Biodiversity loss and Conservation : Causes of Extinction


Biodiversity loss and Conservation

Life, growth & death are the most common phenomenons of any living organisms. Extinction is the ultimate fate of all species. Species leave population in large numbers and in many forms in this universe before getting extinct. In this way species diversity increases via environmental, hereditary & cytogenetical dynamism. As a Result, new spp. are created & in other way some existing spp. are getting  extinct simultaneously. Extinction occurs over geological era of huge dimension and it is not possible to feel or recognize it over the life span of a single human being (~ 100 yrs). Some estimation on total spp. may be available, but how many lives have so far evolved on earth & how many got extinct are not yet exactly known

  • recording in realistic sense started approximately just after 1600 AD

Prediction persists that there are still 1.5 million spp. left to be discovered & named. Many spp. got extinct before we got to know 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

So far it is known that 300,000 fossil spp. have been  named and described. It is assumed that  99%  of total spp. have already been destroyed since the earth was 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.

  • 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 can be of two types-

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, 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 the body vigor, lesser the chances of survival. As a result, top consumers have more possibility of getting extinct.
  • Ability – rare spp. have less ability to colonize. which is why they are vulnerable for extinction.
  • Environmental Factors – fluctuation in climatic factor such as food supply can threaten any species.
  • Environmental Pressure – smaller population may face genetic failure or genetic variability may decrease. Offspring become more homozygous as a result their resistant capability drops & they slowly become unable to sustain.
  • Calamities – Volcanic eruption, 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 are being destroyed at a rate of 50 acre/min. so far, 40% has already been destroyed. Agricultural land accretion & human settlement caused the filling of most wetlands
  • Exploitation: Too much extraction of forest resources & wild-lives.
  • Overgrazing: which is done By farms & wild animals.
  • Damage to pollinators: Birds, insects being destroyed by traps, poisons etc. resulting in nonviable seeds.
  • Pollution: Via organisations, Industries, elements, metals, isotopes etc.
  • Mining activities: Which can destroy habitats & species directly.

Anthropogenic Pressure on Biodiversity

This is directly proportional to population increase, world population gets doubled in every 30 years. in Bangladesh, population in 1950 was 50 million and now it is more than 160 million. So all amenities (settlement, urbanization, industrialization.) of human life has increased by same magnitude & are 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 around 50% spp. loss. in the next 20 years, 2-25% spp. loss will occur. In the next 25 years, 1-10% spp. will be lost because of forest area destruction.
  • Estimated 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. This number increased by 30% ,threatened plants are now 163 spp. An assumption can be made that in the next 200-300 years around ½ of total birds & mammals will be extinct. ½ of total plant spp. might get lost in next  3000 yrs.

References & Other Links

(This article is completely based on lecture by Dr. Mohammad Azmal Hossain Bhuiyan, Professor, Department of Botany, University of Dhaka.

Some info have been added by the author, any mistake, error, misinformation and other related things found in this article are only author’s to blame)

Written by

Syed Nasif Elias Faruqui, B.S. (Hons), Department of Botany, University of Dhaka

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