A large proportion of the world’s species are threatened, and the body that keeps track of all of this, the International Union for the Conservation of Nation (IUCN), does a remarkable job of gathering a large and varied amount of information together to inform their classifications. Invariably, however, there are some species for which data is completely unavailable for a host of reasons – the cryptic nature of the species, its low population density, or even its size.

Data from the IUCN here: http://www.iucnredlist.org/about/summary-statistics#Tables_1_2
Data from the IUCN here: http://www.iucnredlist.org/about/summary-statistics#Tables_1_2

In fact, around one-sixth of all the species of living things on earth that the IUCN evaluates are classified as Data Deficient, and 10% of all mammals, birds, reptiles and amphibians together also fall under the same category. The table above indicates that this is not proportionate over the different groups, but that amphibians are largely unknown in comparison to birds, where only 1% remain unstudied.

ARKive species - Crested black macaque (Macaca nigra)

A recent study in the journal Conservation Biology attempted to use modeling to predict the conservation category (Vulnerable, Endangered, etc.) for data deficient species based on a host of other variables. When tested against species with assigned categories, the model predicted the correct category in 92% of all cases.

“Applying the best model to DD [data deficient] species, we predicted 313 of 493 DD species (64%) to be at risk of extinction, which increases the estimated proportion of threatened terrestrial mammals from 22% to 27%.”

The authors conclude that “unless directly targeted for monitoring, species classified as DD are likely to go extinct without notice” – a terrifying thought indeed.


LUCIE M. BLANDBEN COLLENC. DAVID L. ORME2 & JON BIELBY (2014). Predicting the Conservation Status of Data-Deficient Species . Conservation Biology