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"Some taxa and sites showed decreases in abundance and diversity while others increased or were unchanged, yielding net abundance and biodiversity trends genera

"Some taxa and sites showed decreases in abundance and diversity while others increased or were unchanged, yielding net abundance and biodiversity trends generally indistinguishable from zero. " That's very interesting, and REALLY surprising. Even the citations listed there has this one: "More than 75 percent decline over 27 years in total flying insect biomass in protected areas." Hoping to see the details on how they did things.

hinkley 6y ago
This all gets really complicated really fast. Which is not to say we shouldn't discuss it or even take preliminary actions, but it does mean the answers will evolve. One of the profound moments for me reading 1491 is the assertion that the collapse of buffalo and passenger pigeon populations was at once tragic and overblown - the absence of anthropomorphic pressure on the environment caused these populations to explode, draw more attention, and ultimately collapse through predation. Meanwhile, many of the chemicals we banned post-Silent Spring affected insects and birds. Insect numbers are affected by many ecological stressors, from range, to pollution, to predation by birds. If you kill or drive away all of the barn swallows and purple martins, you get more mosquitoes. If the barn swallows come back, you get fewer mosquitoes. If you set up martin houses, fewer mosquitoes. Fewer mosquitoes? Fewer dragonflies. All along the food chain things shift.
paulcole 6y ago
When I was a teenager, I caught a bunch of beetles and put a dot of white out on some of them. Then I went back a week later, caught a bunch of beetles again, and counted how many had white out on them. Used that to estimate the beetle population. This wasn't a school project.
- chris1993 6y ago
  You might have been inadvertantly measuring how white dots make beetles more susceptible to predation.
joshvm 6y ago
Ecology is incredibly difficult because everything is horrendously under-sampled. Essentially all ecology reduces to counting species over time and somehow extrapolating to huge areas. So-called total count surveys are extremely expensive. I can only speak from a megafauna perspective (eg not insects), but there were recently some results that suggested that animal decline in Africa was overestimated. Caused quite a stir. And it makes sense when you learn how people count animals in aerial surveys - photographic interpretation is novel because most ecologists are not used to dealing with that level of data, nor the complexity in designing the camera systems, and it was impractical to do with film in the past. The gold standard is someone with a voice recorder in a plane. When you actually go through aerial photographic surveys, you spot all sorts of things that the observers missed, because they're not superhuman. That's not to say there is no decline - poaching has still decimated populations - but for some species it might not be as bad as you think. In theory the methods (things like JOLLY2) are supposed to correct for you missing a certain percentage, and distance to the animals etc, but that relies on you knowing what those uncertainties are. I don't know how insect surveys are performed, but you have to understand that you're always trying to make sweeping assumption about "the whole of the US" based on very sparse sampling. Not to mention controlling for different environments. For example in the paper you cited, they try and control for a ton of stuff like habitat. I'm not an entomologist so I won't comment on the paper beyond that, but do be aware that "standard techniques" may well be something that we've done since the 60s and nobody questions it.
- DuskStar 6y ago
  > but that relies on you knowing what those uncertainties are. And it also relies on those uncertainties not changing. "Elephants start spending more time in the forests and not open areas to avoid poachers" would reduce counts from airplanes without changing the number of elephants, for example.
- Natsu 6y ago
  For insects, there are a lot of different traps based on the nature of the insects being sought. There's a pretty good list here: https://en.wikipedia.org/wiki/Insect_trap https://en.wikipedia.org/wiki/Insect_trap As I understand the sampling, you pretty much just put the traps out and count up how many insects you get of each type. Purely anecdotally, I feel like the number of butterflies is way down from the level you'd see during, say, the 90s. It seems like I just don't see as many different types any more and even the more common types feel vastly reduced in number. I used to see monarchs and sulfers and painted ladies and red admirals and cabbage butterflies all the time, now I barely see a few cabbage butterflies or sulfers and occasionally a painted lady or two. I never get to see the less common things like buckeyes any more, which is a pity given that they're my favorite.
brandmeyer 6y ago
> Hoping to see the details on how they did things. Me, too. You can get some inferences based on what others in the field are saying about the paper, although I have no idea how well-representative these folks are, either. https://www.sciencemediacentre.org/expert-reaction-to-study-of-insect-numbers-in-the-us/ https://www.sciencemediacentre.org/expert-reaction-to-study-... The strongest criticism centers around how well the data sets cover the US biosphere. For example, "Crossley’s datasets include aphids on farmland in the Midwest (40% of all the time series), and samples in urban habitats in Phoenix, Arizona (24% of all time series)." So it seems that which the abstract giveth, the article body taketh away.
kingkawn 6y ago
75% decline in flying insects is horrifying

hinkley 6y ago

This all gets really complicated really fast. Which is not to say we shouldn't discuss it or even take preliminary actions, but it does mean the answers will evolve. One of the profound moments for me reading 1491 is the assertion that the collapse of buffalo and passenger pigeon populations was at once tragic and overblown - the absence of anthropomorphic pressure on the environment caused these populations to explode, draw more attention, and ultimately collapse through predation. Meanwhile, many of the chemicals we banned post-Silent Spring affected insects and birds. Insect numbers are affected by many ecological stressors, from range, to pollution, to predation by birds. If you kill or drive away all of the barn swallows and purple martins, you get more mosquitoes. If the barn swallows come back, you get fewer mosquitoes. If you set up martin houses, fewer mosquitoes. Fewer mosquitoes? Fewer dragonflies. All along the food chain things shift.

paulcole 6y ago

When I was a teenager, I caught a bunch of beetles and put a dot of white out on some of them. Then I went back a week later, caught a bunch of beetles again, and counted how many had white out on them. Used that to estimate the beetle population. This wasn't a school project.

chris1993 6y ago
You might have been inadvertantly measuring how white dots make beetles more susceptible to predation.

joshvm 6y ago

Ecology is incredibly difficult because everything is horrendously under-sampled. Essentially all ecology reduces to counting species over time and somehow extrapolating to huge areas. So-called total count surveys are extremely expensive. I can only speak from a megafauna perspective (eg not insects), but there were recently some results that suggested that animal decline in Africa was overestimated. Caused quite a stir. And it makes sense when you learn how people count animals in aerial surveys - photographic interpretation is novel because most ecologists are not used to dealing with that level of data, nor the complexity in designing the camera systems, and it was impractical to do with film in the past. The gold standard is someone with a voice recorder in a plane. When you actually go through aerial photographic surveys, you spot all sorts of things that the observers missed, because they're not superhuman. That's not to say there is no decline - poaching has still decimated populations - but for some species it might not be as bad as you think. In theory the methods (things like JOLLY2) are supposed to correct for you missing a certain percentage, and distance to the animals etc, but that relies on you knowing what those uncertainties are. I don't know how insect surveys are performed, but you have to understand that you're always trying to make sweeping assumption about "the whole of the US" based on very sparse sampling. Not to mention controlling for different environments. For example in the paper you cited, they try and control for a ton of stuff like habitat. I'm not an entomologist so I won't comment on the paper beyond that, but do be aware that "standard techniques" may well be something that we've done since the 60s and nobody questions it.

DuskStar 6y ago
> but that relies on you knowing what those uncertainties are. And it also relies on those uncertainties not changing. "Elephants start spending more time in the forests and not open areas to avoid poachers" would reduce counts from airplanes without changing the number of elephants, for example.
Natsu 6y ago
For insects, there are a lot of different traps based on the nature of the insects being sought. There's a pretty good list here: https://en.wikipedia.org/wiki/Insect_trap https://en.wikipedia.org/wiki/Insect_trap As I understand the sampling, you pretty much just put the traps out and count up how many insects you get of each type. Purely anecdotally, I feel like the number of butterflies is way down from the level you'd see during, say, the 90s. It seems like I just don't see as many different types any more and even the more common types feel vastly reduced in number. I used to see monarchs and sulfers and painted ladies and red admirals and cabbage butterflies all the time, now I barely see a few cabbage butterflies or sulfers and occasionally a painted lady or two. I never get to see the less common things like buckeyes any more, which is a pity given that they're my favorite.

brandmeyer 6y ago

> Hoping to see the details on how they did things. Me, too. You can get some inferences based on what others in the field are saying about the paper, although I have no idea how well-representative these folks are, either. https://www.sciencemediacentre.org/expert-reaction-to-study-of-insect-numbers-in-the-us/ https://www.sciencemediacentre.org/expert-reaction-to-study-... The strongest criticism centers around how well the data sets cover the US biosphere. For example, "Crossley’s datasets include aphids on farmland in the Midwest (40% of all the time series), and samples in urban habitats in Phoenix, Arizona (24% of all time series)." So it seems that which the abstract giveth, the article body taketh away.

kingkawn 6y ago

75% decline in flying insects is horrifying