Biodiversity Loss

Image credit (above): http://echeng.com/journal/images/misc/echeng-jellyfish-lake-palau.jpg

 

It is often claimed that biodiversity loss is a natural trend, occuring throughout the history of life on Earth. While it is true that there is a constant level of background species extinction with periodic natural mass extinctions, the current rate of extinction is 1,000x the natural rate. This is the largest extinction in the history of the Earth, and is also occuring much faster and is the only extinction induced by human activity. This is exhibited by the graph at left.


The graph to the left displays the four natural mass extinctions throughout history. Scientists have concluded that previous mass extinctions could have been due to episodes of ionizing radiation throughout the galaxy.  The current rate of extinction is unprecedented, and is the only one induced by human activity.


Typically, background extinctions are balanced out by the replacement of species through the process of speciation. Speciation is a progression whereby over time one species evolves into a different species (known as anagenesis) or one species diverges and develops into two or more species (also known as cladogenesis). 

 

The total number of animal species officially listed as endangered has grown from 5,205 species in 1996 to 5,435 species over a six year period. The total number of officially listed endangered animals and plants stands at 11,046. Additionally, some 3,000 whole bush land ecosystems in Australia are disappearing, taking more than 1,500 species with them.

Currently, 2/3 of bird species are declining, 1 in 8 plant species are endangered or threatened. 1/4 of mammals, 1/4 of amphibians, and 1/5 of reptiles are endangered. If this trend continues, 1/2 of all species on the planet will disappear in the next century.

The current amphibian extinction rate ranges from 25,039-45,474 times the background extinction rate for amphibians. More than half of the world's estimated 10 million species of plants, animals and insects live in the tropical rainforests. Additionally, one and one-half acres of rainforest are lost every second. One hectare (2.47 acres) may contain over 750 types of trees and 1500 species of higher plants.

Over-consumption of resources is also a large contributing factor to biodiversity loss. It forces the conversion of forests and wildlife habitat into agricultural land. Waste from this process pollutes and infects the surrounding habitats, greatly reducing genetic diversity and sometimes completely eliminating species. This, coupled with population growth, drains the ability for ecosystems and their resources to regenerate.

 

Image credit (above): http://www.nature.com/nature/journal/v405/n6783/full/405254c0.html

A graph analyzing biodiversity hot spots - places with the most biodiversity on earth. The Amazon Rainforest in Brazil is a region with one of the highest densities of biodiversity, and also holds one-fifth of the world's fresh water in the Amazon Basin

 

df

http://www.brazadv.com/images/biodiversity.bmp

Increasing demands of globalization and consumption have made a significant impact on biodiversity loss. Areas of high resource extraction are often the regions with the highest species density.  India is home to around 46,000 different species of plants alone, and has as many as 81,000 different species of animals, which accounts for approximately 8% of the world’s biodiversity. Brazil, whose Amazon region is subject to extreme deforestation, is home to 55,000 species of flora, accounting for 22% of the earth’s total.  This destructive activity in such high density areas plays a large role in our current rate of extinction.

Various approaches have emphasized the protection for keystone species (organisms with exceptional effects on their environment, proportional to their biomass), endangered species, and areas known as biodiversity hot spots. These regions have especially high densities of biodiversity. The dangers of attempting to set priorities for preservation efforts are due to our ignorance of the value any particular species provides to the web of life, or the options value it might provide in a rapidly changing global environment.

Several studies have been conducted to theoretically and quantitatively measure just how heavily economic activity has impacted our earth’s ecosystems.

Sources

Shah, Anup. "Loss of Biodiversity and Extinctions." GlobalIssues.org. <http://www.globalissues.org/article/171/loss-of-biodiversity-and-extinctions#LongTermCosts>

Turner, R. Kerry. "The Place of Economic Values in Environmental Valuation." Valuing Environmental Preferences. Nov 2001, pp.17-42.

"What is Biodiversity?" California Biodiversity Council. 2008. <http://biodiversity.ca.gov/Biodiversity/biodiv_definition.html>

Worm, Boris. "Impacts of Biodiversity Loss on Ocean Ecosytems Services." Science. 3 November 2006. <http://www.sciencemag.org/cgi/content/full/314/5800/787>