Nature published an article this week with some nice infographics that illustrate the astonishing number of species considered threatened by the International Union for Conservation of Nature, which is pretty depressing, at least if you look at the vertebrates. In what was a nice surprise, they actually included data on insects in addition to the fuzzy wuzzy taxa, noting that there are currently 993 species of insects considered threatened by the IUCN.
993 species is quite a lot, right? I mean, mammals have 1,199 threatened species, and birds 1,373, so you’d be forgiven for thinking that insect conservation is actually not too far behind the curve. But what happens when you dig a little deeper into that data?
If I were to ask you what you thought the order of insects is with the highest number of IUCN listed species, I’d be willing to bet you’d guess moths and butterflies (Lepidoptera), or possibly beetles (Coleoptera). I know that’s what I assumed. I’ve prepared a few interactive graphs of my own to help break down what those 993 species are, and how they fit into the larger picture of insect diversity (hover over wedges to see percentages, and over taxon labels to find some of the smaller wedges). And surprise, it’s probably not what you were expecting.
That’s right, dragonflies, damselflies (the Odonata), grasshoppers, katydids, and crickets (the Orthoptera) together make up more than 50% of the 993 threatened insect species. Surprised?
Next, let’s examine the total number of species that have been assessed by the IUCN, which includes the 993 species listed as threatened, plus extinct species, species considered not at risk, and species where there is insufficient data to make any conclusions.
Somewhat unbelievably, 53% of all insects assessed by the IUCN belong to the Odonata. 53%. Talk about a massive skew in the data. For context, compare the IUCN’s assessment numbers to the total known diversity for each insect order.
Look at the relative sizes of the blue Odonata wedge and the red Orthoptera wedge across all three graphs: when we look across everything we know about insect diversity, 50% of IUCN threatened insects species belong to just two orders of insects, which together make up only 2.5% of the total insect diversity. Incredibly, nearly half of all known Odonata have been assessed by the IUCN. Compare that to some of the major orders (major both in the sense of diversity and ecological/economic impact), like flies (Diptera) where 8 (the Where’s Waldo slice of pie near the top of the Assessed Graph) out of the 150,000 160,000 species we have names for have been formally assessed.
8 species of flies.
Out of 150,000 160,000.
Wow.
What’s more, some other insect orders which you would think would be correlated to the high assessment numbers of mammals and birds, specifically their ectoparasitic lice (Pthithiraptera, here included in the Psocodea) and fleas (Siphonaptera), have been completely neglected, with only 1 louse and 0 flea species assessed. Granted not all ectoparasites have high host specificity (case in point, the Passenger Pigeon louse), but when you realize that conservationists working to save charismatic species like condors and black-footed ferrets have likely caused the extinction of their respective lice (none of which are included in the IUCN Red List by the way), and add in the fact that we’ve only described a tiny fraction of the total diversity of insects, we need to assume that the conservation status of insects is being dramatically, drastically, underestimated.
It certainly seems like conservation biologists have been preferentially looking at the bigger insects (Odonata, Orthoptera and Lepidoptera make up 75% of assessed species), and pretty much ignoring the rest. It’s hard to argue with that strategy considering how difficult it is to find, identify, and track smaller insects like beetles, flies and bugs, but if we want to give a proper status report on the state of global biodiversity, we have a lot of work left to do, and any interpretations involving insect diversity need to be taken with a goliath beetle-sized grain of salt.
And no, the goliath beetle, one of the largest insects alive today, hasn’t been assessed by the IUCN either. Go figure.
Thanks for the great break-down of the data and focusing on insects. By the way, there are 160,000 Diptera species known by now (see ).
We’re guilty of assessment bias in Ontario. Of the 17 insects listed on Ontario’s Species at Risk list:
-8 Lepidoptera (6 butterflies vs 2 moths)
-5 Odonata (5 dragonflies vs 0 damselflies)
-3 Coleoptera
-1 bee
Not the same bias as IUCN (e.g., no orthopterans), but a clear bias toward charismatic insects (butterflies & dragonflies). While beetles dominate global insect diversity, flies reign supreme in Canada (I got this from Terry Wheeler’s website – if you have a citation for Cdn insect sp diversity please let me know). Yet no flies are listed in Ontario. Like you, I suspect this reflects sampling bias and how much people care about species more than their actual conservation status. I’m optimistic that things will change for the better. People care about bees and pollinators far more now than they did even ten years ago. Our challenge is to bridge people’s affection for purdy insects (I’m lookin at you, Monarch) to care for all nature. I’m working on it.
Thank you for this excellent breakdown, Morgan.
Something you did not cover but I was more than a bit concerned about was the WWF Living Planet report of threats. The number one listed threat is hunting and fishing. This once again shows the vertebrate bias in endangered species study. Unless your interests are fish or mammals, the greatest threats to the majority of animals are habitat change, habitat loss, and climate change.
Great graphics and breakdown of the data. Thanks for this.
For a piece of good news, at least as far as assessments, the General Status program in Canada has been systematically reviewing the status of many arthropod groups using NatureServe methodology (http://www.natureserve.org/biodiversity-science/publications/natureserve-conservation-status-assessments-factors-evaluating). It uses similar criteria as IUCN, but the weightings and application are a bit different and enables at least preliminary assessments of many of these “lesser known” groups. As we speak, there are the assessments of approximately 3600 beetles, 188 mosquitoes, 117 ants, 431 bees and yes–the odonates and grasshoppers of BC are waiting for me to review! Last month I waded through spider, Tricohptera, Plecoptera, Mecoptera and Ephemeroptora assessments. The groups that will have more accurate assessments (generally) are those that have had one or a few individuals that have been really keen to document what is out there.
Many will come out “unknown”and many will have a range rank (meaning that it could fall within a number of categories), but it is a start and it does mean that there are lists of species present within a jurisdiction compiled and that some of these species or guilds may get on the radar.
One thing that this has confirmed for me is that I could become (or already have…) absolutely fanatical about all collections being digitized and available for all. Having that information at hand for this type of work is critical. And that collecting and inventory programs continue, but I do realize that I am preaching to the choir on those subjects here!
Prior to the General Status assessments, I stand guilty of spending more time assessing the mega-charismatic invertebrates. In order to provide a credible assessment, good data helps! Here in BC there have been many focused detailed dragonfly and damselfly surveys, plus some hard-core keeners over the years. I probably have more confidence in the resulting Conservation Status Ranks for this group than I do for many of the small mammals! Biases do come from practicality in many cases.
Cheers -and thanks again for doing this analysis.
Leah Ramsay
Program Zoologist
BC Conservation Data Centre
Make that 188 mosquitoes, horse flies and black flies. Trust me to mistake like that on a Dipterist’s blog!
Leah
Great data breakdown. It seems to me that a lot of the troubles stem from the IUCN requirements for red-listing, which appear to be based on the way bird and mammal ecologists work. Population trends require intensive monitoring, and most people who know how to recognize the biodiversity are too busy documenting that it is there to be able to monitor it simultaneously. Insects can realistically only be assessed indirectly, by combining data on geographical occurence, number of localities, inferred habitat specificity etc. Perhaps there ought to be separate criteria for red-listing for different taxonomic groups?
In Norway, we still have a species-level red-list; but recently there has also been made a red-list for habitats. This addresses directly what supposedly is the main cause of extinction in insects, namely habitat loss, and I think it is likely to be a more efficient approach for conservation. The trouble then becomes identifying distinct and unique habitat types, and ways of recognizing them…