to struggle to exist. This ethical stance is based on the view
that each species has intrinsic value unrelated to
its usefulness to humans.
According to this view, we have an ethical responsibility to protect
species from becoming prematurely extinct as a results of human activities.
Extinctions
Extinction is a natural process and eventually all species become
extinct. Each year, a small number of species becomes extinct naturally
at a low rate. Based mostly on fossil record, evolutionary biologists
estimate that the current average natural rate of extinction is 3
species per year if there are about 10 million species. In contrast,
mass extinction is an abrupt rise in extinction rates above the natural
level. It is a catastrophic, often global event in which large groups
of existing species (perhaps 25-70%) are wiped out. Most mass extinctions
are believed to result from one or a combination of global climate
changes that kill many species and leave behind those able to adapt
to new conditions.
Conservationists believe that we are facing a new mass extinction,
which is taking place in only a few decades, rather than over thousands
to millions of years. Such rapid extinction cannot be balanced by
speciation because it takes 2,000-100,000 generations for new species
to evolve. Fossil and other evidence related to past extinctions indicates
that it takes millions of years to recover biodiversity through adaptive
radiations. Thus repercussions for humans and other species from the
current human-caused mass extinction will affect the future course
of evolution for 5-10 million years.
There are 86 documented mammal extinctions (1.8% of the total number
of mammals) that have occurred over the past 400 years. Roughly, 23%
of these extinctions have occurred in Australia and 23% in the West
Indies. The greatest number of extinctions has been among the rodents
and bats, 46 and 13 species respectively. Over the same time period
there have been 104 documented bird extinctions (1% of the total number
of birds), 20% of which occurred in Mauritius, 18% in the United States
(mostly Hawaiian islands), and 14% in New Zealand. Other geopolitical
units with large numbers of bird extinctions are Reunion, Australia,
and French Polynesia. This list clearly demonstrates that the majority
of bird extinctions have taken place on islands.
Factors that cause species extinctions
There are many reasons why animals become extinct:
1. Habitat Destruction is one of the most obvious
forms of damage to ecosystems today. Coral reefs are subject to dynamite
fishing in some parts of the world and other marine ecosystems suffer
from substrate damage done by boat anchorages. Deforestation is a
key form of destruction brought about by logging, clearing for farming
and habitat destruction that occurs slowly, bit by bit. Singapore
in Southeast Asia has had 95% of its native lowland rainforests cleared
after extensive deforestation. As many as 26 forest bird species became
extinct between 1923-1949 and 35 forest species disappeared between
1949-1998.
2. Fragmentation is a form of habitat destruction
in that much of the original habitat gets removed or modified, leaving
patches of the remaining habitat. Even though these patches may initially
have most of the species that were once there, the diversity will
degenerate. This is usually because life cycles of plants and animals
are so disrupted that many species simply die out over time. Many
animals do not like crossing open or bare ground from one patch to
another, so they remain isolated in an island of habitat, which is
vulnerable to further damage.
3. Introduced species create major problems. This
form of destruction happens without direct human interference, once
the introduced species is released. Yet, the effects can be devastating.
Introduced species create major problems in the following ways:
They
can become predators and kill native species so quickly and thoroughly
that the native species becomes extinct.
They can breed out of control, without natural checks and balances.
In this way, the introduced species eat far more than the native vegetation
can support. Since vegetation is usually the basis for an ecosystem
food chain, if that gets destroyed, the rest of the food chain will
most likely collapse.
Introduced
species can compete for space, nutrition and mineral resources. In
severe cases, an introduced species will push out the native species
over time, resulting in significant changes in the ecosystem as a
whole. E.g. On islands in the Gulf of California, many species and
subspecies of rodents are relict species, restricted to the islands,
and are now considered extinct or verging on extinction. Five native
taxa are now considered extinct (e.g. Neotoma bunkeri). The most probable
cause for extinction was the introduction of non-native species, specifically
cats.
4. Over harvesting refers to the catching of wild
populations of animals, which are left to their own devices to recover
their numbers. In the marine environment, vast numbers of fish and
marine animals are harvested every year. Little or no effort is put
into assisting their increase after harvesting, and the populations
get smaller each year and risk extinction.
5. Local forms of pollution may be absorbed by a large healthy
ecosystem. Excessive release of chemicals over extended time periods
will poison forests and render lakes almost sterile. Liquid chemical
pollution can destroy the biological fabric of river systems. Pollution
also has a tendency to spread out ever further and find its way into
food chains
Human impacts on the environment, such as habitat loss and pollution,
do not threaten all groups of species equally. At greatest risk are
species with small population sizes, species whose populations vary
greatly and species with slow rates of population growth. More specifically,
the following groups of organisms are particularly susceptible to
extinction:
Species at higher trophic levels tend to be large,
rare animals with slow rates of population growth. They are particularly
susceptible to over-exploitation or habitat loss, e.g. thylacine (Thylacinus
cynocephalus, Tasmanian wolf).
Thylacines became extinct in Australia because of the introduction
of dingoes. When the Europeans arrived, thylacines were seen as a
direct threat to the sheep introduced to the rich grazing lands. Thylacine
habitat coincided with the best farming areas. From 1830 a bounty
was offered for the scalp of each thylacine. The thylacine was seen
as a particular threat to its wool industry. Before European arrival,
thylacines most probably hunted kangaroos and wallabies, which were
pursued relentlessly until they fell, exhausted. Sheep, introduced
by the Europeans, were much easier targets.
Local endemics; species with restricted ranges are
often threatened by habitat loss. Water development, pollution, or
habitat alteration could easily drive the species to extinction. The
extremely high rate of island species extinction further testifies
to the threat that local endemics face. E.g. The Dusky Seaside Sparrow,
Ammodramus maritimus nigrescens, became extinct in 1987. It lived
on the east coast of Florida and depended on moist cordgrass Spartina
bakerii habitat for nesting sites. The decline and disappearance of
the dusky seaside sparrow is due entirely to the loss of its habitat.
The sparrow's cordgrass habitat could only grow in a very narrow range
of moisture conditions. When one habitat area was flooded and the
other drained as a result of development, there was nowhere for the
dusky seaside sparrow to live. If the dusky seaside sparrow had not
had such specialized habitat needs, it would not have become extinct.
Species with small populations; many species at higher
trophic levels have sparsely distributed populations; habitat restriction
or fragmentation may reduce their populations to very small levels.
However, the population sizes of species at lower trophic levels may
also be extremely small in a given habitat or region.
Largest members of a guild; whether or not a species
is on the top trophic level, large species have high metabolic demands,
require large habitats, and tend to occur in low densities. Thus,
the largest species within a group of species sharing similar food
sources (a guild) tend to be a high risk of extinction. E.g. all of
the lemurs that have died out since Madagascar was colonized by human
beings were as large or larger than the surviving species.
Species with poor dispersal and colonization ability;
as with local endemics, species with narrow habitat requirements and
species that can't disperse easily to new habitats are at high risk
of extinction, even if their population is widespread. For example,
in the face of a warming climate, some of the most threatened species
will be those that can't disperse as fast as suitable habitat moves
to higher elevations and latitudes.
Species with colonial nesting habits; colonial nesting
species are particularly susceptible to over-exploitation or the loss
of breeding habitat, the vulnerability of the extinct passenger pigeon
(Ectopistes migratorius) to hunters was increased by the birds' tendency
to nest in enormous colonies. The Passenger Pigeon became extinct
in central and eastern North America by 1914.
Migratory species depend upon suitable habitat in their summer
and winter range and along the course of their migratory route.
Thus, the potential for adverse effects of habitat changes on migrant
populations is high.
Species with specialised feeding habits; these species' populations
fluctuate greatly, so they face increased threats of extinction when
their population is low. E.g. The Giant Panda only eats Bamboo. If
that food source disappears then the species will decline to extinction.
Species with little evolutionary experience with disturbances;
in regions where human beings have a longstanding presence, the species
most sensitive to human disturbance have already been lost and many
of the remaining species have adapted to the additional disturbance.
In contrast, species are extremely vulnerable where human disturbance
has no historical precedent. Thus, the loss of the passenger pigeon
was related to the introduction of a predator where none had existed
before or to the introduction of a predator with a new means of hunting
e.g. the rifle, which the prey had not previously experienced.
Behavioral patterns; if one Carolina parakeet is
shot dead the rest of the flock hover over the dead body, leaving
them vulnerable to predators. The key Deer forages for cigarette butts
along highways – it’s a “nicotine addict”,
this leaves it vulnerable to predators and the chance of being hit
by a passing car.
Solutions: Protecting
Wild Species From Depletion and Extinction
How Can We Protect Wildlife and Biodiversity?
There are three basic approaches to managing wildlife and protecting
biodiversity. The ecosystem approach aims
to preserve balanced populations of species in their native habitats,
establish legally protected wilderness ares and wildlife reserves,
and eliminate or reduce the populations of non-native species.
Biologists consider protecting ecosystems to be the best way to preserve
biological diversity and ecological integrity. The basic problem is
that fully or partially protected wildlife sanctuaries make up only
6% of the world's land area, and the human population is expected
to double in the next 40 years.
The species approach is based on protecting endangered
species by identifying them, giving them legal protection, preserving
and managing their crucial habitats, propagating them in captivity,
and reintroducing them into sustainable habitats. The wildlife
management approach manages game species for sustained yield
by using laws to regulate hunting, establish harvest quotas, developing
population management plans, and using international treaties to protect
migrating game species such as waterfowl.
