Vulnerable until proven Least Concern?

The International Union for Conservation of Nature (IUCN) publishes the global Red List of Threatened Species and provides the standard framework under which species are assessed under a number of categories; extinct, critically endangered, threatened etc. The red list categories are used globally, continentally and regionally and are assessed by expert groups and updated periodically. When you read about species being declared extinct or new reports on threatened biodiversity, many of the times that will be informed by data from the IUCN Red List or reflect a change in a species’ status on the/a list.

The information in the portal is referenced in national data books, museum and aquaria displays and the effort in compiling and reviewing this critical biodiversity data represents countless hours of work by thousands of contributors globally. It’s a model of international collaboration and the resource itself contains a rich amount of referenced information on a species by species basis useful for academic scientists, on the ground biologists and science communicators.

However, progress on updating the Red List across biodiversity is incredibly slow. Both in terms of the proportion of species which have been assessed but also the ongoing process of reviewing and updating information which even, with the best will in the world, will always lag behind the current status of these species in the world. At the time of writing, the headline figures on the portal are that 37,400 species are threatened with extinction, representing 28% of assessed species. Playing around with the numbers in the database, 134425 species have currently been assessed, 18752 are currently rated as Data Deficient (i.e. there isn’t enough information to make an evidenced assessment), 69149 are Least Concern (sort of the neutral position but can include species under declines of pressures regionally but not significant enough to warrant a negative status) and the rest of assessed species fall into categories of growing severity, the lowest being Near Threatened (7889) through to Extinct and Extinct in the Wild (900 and 79 species respectively). Although the numbers of assessed species seem encouragingly high, depending on what you take as an ‘upper limit’ for species diversity, only <1-<10% of species currently have an entry. At this rate, the task of assessing every species will never be complete, let alone the work needed to constantly review and update species’ statuses.

Given what we know about the threats to biodiversity, perhaps it’s time to flip the script and change the approach to species’ conservation assessment. Given that the work will never be done at this rate, perhaps all the currently unassessed species, the vast majority of known biodiversity, should, by default be listed as vulnerable and the work of assessors should be to determine whether species are of Least Concern, Near Threatened or one of the higher categories? This may not sit right with some scientists as the blanket categorising of species without assessment is not a true reflection of evidence based assessment, however, as we’ve seen from the numbers above, adopting a neutral until otherwise determined approach isn’t going to work.

Another reason to suggest such a radical change, is because, IUCN categories don’t mean a huge amount. It represents the tip of the iceberg of aggregated biodiversity conservation information but just because a species has been assessed as Threatened, Vulnerable of Critically Endangered doesn’t automatically translate into any kind of legal protection or conservation attention. It carries a bit of weight in the information gathering exercises undertaken by conservation organisations, however, the Red List category alone is just one piece of information that feeds into this. The global status only has bearing on continental or regional assessments and conservation work if species are only geographically restricted to one region, country or body of water as species can locally be doing ‘well’ or in some instances can be problematic invasives but are at risk in native ranges. Furthermore there are a myriad of different frameworks for assessing conservation status and the IUCN category, often will have no bearing on these or synthesize with them.

For example, populations of European flat oysters or native oysters depending where you’re based, Ostrea edulis, have declined 95% in the UK since the mid nineteenth century. There are a number of great restoration projects around the UK to address the declines in these ecosystem engineering species, however, the losses have been significant and recovery is currently experimental and slow. These declines have been well known for hundreds of years and have resulted in disastrous and failed introductions of other oyster species to keep oysters on plates as well as problematic knock-ons to other organisms which rely on the water filtering, reef forming oyster beds. There are also issues with diseases and introduced diseases as well as introduced parasites and predators. Despite this extremely well characterised species loss, European flat oysters have not been assessed by the IUCN on the global red list, the UK currently doesn’t even have a red list of marine mollusca so they aren’t nationally listed, they aren’t protected by CITES, they aren’t European protected species. They do have a UK Biodiversity Action Plan (BAP) and oyster bed habitats are listed as OSPAR List of Threatened and/or Declining Species and Habitats, I think. (side grumble: UK conservation policy information generally, unlike the IUCN Red List, can be extremely hard to find and on more than one occasion key conservation legislation information can only be found on the wayback machine…). The point being that just because a well known species has experienced declines, albeit in just one part of its global range, conservation and legislation assessment is inconsistent and in this case the lack of global or national assessment (I didn’t drill down into county level red lists, if they exist) hasn’t meant that oysters haven’t received conservation action or listing elsewhere. In this case, a default status of Vulnerable would only add a bit of extra weight to ongoing politicking around oyster conservation. Surely, a default status of Vulnerable could only help not harm, the plight of the European flat oyster (possibly, there’s a lot of debate around how listing does or doesn’t affect conservation action as well as taxonomic status, with the received wisdom being that native and endemic species (not subspecies) benefit from ore conservation effort, nice paper on the topic here: The impact of taxonomic change on conservation: Does it kill, can it save, or is it just irrelevant?).

There is a real need to speed up this high level conservation assessment too. The smooth handfish made a few headlines last year (there was a lot going on) as the sort of first marine fish species to be listed as Extinct on the IUCN global Red List. Surprising perhaps given that marine fish are so often in the spotlight in discussions around climate change, pollution or biodiversity loss. However, this isn’t exactly a canary in the coal mine extinction. Smooth handfish have only ever been since once. Two hundred years ago. Phenomenal effort by conservationists has meant that there’s now a solid evidence base to suggest that they aren’t around anymore, perhaps, but how many other cryptic, rarely seen, naturally scarce, difficult to access or understudied species can wait centuries to receive an assessment? A cliché of science communication around biodiversity loss is that there are likely species which will disappear before they’ve ever been described. It’s not much consolation to be ticking species off the list hundreds of years (potentially) after they did disappear. Like the smooth handfish, many other species (tens of thousands?) have only ever been seen, collected or observed a handful of times. Can we or they really wait centuries to get around to assessing their status?

Another reason to default a Vulnerable or Threatened status to all species unless determined otherwise is because vast swathes of species are impossible to assess under the IUCN criteria and the current global red list reflects this. Not a single nematodes, one of the largest groups of animals in terms of species diversity and famously thought to be ubiquitous, has currently been assessed on the Red List. The same is true of sponges, placozoans, comb jellies, hemichordates, tardigrades, nematomorphs, loriciferans, rotifers, orthonectids, dicyemids, bryozoans, brachiopods, phoronids, the list goes on. Some of these are undoubtedly victims of the subjective preferences that exist in scientific research but for many of them, they are impossible to even assess. How do you even make a decent attempt at surveying populations of microscopic organisms? Or assess their threats? Or map their distributions? What level of abundance for organisms that occur in their millions is concerning? The same is true of organisms that live deep underground, in almost every part of the ocean, under the ice and in the atmosphere. Even parasites don’t receive their dues either. Surely if any of their hosts are listed as Critically Endangered, they should be too? Many will never get an IUCN category at any level and perhaps that fact alone means they should all start out as vulnerable just in case some eDNA development down the line might be able to help us determine if their Least Concern or some level of threatened.

Human activity is impacting almost every ecosystem on Earth and the writing has been on the wall for decades. Updating every unassessed species IUCN status to vulnerable may seem like rearranging the deck chairs on the Titanic but if that default negative category helps expediate changes in conservation policy, in protecting landscapes or ecosystems or easing the glacial bureaucratic processes that lead to regional and national legislation changes, surely, that makes more sense than chipping away or forcing experts to provide a wealth of decade long research to get a status changed, which is sometimes what’s needed before a single action or action plan is implemented.

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