FAQ (Frequently Asked Questions)

This FAQ is designed to give basic answers to the most frequently asked questions about the current biodiversity crisis. If you have a question which should be addressed in this FAQ then please let me know so that I can formulate an appropriate answer. You can email me at , or alternatively, simply use the Contact Us page.

How many entries are in the REPAD database?

At present the database contains around 8,750 entries. This includes those (subspecies) which are "missing" (possibly to probably extinct) or have been rediscovered. As well as both extinct and rediscovered domestic breeds and cultivated varieties. A detailed statistical breakdown of the database will be available in the future.

How many species have recently become extinct?

That depends a lot upon what one means by 'recent'. For the purpose of accuracy REPAD construes 'recent' to mean within the last 100,000 years. This is to encompass the start of the current human-caused biodiversity crisis deep in the Pleistocene epoch. Rather than only considering species which persisted until after the rather arbitrary date of 1500 AD, as do the IUCN and many other scientists.
Unfortunately, for all but birds and herpetofauna there have been no real estimates of the number of taxa which have recently become extinct (Duncan et al. 2013; Alroy, 2015). In the case of birds1, Duncan et al. (2013) has estimated that almost 1,000 species of nonpasserine landbirds have become extinct during the Holocene on Pacific Islands; and that taking passerines and nonpasserine seabirds into account would increase this number to around 1,300. If we consider the rest of the world, then there may have been somewhere in the region of 2,000 more avian taxa some 10,000 years ago than there is today.

How fast is the current extinction rate?

Estimates of the current extinction rate vary wildly, from hundreds of species extinctions per decade to as high as 30,000 species per year (or more). Given that there are currently less than 5,000 known or suspected extinctions within the last 5,000 years across all taxonomic groups (i.e. fish, birds, mammals, plants etc.), the demonstrable extinction rate is therefore less than 1 species per year. The problem with quantifying the current extinction rate is figuring out how to take into account the many extinctions which have undoubtedly taken place but for which we have little or no evidence.
The most accurate estimate of the current number of species on Earth is 8.7 million species. But if the extinction rate were really 30,000 species per year as some suggest then we would have lost every single species on Earth within 290 years of the start of the current 'mass extinction', including ourselves. By contrast, it has now been several thousand years or more since the extinction rate has been accelerated to several orders of magnitude above the background extinction rate, and the Earth still retains most of its biodiversity. So clearly such estimates are grossly inflated.
The simple truth is that nobody knows how fast we are losing species, nor how long we have been losing them for. We can currently only calculate species losses if we have preserved material, either recent, subfossil or fossil, or some other indicator that such species existed such as oral tradition, cave paintings etc.

Is the current extinction rate slowing down?

There is a widespread public perception that the current extinction rate is slowing down thanks to conservation programs, better legal protection for endangered species, the surgence of the environmental movement, education about our natural resources, better farming practices, etc. And at least for birds, reptiles, mammals and marine species, in general this holds true. However, since the 1970's there have been three separate extinction events which have caused the current extinction rate to be accelerated to faster than it has ever been known to have been within the last 100,000 years!
I will cover this in much more detail in a future article, but the three events alluded to are: the crisis in Lake Victoria, East Africa caused by the population explosion of the introduced Nile perch (Lates niloticus) which has likely caused the extinction of c.200 endemic species of cichlid fishes (Goldschmidt, 1996); the global decline and extinction of amphibians (mainly frogs), most likely due to chytrid fungus (Stuart et al. 2004; Collins et al 2008); and the introduction of the predatory snail Euglandina rosea to the Society Islands (Coote & Loève, 2003).

What species are likely to go extinct next?

Sadly several species of animals are functionally extinct, or close to being so. Functional extinction means that although individuals of a species or subspecies still survive there are not enough of them to sustain the population and it will become extinct in the near future. Of course, as it is difficult to prove extinction new populations of some of these taxa could theoretically be discovered which would pull them back from the inevitability of extinction. However, this is unlikely in each case. For a list of animals whose current global population estimates are all less than 250 see here.
Regarding plants, population estimates for all but the very rarest species and subspecies lack relative accuracy. Unfortunately I currently do not have a list of the rarest plants in the world, but I hope to produce such a list in the near future.

What are the main causes of the current extinction crisis?

Only a handful of recent extinctions (i.e. extinctions which have taken place within the last 100,000 years) can truly be considered as 'natural'. For example, the bio-luminescent cockroach Lucihormetica luckae is believed to have gone extinct after its only known habitat, a volcanoe, erupted (Vršanský et al. 2012; but see Rudolph, 2012).
By far the main cause of extinctions within historical (and prehistoric) times has been Homo sapiens sapiens, or modern humans. Directly through hunting, trapping, poisoning and otherwise killing. And indirectly through habitat modification, introduced species, disease, climatic changes such as human-induced drought, and starvation. In most instances a single factor is not sufficient on its own to drive a species extinct. Multiple causes are normally necessary to entirely kill off a species.

Has the "sixth mass extinction" arrived?

There is no universal agreement over the definition of a "mass extinction". But palaeontologists virtually all agree that at least 50% of species must go extinct within a geologically short period of time; no more than several million years. The uncertainty over exactly how many species have existed within the recent past disallows us from definitively answering this question. But if the estimate of 8.7 million species is used, which is now the most widely accepted estimate, then a minimum of 50% of these, or 4.35 million, will need to have gone extinct within several million years. And although "only" around 2 million species have been formally described to date, the loss of biodiversity amongst larger animals, if the extinction crisis is not significantly taxonomically biased, is nowhere near that required to be able to say that we are in the midst of a sixth mass extinction, despite media reports to the contrary.

Can cloning bring back extinct species?

Technically, it already has. For a few brief minutes the Pyrenean ibex or Bucardo (Capra pyrenaica pyrenaica) was brought back to life, but died due to "physical defects in [the] lungs" (Folch et al. 2009:1026). Scientists say that they are on the verge of bringing other extinct species back to life. Apparently we are less than 5 years away from cloning the Woolly mammoth (Mammuthus primigenius), and attempts are being made to clone the Southern gastric brooding frog (Rheobatrachus silus) (Philipps, 2013). Imagine being able to see Woolly mammoths grazing the tundra. It would also be a huge tourism industry which could generate jobs for the currently unemployed. It would be like being transported back 10,000 years without the need for a time machine.
But we also need to keep in mind the failed attempts like the thylacine cloning project. To clone an individual and have it survive for a few minutes or even a lifetime is one thing. But to have a viable population requires genetic diversity, which just doesn't exist in the hypodigms of many recently extinct species. DNA is often too badly degraded in museum specimens to allow sequencing, which is a key step in cloning a species. The Woolly mammoth may be an exception to this trend, as frozen carcasses allow the preservation of partially or fully intact DNA. However, there aren't too many other species which have a real chance of being brought back to life permanently (well, until they become extinct again).

What is the aim of REPAD?

The goal is to compile all relevant data on extinct and rediscovered species and present it in a single, easily accessible, place: the internet. This will be a life long project as the completed website (if that ever eventuates) will be approximately 50-100 million words. However, I am in it for the long haul and after 5 years my enthusiasm for the subject has only grown.


1 There has been an estimate by David Steadman in a book chapter that 1,000 species of rails (family: RALLIDAE) have become extinct on Pacific islands. However, this is only from memory as my computer crashed and I lost the pdf of his book chapter, so am unable to cite it proper.


Alroy, John. (2015). Current extinction rates of reptiles and amphibians. PNAS. doi: 10.1073/pnas.1508681112 [Abstract]
Collins, James P. et al. (2008). Extinction in Our Times: Global Amphibian Decline. New York: Oxford Univesity Press. 273 pp.
Coote, Trevor and Loève, Éric. (2003). From 61 species to five: Endemic tree snails of the Society Islands fall prey to an ill-judged biological control program. Oryx 37: 91-96. [abstract]
Duncan, R. P., Boyer, A. G. and Blackburn, T. M. (2013). Magnitude and variation of prehistoric bird extinctions in the Pacific. Proc. Natl. Acad. Sci. USA 110(16): 6436-6441.
Folch, J. et al. (2009). First birth of an animal from an extinct subspecies (Capra pyrenaica pyrenaica) by cloning. Theriogenology 71(6): 1026-1034. [abstract]
Goldschmidt, Tijs. (1996). Darwin's Dreampond: Drama on Lake Victoria. Cambridge, Massachusetts: MIT Press.
Phillips, Nicky. (2013). Extinct frog hops back into the gene pool. The Sydney Morning Herald, 16 March (Saturday).
Rudolph, Michael. (2012). New species of bioluminescent cockroach possibly already extinct by volcanic eruption. Mongabay.com [Accessed 15 November 2012]
Stuart, Simon N. et al. (2004). Status and Trends of Amphibian Declines and Extinctions Worldwide. Sciencexpress, 14 October, 1-5.
Vršanský, P., Chorvát, D. A., Fritzsche, I., Hain, M. and Ševčík, R. (2012). Light-mimicking cockroaches indicate Tertiary origin of recent terrestrial luminescence. Naturwissenschaften 99(9): 739-749. [abstract]