Showing posts with label environment. Show all posts
Showing posts with label environment. Show all posts

Monday, April 27, 2009

Recently Extinct Mammalian Species

This is a short list of recently extinct mammals, their dates of extinction, and some more interesting details. Many of these animals were extinct as a result of human hunting or through the destruction of their natural environment.

Javan Tiger (ext. 1990)

The photograph of a live Javan tiger taken in 1938

The Javan tiger (Panthera tigris sondaica) was a subspeices of tiger limited to the Indonesian island of Java. As a result of hunting and habitat destruction, this subspecies was made extinct in the 1980s, but the extinction became increasingly probable from the 1950s onwards, when fewer than 25 tigers remained in the wild.

In 2008, an unidentified body of a female mountain hiker was found in Central Java, allegedly died from tiger attack. Villagers who found the body also claimed some tiger sightings in the vicinity. But until concrete evidence can be produced, the Javan tiger must be considered yet another tiger subspecies which is probably extinct.


Zanzibar Leopard (ext. 1996)

Panthera pardus adersi, Zanzibar Museum, Helle V. Goldman and Jon Winther-Hansen

The Zanzibar Leopard (Panthera pardus adersi) is an extinct subspecies of leopard endemic to Unguja Island in the Zanzibar archipelago, Tanzania. Efforts to develop a conservation programme in the mid-1990s were stopped when researchers concluded that there was little prospect for the animal's long-term survival.

Rural Zanzibaris’ descriptions of the leopard are coloured by the belief that these carnivores are kept by witches and sent by them to harm or otherwise harass villagers. After the Zanzibar Revolution, a combined anti-witchcraft and leopard-killing campaign was launched under the leadership of the famous witch-finder, Kitanzi. The result of this campaign was to bring leopards to the brink of extinction.


Pyrenean Ibex (ext. January, 2000)

Pyrenean Ibex; Image from Cabrera, A. (1914)

The Pyrenean Ibex (Capra pyrenaica pyrenaica) once ranged across the Pyrenees in Spain and France and the surrounding area, including Navarre, the Basque Country, north Aragon and north Catalonia. The last natural Pyrenean Ibex, was found dead on January 6, 2000, killed by a falling tree.

The biotechnology company Advanced Cell Technology, Inc. used nuclear transfer cloning technology to clone the Pyrenean ibex from the tissue that was taken in 1999. The first attempts to clone the species failed. In 2009, one clone was born alive, but died seven minutes later, due to physical defects in the lungs.


West African Black Rhinoceros (ext. July, 2006)

Black Rhinoceros in Ngorongoro Conservation Area, Tanzania; photo: Yoky

West African Black Rhinoceros (Diceros bicornis longipes) was once widespread in the savanna of central-west Africa but on 7 July 2006, it was (tentatively) declared extinct.

Around 1980 the population was in the hundreds. The illegal poaching contributed to the species' demise, by 2000 only an estimated 10 survived. An intensive survey of the last remaining habitat of the species in early 2006 found none. There are eight western black rhinoceros alive: six are in the Czech republic and two are in the San Diego Zoo's Wild Animal park. It might be possible to save this species with work between these two locations.

Baiji: Chinese River Dolphin (ext. December, 2006)


An illustration of the Baiji; author: Alessio Marrucci

Nicknamed "Goddess of the Yangtze", Baiji is classified by the 2007 IUCN Red List as a possibly extinct species. A late 2006 expedition by scientists from six nations failed to find any Baiji in the Yangtze river.

As China industrialized in recent decades, and used the river for transportation, hydroelectricity, and fishing the Baiji population declined drastically. The last uncontested sighting of a baiji was in 2002. This was the first recorded extinction of a well-studied cetacean species directly attributable to human influence.

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Wednesday, April 1, 2009

Exceptional Thermal Characteristics of Water


(Frozen lake on Mather Island, Antarctica; Author: Hannes Grobe, Alfred Wegener Institute)

The expansion of water with temperature is approximately linear. However, on a fine scale it is not exactly linear. In the temperature range from 0°C to 4°C water decreases in volume with increasing temperature, its coefficient of volume expansion is negative. Water also expands when it freezes, while most materials contract when they freeze. This has important consequences for plant and animal life in lakes. A lake cools at the surface, the cooler and denser water from the surface flows to the bottom. But when the air temperature drops below 4°C, the surface water is less dense than the water below, the downward flow ceases. The ice is less dense than water, and it floats. The water at the bottom always remains at 4°C unless the entire lake is frozen.

Related link: Water Structure and Science, an excellent web site on physics and chemistry of water.