Global Insect Extinction – a never ending story

I have had an unexpectedly busy couple of weeks talking about declines in insect populations.  Back in November of last year I wrote a blog about the sudden media interest in “Insect Armageddon” and followed this up with a more formal Editorial in Annals of Applied Biology at the beginning of the year (Leather, 2018).  I mused at the time if this was yet another media ‘storm in a teacup’ but it seems that the subject is still attracting attention.  I appeared on television as part of TRT World’s Roundtable programme and was quoted quite extensively in The Observer newspaper on Sunday last talking about insect declines since my student days 🙂 At the same time, as befits something that has been billed as being global, a similar story, featuring another veteran entomologist appeared in the New Zealand press.

The TV discussion was quite interesting, the panel included Nick Rau from Friends of the Earth, Lutfi Radwan, an academic turned organic farmer, Manu Saunders from Ecology is Not a Dirty Word and me.  If they had hoped for a heated argument they were out of luck, we were all pretty much in agreement; yes insects did not seem to be as abundant as they had once been, and this was almost certainly a result of anthropogenic factors, intensive agriculture, urbanisation and to a lesser extent climate change.  Unlike some commentators who firmly point the finger at the use of pesticides as the major cause of the declines reported, we were more inclined to towards the idea of habitat degradation, fragmentation and loss.  We also agreed that a big problem is a lack of connection with Nature by large sections of the population, and not just those under twenty.  We also felt very strongly that governments should be investing much more into research in this area and that we desperately need more properly replicated and designed long-term studies to monitor the undeniable changes that are occurring.  I had, in my Editorial and an earlier blog post, mentioned this point and lamented the paucity of such information, so was pleasantly surprised, to receive a couple of papers from Sebastian Schuh documenting long-term declines in Hemiptera and Orthoptera in Germany (Schuh et al., 2012ab), although of course sad, to see yet more evidence for decreasing insect populations.

The idea that insects are in terminal decline has been rumbling on for some time; more than a decade ago Kelvin Conrad and colleagues highlighted a rapid decline in moth numbers (Conrad et al., 2006) and a few years later, Dave Brooks and colleagues using data from the UK  Environmental Change Network revealed a disturbing decline in the numbers of carabid beetles across the UK (Brooks et al., 2012).   In the same year (2012) I was asked to give a talk at a conference organised by the Society of Chemical Industry. Then, as now, I felt that pesticides were not the only factor causing the biodiversity crisis, but that agricultural intensification, habitat loss and habitat degradation were and are probably more to blame.  In response to this quote in the media at the time:

“British Insects in Decline

Scientists are warning of a potential ecological disaster following the discovery that Britain has lost around 7% of its indigenous insect species in just under 100 years.

A comparison with figures collected in 1904 have revealed that around 400 species are now extinct, including the black-veined white butterfly, not seen since 1912, the Essex emerald moth and the short-haired bumblebee. Many others are endangered, including the large garden bumblebee, the Fen Raft spider, which is only to be found in a reserve on the Norfolk/Suffolk border, and the once common scarlet malachite beetle, now restricted to just three sites.

Changes to the insects’ natural habitats have been responsible for this disastrous decline in numbers. From housing and industrial developments to single-crop farming methods, Britain’s countryside has become increasingly inhospitable to its native insects.”

I chose to talk about “Forest and woodland insects: Down and out or on the up?” I used data from that most valuable of data sets, the Rothamsted Insect Survey to illustrate my hypothesis that those insects associated with trees were either doing better or not declining, because of increased tree planting over the last fifty years.  As you can see from the slides from my talk, this does indeed seem to be the case with moths and aphids that feed on trees or live in their shade.  I also showed that the populations of the same species in northern Britain, where agriculture is less intensive and forests and woodlands more prevalent were definitely on the up, and this phenomenon was not just confined to moths and aphids.

Two tree aphids, one Drepanosiphum platanoidis lives on sycamore, the other Elatobium abietinum, lives on spruce trees; both are doing rather well.

Two more tree-dwelling aphids, one on European lime, the other on sycamore and maples, both doing very well.  For those of you unfamiliar with UK geography, East Craigs is in Scotland and Newcastle in the North East of England, Hereford in the middle and to the west, and Starcross in the South West, Sites 2, 1, 6 and 9 in the map in the preceding figure.

Two conifer feeding moth species showing no signs of decline.

On the up, two species, a beetle, Agrilus biguttatus perhaps due to climate change, and a butterfly, the Speckled Wood Pararge aegeria, due to habitat expansion and climate change?

It is important however, to remember that insect populations are not static, they vary from year to year, and the natural fluctuations in their populations can be large and, as in the case of the Orange ladybird, Halyzia sedecimguttata, take place over a several years, which is yet another reason that we need long-term data sets.

The Orange ladybird Halyzia sedecimguttata, a mildew feeder, especially on sycamore.

It is obvious, whether we believe that an ecological catastrophe is heading our way or not, that humans are having a marked effect on the biodiversity that keeps our planet in good working order and not just through our need to feed an ever-increasing population.  A number of recent studies have shown that our fixation with car ownership is killing billions of insects every year (Skórka et al., 2013; Baxter-Gilbert et al.,2015; Keilsohn et al., 2018) and that our fear of the dark is putting insects and the animals that feed on them at risk (Eccard et al.,  2018; Grubisic et al., 2018).  We have a lot to answer for and this is exacerbated by our growing disconnect from Nature and the insidious effect of “shifting baselines” which mean that succeeding generations tend to accept what they see as normal (Leather & Quicke, 2010, Soga & Gaston, 2018) and highlights the very real need for robust long-term data to counteract this dangerous and potentially lethal, World view (Schuh, 2012; Soga & Gaston, 2018).  Perhaps if research funding over the last thirty years or so had been targeted at the many million little things that run the World and not the handful of vertebrates that rely on them (Leather, 2009), we would not be in such a dangerous place?

I am, however, determined to remain hopeful.  As a result of the article in The Observer, I received an email from a gentleman called Glyn Brown, who uses art to hopefully, do something about shifting baselines.  This is his philosophy in his own words and pictures.

 

References

Baxter-Gilbert, J.H., Riley, J.L., Neufeld, C.J.H., Litzgus, J.D. & Lesbarrères, D.  (2015) Road mortality potentially responsible for billions of pollinating insect deaths annually. Journal of Insect Conservation, 19, 1029-1035.

Brooks, D.R., Bater J.E., Clark, S.J., Monteith, D.T., Andrews, C., Corbett, S.J., Beaumont, D.A. & Chapman, J.W. (2012)  Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss in insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Conrad, K.F., Warren. M.S., Fox, R., Parsons, M.S. & Woiwod, I.P. (2006) Rapid declines of common, widespread British moths provide evidence of an insect biodiversity crisis. Biological Conservation, 132, 279-291.

Eccard, J.A., Scheffler, I., Franke, S. & Hoffmann, J. (2018) Off‐grid: solar powered LED illumination impacts epigeal arthropods. Insect Conservation & Diversity, https://onlinelibrary.wiley.com/doi/full/10.1111/icad.12303

Estay, S.A., Lima, M., Labra, F.A. & Harrington, R. (2012) Increased outbreak frequency associated with changes in the dynamic behaviour of populations of two aphid species. Oikos, 121, 614-622.

Grubisic, M., van Grunsven, R.H.A.,  Kyba, C.C.M.,  Manfrin, A. & Hölker, F. (2018) Insect declines and agroecosystems: does light pollution matter? Annals of Applied Biology,   https://onlinelibrary.wiley.com/doi/full/10.1111/aab.12440

Keilsohn, W., Narango, D.L. & Tallamy, D.W. (2018) Roadside habitat impacts insect traffic mortality.  Journal of Insect Conservation, 22, 183-188.

Leather, S.R. (2009) Taxonomic chauvinism threatens the future of entomology. Biologist, 56, 10-13.

Leather, S.R. (2018) “Ecological Armageddon” –  more evidence for the drastic decline in insect numbers. Annals of Applied Biology, 172, 1-3.

Leather, S.R. & Quicke, D.J.L. (2010) Do shifting baselines in natural history knowledge therten the environment? The Environmentalist, 30, 1-2.

Schuh, S. (2012) Archives and conservation biology. Pacific Conservation Biology, 18, 223-224.

Schuh, S., Wesche, K. & Schaefer, M. (2012a) Long-term decline in the abundance of leafhoppers and planthoppers (Auchenorrhyncha) in Central Europe protected dry grasslands. Biological Conservation, 149, 75-83.

Schuh, S., Bock, J., Krause, B., Wesche, K. & Scgaefer, M. (2012b) Long-term population trends in three grassland insect groups: a comparative analysis of 1951 and 2009. Journal of Applied Entomology, 136, 321-331.

Skórka, P., Lenda, M., Moroń, D., Kalarus, K., & Tryjanowskia, P. (2013) Factors affecting road mortality and the suitability of road verges for butterflies. Biological Conservation, 159, 148-157.

Soga, M. & Gaston, K.J. (2018) Shifting baseline syndrome: causes, consequences and implications. Frontiers in Ecology & the Environment, 16, 222-230.

 

“Ecological Armageddon”, we’ve known for years that insects are in decline so why so much fuss now?

Unless you have lived in a news vacuum for the last two weeks or so, you will be aware of the impending “Ecological Armageddon” that is about to be unleashed upon us.  A paper in the journal PLoS ONE  in which it was reported that there had been a 75% decline in the biomass of flying insects in protected areas in Germany since 1989 was the starting pistol that began the media frenzy.  The newspapers, both broadsheet and tabloids were quick to react as were the radio and TV stations and the coverage was global as this selection of links shows.

https://www.nytimes.com/2017/10/29/opinion/insect-armageddon-ecosystem-.html

https://www.theguardian.com/environment/2017/oct/18/warning-of-ecological-armageddon-after-dramatic-plunge-in-insect-numbers

http://www.independent.co.uk/news/science/flying-insects-numbers-drop-ecological-armageddon-75-per-cent-plummet-a8008406.html

http://www.express.co.uk/news/science/868283/Armageddon-end-of-the-world-Germany-insects-Sussex-University-UK-Government

https://www.hs.fi/ulkomaat/art-2000005414880.html

https://risingsunoverport.co.za/53144/enviro-monday-flying-insect-populations-declining-drastically-germany/

https://www.washingtonpost.com/world/europe/buzz-off-german-study-finds-dramatic-insect-decline/2017/10/19/6a087d40-b4c8-11e7-9b93-b97043e57a22_story.html?utm_term=.00836ee55dca

Entomologists were in great demand for a few days, all being asked to comment gravely on the paper and its implications.   I was also persuaded to air my thoughts on air, Talk Radio having caught me at an unguarded moment.  I should never have answered the ‘phone 😊

As the media frenzy subsided, the more considered responses began to appear.  Manu Saunders very sensibly attempted to put the study in perspective and point out its limitations. Two entomologists from the Game & Wildlife Conservancy Trust which hold an even longer data set, put forward their interpretation and an ecological consultancy also took the opportunity to comment.  The authors of the paper and the blog commentators were careful not to point the finger directly at pesticides as the main cause of this decline, although they did rule out climate change.  Agricultural intensification and the practices associated with it, were however, suggested as likely to be involved in some way, something that has been known for more than a century as the naturalist and novelist Gene Stratton-Porter  pointed out in 1909  in her novel A Girl of the Limberlost,

 “Men all around were clearing available land.  The trees fell wherever corn would grow. The swamp was broken by several gravel roads…Wherever the trees fell the moisture dried, the creeks ceased to flow, the river ran low, and at times the bed was dry.  From coming in with two or three dozen rare moths a day, in three years time Elnora had grown to be delighted with finding two or three. Big pursy caterpillars could not be picked from their favourite bushes, where there were no bushes. Dragonflies could not hover over dry places and butterflies became scare in proportion to the flowers”.

What puzzles me about the media response is why now and why this particular study?  We have known for a long time that some insect groups have been in decline for many years.  The parlous state of UK butterflies and moths has been highlighted on more than one occasion over the last couple of decades (e.g. Conrad et al., 2004; Thomas et al., 2004; Fox et al., 2013), and declines in the abundance of bibionid flies (D’Arcy-Burt & Blackshaw, 1987), dragonflies (Clausnitzer et al., 2009) and carabid beetles (Brooks et al., 2012) have also been noticed and written about.  In addition, the results of a 42-year study on insects associated with cereal fields in SE England was published recently (Ewald et al., 2015), with little or no fanfare associated with it.  I commented on the decline of some insect species (and entomologists) in a blog post in 2013 and in December of last year, wrote about the general decline of insect numbers and lack of long term studies, incidentally citing the German study when it was originally published in a little known German publication back in 2013 and with far fewer authors 😊

The media response to this not new news puts me in mind of the Ash Die Back scare of 2012 when the press and politicians having

Pests and diseases recorded as entering the UK 1960-2015.  The two arrows indicate the replacement of local forest offices with central district offices and reduction in entomology and pathology staff.

been warned and made aware of the increasing incidence of non-native pests and pathogens entering the country for many years beforehand, suddenly, and in response to an intractable problem, went overboard in reporting doom and destruction

https://www.theguardian.com/environment/2012/nov/09/ash-dieback-disease-impossible-eradicate

https://www.theguardian.com/environment/2012/oct/24/ash-dieback-disease-east-anglia

http://www.telegraph.co.uk/news/earth/earthnews/9566224/Deadly-fungus-in-Ash-trees-could-be-next-Dutch-elm-disease-warns-Woodland-Trust.html

http://www.abc.net.au/am/content/2012/s3620359.htm

My hypothesis, for what it is worth, is that it is like when a tap washer starts to wear out, and your tap starts to drip. At first you just ignore it or turn the tap ever more tightly every time you use it.  Eventually something gives, either the tap breaks off (this happened to me very recently) or the drip becomes a flood.  Either way, something needs to be done, i.e. call the plumber.  In the case of the Ash Die Back episode, the UK government responded positively, albeit too late to prevent it, but by setting up the Tree Health and Plant Biosecurity Expert Taskforce of which I was privileged to be a member, recommendations were made that resulted in increased forest research funding and additional legislation being put in force to hopefully reduce the chances of further invasions.  I suspect that the current “Ecological Armageddon” scenario will not result in a similar response, although it may encourage research councils worldwide to think more seriously about funding more research into sustainable agriculture and for governments to encourage farmers to adopt farming strategies that encourage more wildlife and use fewer inputs.  At the same time, given the increasing number of studies that implicate urbanisation as a major factor in the decline of insect numbers (e.g. Jones & Leather, 2012; Dennis et al., 2017) it would behove local planning authorities to increase their efforts to provide much-needed green spaces in our towns and cities and to ban the use of decking in gardens and the replacement of front gardens with concrete and tarmac car parking areas.

What it does highlight as Manu Saunders said in her blog, is that we need funding for more long-term studies.  We also need to find instances where the data already exist but have not yet been analysed, amateur records and citizen science projects may be of use here.  Alternatively, as was very recently done in France (Alignier, 2018), it is possible, using the identical protocol, to resample a site after a gap of decades, to see what changes have occurred.

I hope for the sake of our descendants that the reports of an “Ecological Armageddon” have been exaggerated.  This should however, be a wake-up call to all those with the power to do something to mitigate the decline in biodiversity worldwide.  Governments need to respond quickly and to think long-term and responsibly.  The current attitude of politicians to adopt a short-term ‘how safe is my job’ political viewpoint is no longer a viable one for the planet. It is precisely that attitude that got us into the situation that we find ourselves in now.

References

Alignier, A. (2018) Two decades of change in a field margin vegetation metacommunity as a result of field margin structure and management practice changes. Agriculture, Ecosystems & Environment, 251, 1-10.

Brooks, D.R., Bater, J.E., Clark, S.J., Montoth, D.J., Andrews, C., Corbett, S.J., Beaumont, D.A., & Chapman, J.W. (2012) Large carabid beetle declines in a United Kingdom monitoring network increases evidence for a widespread loss of insect biodiversity. Journal of Applied Ecology, 49, 1009-1019.

Clausnitzer, V., Kalkman, V.J., Ram, M., Collen, B., Baillie, J.E.M., Bedjanic, M., Darwall, W.R.T., Dijkstra, K.D.B., Dow, R., Hawking, J., Karube, H., Malikova, E., Paulson, D., Schutte, K., Suhling, F., Villaneuva, R.J., von Ellenrieder, N. & Wilson, K. (2009)  Odonata enter the biodiversity crisis debate: the first global assessment of an insect group.  Biological Conservation, 142, 1864-1869.

Conrad, K.F., Woiwod, I.P., Parsons, M., Fox, R. & Warren, M.S. (2004) Long-term population trends in widespread British moths.  Journal of Insect Conservation, 8, 119-136.

Darcy-Burt, S. & Blackshaw, R.P. (1987) Effects of trap design on catches of grassland Bibionidae (Diptera: Nematocera).  Bulletin of Entomological Research, 77, 309-315.

Dennis, E.B., Morgan, B.J.T., Roy, D.B. & Brereton, T.M. (2017) Urban indicators for UK butterflies. Ecological Indicators, 76, 184-193.

Ewald, J., Wheatley, C.J., Aebsicher, N.J., Moreby, S.J., Duffield, S.J., Crick, H.Q.P., & Morecroft, M.B. (2015) Influences of extreme weather, climate and pesticide use on invertebrates in cereal fields over 42 years. Global Change Biology, 21, 3931-3950.

Fox, R. (2013) The decline of moths in Great Britain: a review of possible causes. Insect Conservation & Diversity, 6, 5-19.

Hallmann, C.A., Sorg, M., Jongejans, E., Siepel, H., Hofland, N., Schwan, H., Stenmans, W., Müller, A., Sumser, H., Hörren, T., Goulson, D. & de Kroon, H. (2017) More than 75% decline over 27 years in total flying insect biomass in protected areas. PLoS ONE. 12 (10):eo185809.

Jones, E.L. & Leather, S.R. (2012) Invertebrates in urban areas: a review.  European Journal of Entomology, 109, 463-478.

Knowler, J.T., Flint, P.W.H., & Flint, S. (2016) Trichoptera (Caddisflies) caught by the Rothamsted Light Trap at Rowardennan, Loch Lomondside throughout 2009. The Glasgow Naturalist, 26, 35-42.

Thomas, J.A., Telfer, M.G., Roy, D.B., Preston, C.D., Greenwood, J.J.D., Asher, J., Fox, R., Clarke, R.T. & Lawton, J.H. (2004) Comparative losses of British butterflies, birds, and plants and the global extinction crisis.  Science, 303, 1879-1883.