Our ocean’s graceful giant, instantly recognisable by their constellation-like markings, the whale shark (Rhincodon typus), still holds many mysteries despite now being one of the most studied shark species. The whale shark is a charismatic and enchanting species, these attributes make them highly attractive for tourist interactions. Pre-pandemic nearly 1 million people a year interacted with them, bringing an estimated $140 million to local economies. (Ziegler & Dearden, 2021) Despite their importance to both local communities and marine ecosystems, the whale shark is classified as an ‘Endangered’ species by the IUCN Red List mainly due to continued overexploitation.
The IUCN Red list was established in 1964, and is a powerful tool that informs conservation policies and action. The red list provides information about population size, habitat and the ecology of a species. Once a species status is assessed, how do we ensure that conservation results are being delivered for both people and nature?
Enter, the ‘IUCN Green Status of Species’, the next phase in the evolution of redlisting (IUCN, 2022). With the Red List being the global standard for assessing species risk of extinction, species which face imminent threats of extinction spur conservation efforts. But this new tool also helps us map recovery of an endangered species. Green status species are assessed against the following criteria on their recovery (Akçakaya et al. 2018):
A species is fully recovered if it is present in all parts of its range, even those that are no longer occupied but were occupied prior to major human impacts/disruption; AND
It is viable (i.e., not threatened with extinction) in all parts of the range; AND
It is performing its ecological functions in all parts of the range.
These three factors contribute to a “Green Score” (or Species Recovery Status) ranging from 0-100%, which shows how far a species is from it’s fully recovered state (IUCN, 2022). One of the biggest strengths of the Green Status species is its potential to tell the story of a species, how its status has changed over time and how it might change in the future. The Green Status compliments the Red List, providing a more comprehensive look at a species. So, what does this mean in practice for the whale shark?
Following the above criteria, we can make a first pass at the current Green Status of whale sharks, and their long-term recovery potential. To calculate this To calculate this, Dr. Pierce from Marine Megafauna Foundation, Dr. Grace from Oxford University, and Dr. Araujo from MARECO, assessed five population groups (known as population units) from the Atlantic Ocean, Western Indian Ocean, Arabian Sea, Southeast Asia and the Eastern Pacific Ocean. Each population group was assessed individually against IUCN Red List criteria and Green Status criteria and they provisionally inferred that the whale shark's Species Recovery Status is 29% (25 - 55%) .
This means that with current and ongoing conservation management there appears to be little risk of whale sharks becoming regionally extinct in any of the individual spatial units mentioned above. It is important to note that the spatial units used for the first formal whale shark assessment may end up being different from those described here as the IUCN is in the process of formalizing an approach to spatial units.
For the moment, it is hoped that the recovery rate will reach 100% in the next 100 years. However, as the species abundance remains relatively low and has a projected slow rate of recovery owing to biological constraints, concerted long-term efforts are needed to reduce broad scale threats.
You can read more about the green status of whale sharks in Chapter 12 of Whale Sharks: Biology, Ecology and Conservation edited by Dr. Al Dove and Dr. Simon Pierce or the formal Green Status assessment on the IUCN Red List site here