Please don’t be scared by this, it is just the journalists hyping things up again. It does not mean what it seems to mean from the headlines. Insects can’t vanish and we will continue to be able to grow our crops and do agriculture. The study itself involves a lot of extrapolation on inadequate data, not their fault, it is just that there hasn’t been that much research done on insect populations for them to draw on.

The number of studies they found, 73, is not a lot for the whole world and the studies are limited. The authors are also getting criticism on twitter by experts for the way they conducted the survey, for instance they found it with a literature search in "Web of Science" for “[insect*] AND [declin*] AND [survey]” which seems likely to bias in favour of groups that are declining as well as miss out many surveys that don’t happen to use the term “survey”.

They should have stated the limitations of the survey and they do not seem to have taken the extra care needed for a survey likely to influence public opinion and decision making. This was a traditional review, and not the carefully conducted systematic review that you get in medicine and that first began to be used in conservation in 2006. See Making literature reviews more reliable through application of lessons from systematic reviews

This is another example of hugely hyped up research with click bait headlines. Journalists do love a good “catastrophe” - this is generating terrifying headlines for the easily scared.

  • Insects are not going to vanish. That can’t happen. As some go extinct others will flourish in their place.
  • It does not mean we won’t be able to do agriculture. Only some crops depend on insects and many of those require domesticated insects like bees, and those are not going to go extinct, for the same reason that, say, sheep are never going to go extinct for as long as we want to keep them.
  • The study is preliminary, based on inadequate data. It’s not clear that worldwide insects are decreasing at all. We just don’t have enough data to know. See this map - most of the map is white
  • The two studies in Australia and China can be discounted as they are of domesticated honey bees:
  • None in Asia, only two data points in Brazil for the whole of South America, none for India, none for Russia, none in Africa except a couple in South Africa, only one in Canada, none in the Arctic or Antarctic or Siberia.
  • They didn't find any studies on "most flies, grasshoppers, crickets, katydids, cicadas, phasmids, mantids, cockroaches, termites, fleas, thrips, ants, a lot of beetle families + more" (Manu Saunders tweet)

Most of the studies are from Europe or the States and many are just for the UK which is one of the best studied. And even those studies only focus on particular groups of insects.

There could be a boom of grasshoppers or ants (say) in the UK, or even worldwide, and we just wouldn’t know because there haven’t been any comparative studies of them, as grasshoppers and ants are included in the many insects that their search didn't turn up any studies for.

The issue here is that to compare populations you need to know the figures from many years ago to compare with the present. But most parts of the world just don’t have an insect population figures from a decade ago, say, or several decades ago. So there isn’t really any way to fill those gaps, except looking forwards, to see what happens in the next decade or so. We can’t go back in time and survey insect populations in the past if nobody did it at the time. Then we also need researchers to look up the old records and then write comparison studies.

It is more important for highlighting how little we know about insect numbers.

Yet this story is just running without comment in all the top news sources. It also featured on the BBC News last night with a long segment about it in "Beyond 100 days" and interview with one of the researchers. For a study that is likely to influence decision makers and public opinion, they should have made clear how patchy the data is, and the non systematic nature of the review.

Here are some example click bait titles. CNN:

The Guardian:

Exclusive: Insects could vanish within a century at current rate of decline, says global review

The subtitle there is click bait, the study does not say that insects could vanish, not as in all insects, at least, not in the abstract. Large numbers of insects are declining or going extinct sure. However others are taking their place, as you might expect. This is from the abstract of the paper, the only part I can read:

Concurrently, the abundance of a small number of species is increasing; these are all adaptable, generalist species that are occupying the vacant niches left by the ones declining. Among aquatic insects, habitat and dietary generalists, and pollutant-tolerant species are replacing the large biodiversity losses experienced in waters within agricultural and urban settings.

Also the abstract talks about what can be done about it. The causes it lists are:

So, they are declining for different reasons, it's not one thing.

What may be a problem in the tropics is that the insects that are disappearing are adapted to a narrow range of temperatures and they don’t have enough time to adapt or to migrate. The Puerto Rico study reported a big decrease in insects. Fruit eating animals and birds though remained unchanged. And just one forest, calling for more studies. That also got dramatic headlines about collapse of insects

That is not enough by itself to generalize to other tropical forests though it may well be that it's the same for others too. Nor can it be generalized to other tropical habitats.

In colder climes the results are not what you’d expect from climate change. You would expect a warmer planet to have more rather than fewer insects. The insects are adapted to the winter / summer cycles of higher latitudes and are less likely to go extinct just because of somewhat warmer temperatures.

The abstract of the paper focuses on agricultural practices as the main thing we can do however, especially, reducing insecticide use. Also cleaning polluted waters:

A rethinking of current agricultural practices, in particular a serious reduction in pesticide usage and its substitution with more sustainable, ecologically-based practices, is urgently needed to slow or reverse current trends, allow the recovery of declining insect populations and safeguard the vital ecosystem services they provide. In addition, effective remediation technologies should be applied to clean polluted waters in both agricultural and urban environments.

The paper is behind a paywall for me so I am relying on the abstract.

IMMEDIATE REACTION FROM AN INSECT ECOLOGIST ON TWITTER

Here are some comments by Dr Manu Saunders who is an insect ecologist Manu Saunders

She put it like this on Twitter:

Here is an article by Joe Rominiecki

News reports this week about the global welfare of insects have caught the world's attention, and rightfully so. Insects and related arthropods are critical to nearly every terrestrial and freshwater ecosystem on the planet. But projections of a looming mass extinction of insects are premature at this point.

The real cause for concern should be how much, in fact, remains unknown about the impact of human activity on global arthropod species and their populations. …

On the Fat

UPDATE - MORE CRITICISM OF THIS SURVEY IN THE TWITTER DISCUSSIONS

Also they found the surveys through a search for “[insect*] AND [declin*] AND [survey]” which seems likely to bias in favour of groups that are declining.

DISCUSSION

To take some of the particular examples, the German one is for increased insecticides perhaps, and changing agricultural practice.

They don’t seem to have mentioned this one going by the map in the tweet, but there was an Australian study that found collapse of bird species due to drought caused by climate change leading to the eucalyptus forest not flowering and probably because of the knock on effects on insects

OUR INSECT POLLINATED CROPS ARE NOT AT RISK FROM INSECT DECLINE BECAUSE POLLINATING INSECTS CAN BE DOMESTICATED

The honey bee is a domesticated insect, so that’s why those two data points in Australia and China are a little odd as she remarked in her tweet. Whether we have more or fewer of them - it’s a bit like asking why you have more or fewer sheep. It depends to a large extent on human decisions, and can't go extinct. But it can be more expensive for bee keepers if they have to replace colonies because of diseases like the varoa mite. They can increase numbers of bees, or use some other domesticated insect (e.g. bumble bee).

That’s why she remarked on them being “managed colonies”.

Also, only some of our crops depend on bees but ones that require other types of insects will also be fine too no matter what. We can create conditions to promote whatever type of insect the crop needs.

In the US there are no wild honey bees, though there are bees of other species. Just about all the pollination of crops that need honey bees are done by domesticated insects there. Wild honey bees are rare in Europe. Well the domesticated and wild bee are the same species - feral bees. They do play a role here

So, when it comes to our crops we don't need to worry because we can cultivate our own insect pollinators, already do for crops pollinated by bees, for others then doing things to encourage insects in agriculture such as "Bee hotels".

WE ARE NOT HEADED FOR A WORLD WITHOUT INSECTS

The changing climate is bound to mean some places have changing insect species and there would be different solutions for different places, e.g. for the German nature reserves, being careful about insecticide use and encouraging field margins, and then as for the tropics, we might have to live with a situation where some places have fewer insects than before at least for a while until new insects adapt and colonize the forests.

It doesn't mean a world without insects.

This is the post I did for the German study

The Guardian article mentions an anecdotal story by one of the researchers that his car doesn’t have as many squashed bugs on the windscreen. However one likely explanation for this is that it's because our cars are much more aerodynamic so that a lot of the insects flow smoothly past the windows rather than bash right into them.

So - if you also notice few squashed bugs on windscreens, it doesn’t necessarily mean that you have fewer insects in your area. It needs more sophisticated study methods than that.

Also relevant to this are the stories about a sixth mass extinction. We are not in the middle of one yet, just the start. It seems that it would not go all the way to a true mass extinction anyway. Also, our world started off especially diverse because it has ecosystems in many land masses that evolved in isolation from each other. As these ecosystems collide we can expect species to go extinct even while the diversity of each individual ecosystem may actually be going up due to a mix of species from different continents. Extinctions are only one side of the story.

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