Biodiversity and Conservation 2 Flashcards
Species of the IUCN Red list
IUCN- internation union for conservation of nature.
The IUCN Red
List (2004) documents the extinction of 784 species (including 338
vertebrates, 359 invertebrates and 87 plants) in the last 500 years. Some
examples of recent extinctions include the dodo (Mauritius), quagga
(Africa), thylacine (Australia), Steller’s Sea Cow (Russia) and three
subspecies (Bali, Javan, Caspian) of tiger. The last twenty years alone
have witnessed the disappearance of 27 species.
which groups are more vulnerable to extinction
some groups like
amphibians appear to be more vulnerable to extinction. Adding to the
grim scenario of extinctions is the fact that more than 15,500 species
world-wide are facing the threat of extinction. Presently, 12 per cent of
all bird species, 23 per cent of all mammal species, 32 per cent of all
amphibian species and 31per cent of all gymnosperm species in the world
face the threat of extinction.
ii) How is the ‘Sixth Extinction’ presently in progress different
from the previous episodes?
i) During the long period (> 3 billion years) since the origin and diversification of life on earth there were five episodes of mass extinction
of species.
ii) The difference is in the rates; the current
species extinction rates are estimated to be 100 to 1,000 times faster than in the pre-human times and our activities are responsible for the
faster rates.
iii) Ecologists warn that if the present trends continue,
nearly half of all the species on earth might be wiped out within the next
100 years.
how does loss in biodiversity affect a community?
In general, loss of biodiversity in a region may lead to
(a) decline in plant production,
(b) lowered resistance to environmental perturbations such as drought and
(c) increased variability in certain ecosystem processes such as plant productivity, water use, and pest and disease cycles.
Causes of biodiversity losses:
The accelerated rates of species
extinctions that the world is facing now are largely due to human
activities. There are four major causes (‘ The Evil Quartet’ is the sobriquet
used to describe them).
Habitat loss and fragmentation:
- This is the most important
cause driving animals and plants to extinction.
-The most dramatic examples of habitat loss come from tropical rain forests. Once
covering more than 14 per cent of the earth’s land surface, these rain forests now cover no more than 6 per cent.
- The Amazon rain forest (it is so huge that it is called the ‘lungs of the planet’) harbouring probably millions of species is being cut and cleared for cultivating soya beans or for conversion to grasslands for raising
beef cattle. - Besides total loss, the degradation of many habitats by pollution also threatens the survival of many species.
-When large habitats are broken up into small fragments due to various human
activities, mammals and birds requiring large territories and certain animals with migratory habits are badly affected, leading to
population declines.
Over-exploitation
- Humans have always depended on nature for
food and shelter, but when ‘need’ turns to ‘greed’, it leads to over -exploitation of natural resources. - Many species extinctions in the last 500 years (Steller’s sea cow, passenger pigeon) were due
to overexploitation by humans. - Presently many marine fish populations around the world are over harvested, endangering the
continued existence of some commercially important species
Alien species invasions:
- When alien species are introduced
unintentionally or deliberately for whatever purpose, some of them turn invasive, and cause decline or extinction of indigenous species. - The Nile perch introduced into Lake Victoria in east Africa led eventually to the extinction of an ecologically unique assemblage of more than 200 species of cichlid fish in the lake.
- environmental damage caused and threat posed to our native species by invasive weed species like carrot grass (Parthenium hysterophorus), Lantana and water hyacinth (Eicchornia crassipes).
-The recent illegal introduction of the African catfish Clarias gariepinus for aquaculture purposes is posing a threat to the indigenous catfishes in our rivers
Co-extinctions
- When a species becomes extinct, the plant and
animal species associated with it in an obligatory way also become extinct.
-When a host fish species becomes extinct, its unique assemblage of parasites also meets the same fate.
-Another example
is the case of a coevolved plant-pollinator mutualism where
extinction of one invariably leads to the extinction of the other.
Why should we conserve biodiversity: narrowly utilitarian
- The narrowly utilitarian arguments for conserving biodiversity are obvious; humans derive countless direct economic benefits from nature-food (cereals, pulses, fruits), firewood, fibre, construction material,
industrial products (tannins, lubricants, dyes, resins, perfumes ) and products of medicinal importance. - More than 25 per cent of the drugs
currently sold in the market worldwide are derived from plants and 25,000
species of plants contribute to the traditional medicines used by native
peoples around the world. - With increasing resources put into ‘bioprospecting’ (exploring molecular,
genetic and species-level diversity for products of economic importance),
nations endowed with rich biodiversity can expect to reap enormous
benefits.
define bio prospecting
exploring molecular,
genetic and species-level diversity for products of economic importance
Why should we conserve biodiversity: broadly utilitarian
- The broadly utilitarian argument says that biodiversity plays a major role in many ecosystem services that nature provides.
- The fast dwindling Amazon forest is estimated to produce, through photosynthesis, 20 per cent of the total oxygen in the earth’s atmosphere
- Pollination (without which plants cannot give
us fruits or seeds) is another service, ecosystems provide through pollinators layer – bees, bumblebees, birds and bats. - There are other intangible benefits – that we derive from nature–the aesthetic pleasures of walking through thick woods, watching
spring flowers in full bloom or waking up to a bulbul’s song in the
morning. - We cannot put a price tag on all the services provided to us by nature
Why should we conserve biodiversity: ethical argument
- The ethical argument for conserving biodiversity relates to what we owe to millions of plant, animal and microbe species with whom we share
this planet. - Philosophically or spiritually, we need to realise that every species has an intrinsic value, even if it may not be of current or any
economic value to us. - We have a moral duty to care for their well-being and pass on our biological legacy in good order to future generations.
what is meant by in situ conservation
** When we conserve and protect the whole ecosystem, its biodiversity at all
levels is protected - we save the entire forest to save the tiger. This approach
is called in situ (on site) conservation. **
Faced with the conflict between development and conservation, many nations find it unrealistic and economically not feasible
to conserve all their biological wealth. Invariably, the number of species
waiting to be saved from extinction far exceeds the conservation resources
available. On a global basis, this problem has been addressed by eminent
conservationists.
example of in situ conservation: biodiversity hotspots
- ‘biodiversity hotspots’ regions with very high levels of species richness and high degree of endemism (that is, species confined to that region and not found anywhere else).
- Initially 25 biodiversity hotspots were
identified but subsequently nine more have been added to the list, bringing the total number of biodiversity hotspots in the world to 34. - These hotspots are also regions of accelerated habitat loss.
- Three of these hotspots – Western Ghats and Sri Lanka, Indo-Burma and Himalaya – cover our country’s exceptionally high biodiversity regions.
- Although all the biodiversity hotspots put together cover less than 2 per cent of the earth’s land area, the number of species they collectively harbour is extremely high and strict protection of these hotspots could reduce the ongoing mass extinctions by almost 30 per cent.
