When an animal is declared extinct, several data are examined: date of the last direct observation, fine exploration of its range, opinion of local organizations… But sometimes, the animal in question is a species called “Lazare” , that is, a species declared extinct prematurely and found years later. This is the case of the ivory-billed woodpecker, a bird native to Cuba and the southern United States, declared extinct… twice! Its first extinction was announced by the International Union for Conservation of Nature (IUCN) in 1996, when it was last seen in 1944. In 2004, naturalists claim to have seen it in Arkansas (United States), but the expeditions carried out do not confirm the discovery. It’s this time Fish & Wildlife Service of the United States which confirms its disappearance in September 2021. But, a twist, the bird reappeared a few months later, on April 13, 2022, in a forest in Louisiana (United States).
This example sums up the whole puzzle represented by the “lost species” identified by researchers. Difficult to observe or attracting little interest from zoologists, some are simply too little known to be able to determine their conservation status. Carried out by German and Canadian universities, this study, published on Animal Conservation on May 16, 2022, is the first to quantify more than 500 species lost among the world’s vertebrates, unseen for 50 years or more. A figure that could be greatly underestimated, which is why Arne Mooers, the originator of the study, says that “While theoretical estimates of ongoing ‘extinction rates’ are fine, it’s best to take a close look at actual species.”
A majority of reptiles concerned
Of the 562 species identified by the study, 257 are reptiles, 137 amphibians, 130 mammals and 38 are birds. This is hardly surprising for researchers, who consider that herpetofauna (reptiles and amphibians) is much less studied by biologists than mammals or birds. On April 27, 2022, a study warned of the risk of extinction of one in five reptiles within about 15 years, this taxon being very sensitive to the consequences of climate change. Among amphibians, many anurans (family gathering frogs and toads) have not been observed for several decades, this is the case of Schneider’s banana frog (Afrixalus schneideri), who only lives in a small locality in Cameroon.
Among mammals, it is rather endemic species such as the Chinese dolphin (Vexillifer Lipotes), living exclusively in the waters of the river Yangzi Jiang in eastern China. Announced extinct in 2007, specialists have called for more caution about its status. The IUCN still considers the species critically endangered, although no Chinese dolphins have been officially sighted since the death in captivity of the last representative of the species, in 2002.
Birds are an exception.
When an animal is declared extinct, several data are examined: date of the last direct observation, fine exploration of its range, opinion of local organizations… But sometimes, the animal in question is a species called “Lazare” , that is, a species declared extinct prematurely and found years later. This is the case of the ivory-billed woodpecker, a bird native to Cuba and the southern United States, declared extinct… twice! Its first extinction was announced by the International Union for Conservation of Nature (IUCN) in 1996, when it was last seen in 1944. In 2004, naturalists claim to have seen it in Arkansas (United States), but the expeditions carried out do not confirm the discovery. It’s this time Fish & Wildlife Service of the United States which confirms its disappearance in September 2021. But, a twist, the bird reappeared a few months later, on April 13, 2022, in a forest in Louisiana (United States).
This example sums up the whole puzzle represented by the “lost species” identified by researchers. Difficult to observe or attracting little interest from zoologists, some are simply too little known to be able to determine their conservation status. Carried out by German and Canadian universities, this study, published on Animal Conservation on May 16, 2022, is the first to quantify more than 500 species lost among the world’s vertebrates, unseen for 50 years or more. A figure that could be greatly underestimated, which is why Arne Mooers, the originator of the study, says that “While theoretical estimates of ongoing ‘extinction rates’ are fine, it’s best to take a close look at actual species.”
A majority of reptiles concerned
Of the 562 species identified by the study, 257 are reptiles, 137 amphibians, 130 mammals and 38 are birds. This is hardly surprising for researchers, who consider that herpetofauna (reptiles and amphibians) is much less studied by biologists than mammals or birds. On April 27, 2022, a study warned of the risk of extinction of one in five reptiles on the six continents, this taxon being very sensitive to the consequences of climate change. Among amphibians, many anurans (family gathering frogs and toads) have not been observed for several decades, this is the case of Schneider’s banana frog (Afrixalus schneideri), who only lives in a small locality in Cameroon.
Among mammals, it is rather endemic species such as the Chinese dolphin (Vexillifer Lipotes), living exclusively in the waters of the river Yangzi Jiang in eastern China. Announced extinct in 2007, specialists have called for more caution about its status. The IUCN still considers the species critically endangered, although no Chinese dolphins have been officially sighted since the death in captivity of the last representative of the species, in 2002.
Birds are an exception. They are not only the category with the fewest lost species (38), but also the only category where there are more species confirmed extinct than lost. It’s not because birds go extinct more than others, but because they are the most followed and studied animals in the world., and whose conservation data is the most complete. There are, however, a few exceptions, such as the Cebu brown dove (Phapitreron frontalis) which has not been observed since 1982, but remains classified as critically endangered for lack of new data.
Tropical environments concentrate the most lost species
Tropical forests and ecosystems close to the equator concentrate 92% of the lost species listed in the study. Indonesia holds the sad record of 69 species lost on its territory, followed by Mexico (33 species lost) and Brazil (29 species lost). Tropical areas concentrate the highest rates of animal diversity, but are also the environments where the greatest threats of extinction weigh due to deforestation, pollution and the impact of climate change.
For example, the tropics concentrate 85% of the frogs and toads listed in the world, which explains the large number of these amphibians appearing on the lists of species lost or extinct for 50 years. In addition, dense forests or inaccessible terrain are among the most difficult to explore: this is the case of the tepuis of South America, high plateaus isolated from the surrounding ecosystem which often shelter a unique fauna in the world.
Map showing the density of the number of species lost by country (the countries whose borders are in bold are so-called “megadiverse” countries, home to great biodiversity). © Thomas E. Martin & all / Animal Conservation
Some of the countries concerned produce few studies on conservation biology and Indonesia produces only 1% of the world’s scientific literature on this aspect. “The fact that most of these extinct species are found in tropical megadiverse countries is worrisome, given that these countries are expected to experience the highest number of extinctions in the coming decades.“, explains Tom Martin, zoologist and lead author of the study.
A wave of extinction announced
In 1982, the IUCN proposed to classify “extinct” species not observed for 50 years or more, but this definition, considered too simplistic, was not adopted. The main argument being the number of cases of species rediscovered after this period of time, but also the harmful consequences of premature declarations of extinction, which harm the conservation of species. In 1994, the IUCN therefore preferred define extinction as: “When there is no reasonable doubt that the last individual of a species is dead”. This definition aimed to reduce the number of “lazarus” species, by not declaring their extinction too early. For the feasibility of the study, however, the researchers favored the old method, using the 50-year mark to estimate the current number of lost species.
But according to the researchers, the wave of extinction announced this century by biodiversity experts is likely to cause an increase in the list of lost species. Something that would exert a negative influence on conservation policies, because the presence of species lost on the lists of priority species for conservation reduces the effectiveness of actions with regard to animals that actually exist. This is the case of the four species at the top of the EDGE list of the Zoological Society of London, priority, but it is impossible to find. It should also be borne in mind that the IUCN budget being limited, it can only monitor a maximum of 138,000 species. In fact, the study insists on an underestimation of extinctions, but also specifies that the 11 to 42% of species lost “possibly extinct” arouse the hope of finding some of them.
A call to care about lost species
The team noted that of these lost species, 92% are either listed as critically endangered or unlisted by the IUCN due to insufficient data. Faced with this observation, the researchers call for the situation of these species to be clarified by reducing the “latimerian deficit”, i.e. “the number of species of which it is not known with certainty whether they exist or have disappeared“. They urge zoologists to lower this number by prioritizing research on these lost species, either by rediscovering the species or by declaring it definitively extinct.
“We advocate funding thorough and focused fieldwork to rediscover lost taxa, or to provide data demonstrating that they no longer exist, as an important priority. However, in general, the importance of fieldwork within the discipline of conservation biology is declining.“, they specify in the study. Gareth Bennett, who did much of the data combing, “hopes this simple study will help make these lost species a focus for future research.”