Topic 5 : Biodiversity loss and Conservation : Causes of Extinction


Biodiversity loss and Conservation

Life, growth & death – most common phenomenon of organisms. Extinction is the ultimate fate of all spp.

Spp. leave population in large numbers and in many forms in this universe before getting extinct.

In this way spp. diversity increases via environmental, hereditary & cytogenetical dynamisms.

So, in one way new spp. are created & in other way spp. are getting  extinct.

Extinction occurs over geological era of huge dimension; not possible to feel over life span of single human being (~ 100 yrs)

Some estimation on total spp. may be available, but how many lives have so far been  evolved on earth & how many got extinct are not yet exactly known

  • recording in realistic sense started may be just after 1600 AD

Prediction persists that still 1.5 million spp. left to be discovered & named. Many spp. got extinct before we knew them.

In the following continents loss started just after human intervention

Australia: 30 – 50 thousand years ago

America: 11-12 thousand years ago

Madagaskar: 1400 years ago

New Zealand: 1000 years ago

We know that so far  300,000 fossil spp. have been  named and described. It is assumed that  99%  of total spp. have already been destroyed since the earth is born. No complete list of these spp. are available.

latest mass extinction occurred in late K ~ 138 million years back & our recording of spp. just started 400 years back. Earths’ spp are on the verge of extinction

  • IUCN Red List,1998 reports 12.55% spp. of earth are knocking at the door of extinction
  • it means out of 2,70,000 vascular plants, 33,798 are at a risk of extinction

Since earths biodiversity faces disaster, conservation strategies are highly essential.

Causes of Extinction – There is a quick increase in biodiversity which took place just after the latest mass extinction but before getting the total survey of that increased biodiversity, extinction began and now it is increasing day by day.

Causes of biodiversity loss and extinction (A. Ecological, B. Anthropogenic)

A.Ecological Causes

  • Richness & Geographical Distribution –If spp. are distributed over wide geographical region, naturally they have more population. The spp. those who have limited distribution and population, they have more chances of getting extinct; e.g. tropical spp.
  • Patchy Distribution – small & patchy population have more chances of extinction
  • Body Vigor & Trophic state – higher body vigor, lesser chance of its survival; top consumer have more chances of getting extinct
  • Ability – rare spp. have little ability to colonize, so vulnerable for extinction
  • of Env. Factor – fluctuation in climatic factor, food supply can threaten spp.
  • Environmental Pressure – smaller population may face genetic failure and genetic variability decreases , offspring become more homozygous; resistant capability drops & unable to sustain
  • Calamities – volcanic action, earthquake, forest fire, firing (accidental, willful, etc.), hurricane, glaciation, landslide, etc.

B.Anthropogenic Causes 

habitat & pollinator destruction, exploitation, overgrazing, plant introduction without controlled use of fertilizers, pesticides, pollution etc.

  • habitat destruction: tropical rain forest destroyed @ 50 acre/min; so far 40% has gone; agricultural land accretion & human settlement caused filling of most wetlands
  • exploitation: too much extraction of forest resources, wild-lives,
  • overgrazing: by farms & wild animals
  • damage to pollinators: birds, insects destroyed by traps, poisons, etc. result unviable seeds
  • pollution: via org., in-org. elements, metals, isotopes, etc.
  • mining activities: can destroy habitats & spp. directly

Anthropogenic Pressure on Biodiversity

Directly proportional to population increase, world population gets doubled every 30 yrs. in BD, 1950 population was 50 million & now more it’s more than 160 million, so all amenities (settlement, urbanization, industrialization.) of human life has increased by same magnitude & always at a cost of Biodiversity loss

Biodiversity Loss rate Determination

  • counting lost spp. in the past, studying fossil records, etc. current extinction rate is 20 spp./200 yrs
  • 90% of habitat area destruction brings ~50% spp. loss; in the next 20 yrs, 2-25% spp. loss will happen next 25 yrs, by forest area destruction 1-10% spp. will be lost
  • Estimating rate of ‘threatened’ taxa provide useful information on rate of Biodiversity Extinction.

IUCN takes care about making Red Data List between 1986 & 1990 threatened animal spp. number increased by 30% ,threatened plants 163 spp.

assumption – next 200-300 yrs ~½ of total birds & mammals will be destroyed. ½ of total plant spp. might get lost in next  3000 yrs.


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About Syed Nasif Elias Faruqui

Syed Nasif Elias Faruqui
A biology enthusiast who is currently studying in 1st year at Department of Botany in University of Dhaka. Point of interest : Biology, Music, Cats & Memes

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