A new study of the world's seven sea turtle species provides evidence that their numbers are growing overall (unlike many endangered vertebrates), thanks to years of conservation efforts that have played a key role in sea turtle recovery -- even for small sea turtle populations. Sea turtles have historically suffered population declines for reasons that include accidental catch and harvesting adults and eggs.

Such decreases have motivated worldwide conservation efforts since the 1950s to employ tactics like strict fishing regulations and beach protection measures. To examine the current global status of sea turtles, Antonios Mazaris and colleagues studied 4,417 annual estimates of sea turtle nesting abundance based on specific time periods of nesting data collection that ranged in length from six to 47 years.

They used estimates from 2010 or later to evaluate the length of time periods required to detect significant trends in abundance within Regional Management Units (which represent discrete groups of nesting sites in certain areas that are distinct from one another based on genetics, distribution, movement, and demography) for each species, finding a majority of population increases (95 significant increases compared to 35 significant decreases).

Despite the encouraging upward population trends, Mazaris et al.'s results complement International Union of Conservation for Nature (IUCN) assessments of sea turtle status, which lists six sea turtle species as endangered.

The authors also found that while longer time periods of nesting data collection are important for detecting population trends, shorter intervals not currently used by IUCN could still provide important information, though they highlight the need for more updated and continuous nesting site information.