The Tasmanian Devil is now listed as 'endangered', mostly because of the devil facial tumour disease, which has caused a decline in the population by 60 percent in the last decade.
Credit: iStockphoto
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How do scientists decide if an animal is endangered?
Many different animal species are threatened with extinction. But how do scientists decide which species are more at risk - a frog in America or a shark off the coast of Australia?
The International Union for the Conservation of Nature saw the need for some objective criteria to measure each animal's risk of becoming extinct. Their work led to the creation of the IUCN Red List.
What is the IUCN Red List?
The IUCN Red List of Threatened Species was introduced in order to quantitatively measure if species are close to extinction. It uses research from thousands of scientists working in the field.
The IUCN uses this research to categorize each species depending on how close to extinction they are.
What different categories does the Red list use?
There are nine categories in total. These are:
- Extinct: no known individuals exist
- Extinct in the Wild: no known animals exist in the wild - they may exist in captivity
- Critically Endangered: the species faces an extreme and immediate risk of extinction
- Endangered: the species faces a very high risk of extinction in the near future
- Vulnerable: the species is threatened extinction in the medium term
- Near Threatened: the species is close to the threatened thresholds or would be threatened without ongoing specific conservation measures
- Least Concern: the species is evaluated with a low risk of extinction
- Data Deficient: no assessment because of insufficient data
- Not evaluated
How do species get on the list?
Scientists evaluate species based on criteria that indicate how well the population is doing. They look at severity of population decline, species distribution, population size, number of breeding individuals and any other scientific research that indicates how close an animal is to extinction.
So far, scientist have focussed efforts on mammals and birds. In 2008, the IUCN introduced a new measurement of trends in extinction risk that will encompass much of the world's organisms.
Working in a similar way to the Dow Jones Index, which tracks financial trends, the Sampled Red List Index will track the fate of species.
Scientists believe this index will provide a broader picture of global biodiversity and conservation efforts by including lesser studied beetles, molluscs, mushrooms and plants, along with reptiles, birds and mammals.
The full criteria can be found here.
Does the Red List work for plants as well?
Yes! In 2000, plant and animal species were compiled into one big list. With more than 44,000 species now listed, it's far too large to print. An electronic copy can be found at www.iucnredlist.org.
What makes an animal endangered?
Well, that depends on the animal. The reasons why species are under threat can vary enormously.
For example, Australia's bilby population is declining due to predation by foxes, feral cats and dingoes and habitat destruction. It is currently listed as 'vulnerable.'
On the other hand, the major reasons as to why the Tasmanian Devil is 'endangered' include devil facial tumour disease, persecution from humans, road kills and low genetic diversity within the population.
Scientists note that deforestation and urban development, along with climate change are main contributors. Animal harvesting for medicines, skins and pets also depletes animal populations.
How is the Red List used?
Objective classifications like those in the Red List can help conservation groups prioritize projects, putting their time and money where it is needed most. It's also important for policy makers, who can set up regulations to protect species from human impact.
What's new for 2008?
Each year the list is revised. The 2008 list was released early this week.
Several animal populations have declined. The Australian Sealion and Temotu Flying Fox have both become 'endangered.'
But it's not all bad news. Following reintroductions of black-footed ferrets in America, the species has shifted from 'extinct in the wild' to 'endangered'.
