In­sect apoca­lypse

Bugs dis­ap­pear­ing around the world

Irish Examiner - - Front Page -

In­sects are the vi­tal pol­li­na­tors and re­cy­clers of ecosys­tems and the base of food webs ev­ery­where.

In the US, sci­en­tists re­cently found the pop­u­la­tion of monarch but­ter­flies fell by 90% in the last 20 years; the rusty-patched bum­ble­bee, which once lived in 28 states, dropped by 87% over the same pe­riod.

A 2017 pa­per by an ob­scure Ger­man en­to­mo­log­i­cal so­ci­ety brought the prob­lem of in­sect de­cline into sharp fo­cus. The study found that, mea­sured sim­ply by weight, the over­all abun­dance of fly­ing in­sects in Ger­man na­ture re­serves had de­creased by 75% over just 27 years.

If you looked at mid­sum­mer pop­u­la­tion peaks, the drop was 82%. The study would quickly be­come, ac­cord­ing to the web­site Alt­met­ric, the sixth-most-dis­cussed sci­en­tific pa­per of 2017.

Head­lines around the world warned of an “in­sect Ar­maged­don”. How could some­thing as fun­da­men­tal as the bugs in the sky just dis­ap­pear? And what would be­come of the world with­out them?

We’ve named and de­scribed a mil­lion species of in­sects. There are 12,000 types of ants, nearly 20,000 va­ri­eties of bees, al­most 400,000 species of bee­tles.

And yet en­to­mol­o­gists es­ti­mate that all this amaz­ing, ab­surd, and un­der­stud­ied va­ri­ety rep­re­sents per­haps only 20% of the ac­tual diver­sity of in­sects on our planet — that there are mil­lions and mil­lions of species that are en­tirely un­known to sci­ence.

When en­to­mol­o­gists be­gan notic­ing and in­ves­ti­gat­ing in­sect de­clines, they lamented the ab­sence of solid in­for­ma­tion from the past in which to ground their ex­pe­ri­ences of the present.

“We see a hun­dred of some­thing, and we think we’re fine,” says David Wag­ner, an en­to­mol­o­gist at the Univer­sity of Con­necti­cut, “but what if there were 100,000 two gen­er­a­tions ago?”

Rob Dunn, an ecol­o­gist at North Carolina State Univer­sity, re­cently searched for stud­ies show­ing the ef­fect of pes­ti­cide spray­ing on the quan­tity of in­sects liv­ing in nearby forests.

He was sur­prised to find that no such stud­ies ex­isted. “We ig­nored ba­sic ques­tions,” he said. “It feels like we’ve dropped the ball in some gi­ant col­lec­tive way.”

If en­to­mol­o­gists lacked data, what they did have were some very wor­ry­ing clues. A 2014 re­view in Sci­ence syn­the­sized the find­ings of ex­ist­ing stud­ies and found that a ma­jor­ity of mon­i­tored species were de­clin­ing, on av­er­age by 45%.

There were stud­ies of other, bet­terun­der­stood species that sug­gested the in­sects as­so­ci­ated with them might be de­clin­ing, too. Peo­ple who stud­ied fish found that the fish had fewer mayflies to eat.

Or­nithol­o­gists kept finding that birds that rely on in­sects for food were in trou­ble: Half of all farm­land birds in Europe dis­ap­peared in just three decades. At first, many sci­en­tists as­sumed the fa­mil­iar cul­prit of habi­tat de­struc­tion was at work, but then they be­gan to won­der if the birds might sim­ply be starv­ing.

The signs were cer­tainly alarm­ing, but they were also just signs, not enough to jus­tify grand pro­nounce­ments about the health of in­sects as a whole or about what might be driv­ing a wide­spread, cross-species de­cline.

“There are no quan­ti­ta­tive data on in­sects, so this is just a hy­poth­e­sis,” said Hans de Kroon, an ecol­o­gist at Rad­boud Univer­sity in the Nether­lands.

Then came the Ger­man study. Sci­en­tists are still cau­tious about what the find­ings might im­ply about other re­gions of the world. But the study brought forth ex­actly the kind of lon­gi­tu­di­nal data they had been seek­ing, and it wasn’t spe­cific to just one type of in­sect.

The num­bers were stark, in­di­cat­ing a vast im­pov­er­ish­ment of an en-

The num­bers are stark, in­di­cat­ing a vast im­pov­er­ish­ment of an en­tire in­sect uni­verse, writes Brooke Jarvis

tire in­sect uni­verse, even in pro­tected ar­eas where in­sects ought to be un­der less stress. The speed and scale of the drop were shock­ing even to en­to­mol­o­gists who were al­ready anx­ious about bees or fire­flies.

The re­sults were sur­pris­ing in an­other way too. The long-term de­tails about in­sect abun­dance, the kind that no one re­ally thought ex­isted, hadn’t ap­peared in a par­tic­u­larly pres­ti­gious jour­nal and didn’t come from univer­sity-af­fil­i­ated sci­en­tists, but from a small so­ci­ety of in­sect en­thu­si­asts based in the mod­est Ger­man city of Krefeld.

In 2013, Krefeld en­to­mol­o­gists con­firmed the to­tal num­ber of in­sects caught in one na­ture re­serve was nearly 80% lower than the same spot in 1989. They had sam­pled other sites, an­a­lysed old data sets, and found sim­i­lar de­clines: Where 30 years ear­lier, they of­ten needed a litre bot­tle for a week of trap­ping, now a 500ml bot­tle usu­ally suf­ficed.

But it would have taken even highly trained en­to­mol­o­gists years of painstak­ing work to iden­tify all the in­sects in the bot­tles. So the so­ci­ety used a stan­dard­ised method for weigh­ing in­sects in al­co­hol, which told a pow­er­ful story sim­ply by show­ing how much the over­all mass of in­sects dropped over time.

The so­ci­ety col­lab­o­rated with de Kroon and other sci­en­tists at Rad­boud Univer­sity in the Nether­lands, who did a trend anal­y­sis of the data that Krefeld pro­vided, con­trol­ling for things like the ef­fects of nearby plants, weather, and for­est cover on fluc­tu­a­tions in in­sect pop­u­la­tions.

The fi­nal study looked at 63 na­ture pre­serves, rep­re­sent­ing al­most 17,000 sam­pling days, and found consistent de­clines in ev­ery kind of habi­tat they sam­pled. This sug­gested, the authors wrote, “that it is not only the vul­ner­a­ble species but the fly­ing-in­sect com­mu­nity as a whole that has been dec­i­mated over the last few decades.”

The cur­rent world­wide loss of bio­di­ver­sity is pop­u­larly known as the sixth ex­tinc­tion: The sixth time in world his­tory that a large num­ber of species have dis­ap­peared in un­usu­ally rapid suc­ces­sion, caused this time not by as­ter­oids or ice ages but by hu­mans.

What we’re los­ing is not just the diver­sity part of bio­di­ver­sity, but the bio part: Life in sheer quan­tity. While I was writ­ing this ar­ti­cle, sci­en­tists learned that the world’s largest king pen­guin colony shrank by 88% in 35 years, that more than 97% of the bluefin tuna that once lived in the ocean are gone.

Finding re­as­sur­ance in the sur­vival of a few sym­bolic stan­dard­bear­ers ig­nores the value of abun­dance, of a nat­u­ral world that thrives on rich­ness and com­plex­ity and in­ter­ac­tion.

Tigers still ex­ist, for ex­am­ple, but that doesn’t change the fact that 93% of the land where they used to live is now tiger­less. This mat­ters for more than ro­man­tic rea­sons: Large an­i­mals, es­pe­cially top preda­tors like tigers, con­nect ecosys­tems to one an­ing other and move en­ergy and re­sources among them sim­ply by walk­ing and eat­ing and defe­cat­ing and dy­ing.

One re­sult of their loss is what’s known as trophic cas­cade, the un­rav­el­ling of an ecosys­tem’s fab­ric as prey pop­u­la­tions boom and crash and the var­i­ous lev­els of the food web no longer keep each other in check.

Sci­en­tists have be­gun to speak of func­tional ex­tinc­tion. Func­tion­ally ex­tinct an­i­mals and plants are still present but no longer preva­lent enough to af­fect how an ecosys­tem works.

Some phrase this as the ex­tinc­tion not of a species but of all its for­mer in­ter­ac­tions with its en­vi­ron­ment — an ex­tinc­tion of seed dis­per­sal and pre­da­tion and pol­li­na­tion and all the other eco­log­i­cal func­tions an an­i­mal once had, which can be dev­as­tat­ing even if some in­di­vid­u­als still per­sist.

The more in­ter­ac­tions are lost, the more dis­or­dered the ecosys­tem be­comes. A 2013 pa­per in Na­ture, which mod­elled both nat­u­ral and com­put­er­gen­er­ated food webs, sug­gested that a loss of even 30% of a species’ abun­dance can be so desta­bil­is­ing that other species start go­ing fully, nu­mer­i­cally ex­tinct.

In ad­di­tion to ex­tinc­tion (the com­plete loss of a species) and ex­tir­pa­tion (a lo­calised ex­tinc­tion), sci­en­tists now speak of de­fau­na­tion: The loss of in­di­vid­u­als, the loss of abun­dance, the loss of a place’s ab­so­lute an­i­mal­ness.

In a 2014 ar­ti­cle in Sci­ence, re­searchers ar­gued that the word should be­come as fa­mil­iar, and in­flu­en­tial, as the con­cept of de­for­esta­tion. In 2017, an­other pa­per re­ported that ma­jor pop­u­la­tion and range losses ex­tended even to species con­sid­ered to be at low risk for ex­tinc­tion.

They pre­dicted “neg­a­tive cas­cadreally con­se­quences on ecosys­tem func­tion­ing and ser­vices vi­tal to sus­tain­ing civil­i­sa­tion” and of­fered an­other term for the wide­spread loss of the world’s wild fauna: “Bi­o­log­i­cal an­ni­hi­la­tion.”

Sci­en­tists have tried to calculate the ben­e­fits that in­sects pro­vide. Tril­lions of bugs flit­ting from flower to flower pol­li­nate some three-quar­ters of our food crops, a ser­vice worth as much as €500bn ev­ery year. (This doesn’t count the 80% of wild flow­er­ing plants, the foun­da­tion blocks of life ev­ery­where, that rely on in­sects for pol­li­na­tion.)

If mon­e­tary cal­cu­la­tions like that sound strange, con­sider the Maox­ian Val­ley in China, where short­ages of in­sect pol­li­na­tors have led farm­ers to hire hu­man work­ers, at a cost of up to $19 per worker per day, to re­place bees. Each per­son cov­ers five to 10 trees a day, pol­li­nat­ing ap­ple blos­soms by hand.

By eat­ing and be­ing eaten, in­sects turn plants into pro­tein and power the growth of all the un­count­able species — in­clud­ing fresh­wa­ter fish and a ma­jor­ity of birds — that rely on them for food, not to men­tion all the crea­tures that eat those crea­tures.

We worry about sav­ing the griz­zly bear, says the in­sect ecol­o­gist Scott Hoffman Black, but where is the griz­zly with­out the bee that pol­li­nates the berries it eats or the flies that sus­tain baby sal­mon? Where, for that mat­ter, are we?

Bugs are vi­tal to the de­com­po­si­tion that keeps nu­tri­ents cy­cling, soil healthy, plants grow­ing, and ecosys­tems run­ning. When asked to imag­ine what would hap­pen if in­sects were to dis­ap­pear com­pletely, sci­en­tists find words like chaos, col­lapse, Ar­maged­don.

Wag­ner de­scribes a flow­er­less world with silent forests, a world of dung and old leaves and rot­ting car­casses ac­cu­mu­lat­ing in cities and road­sides, a world of “col­lapse or de­cay and ero­sion and loss that would spread through ecosys­tems” — spi­ralling from preda­tors to plants.

EO Wil­son has writ­ten of an in­sect­free world, a place where most plants and land an­i­mals be­come ex­tinct; where fungi ex­plodes, for a while, thriv­ing on death and rot; and where “the hu­man species sur­vives, able to fall back on wind-pol­li­nated grains and ma­rine fish­ing” de­spite mass star­va­tion and re­source wars.

In Oc­to­ber, an en­to­mol­o­gist sent me an email with the sub­ject line, “Holy [ex­ple­tive]!” and an at­tach­ment: A study just out from Pro­ceed­ings of the Na­tional Acad­emy of Sci­ences that he la­belled, “Krefeld comes to Puerto Rico.”

The study in­cluded data from the 1970s and from the early 2010s, when a trop­i­cal ecol­o­gist named Brad Lis­ter re­turned to the rain for­est where he had stud­ied lizards — and, cru­cially, their prey — 40 years ear­lier.

Lis­ter set out sticky traps and swept nets across fo­liage in the same places he had in the 1970s, but this time he and his co-au­thor, An­dres Gar­cia, caught much, much less: Ten­fold to six­ty­fold less arthro­pod biomass than be­fore.

Even scarier were the ways the losses were al­ready mov­ing through the ecosys­tem, with se­ri­ous de­clines in the num­bers of lizards, birds, and frogs. The pa­per re­ported “a bot­tomup trophic cas­cade and con­se­quent col­lapse of the for­est food web”.

Like other species, in­sects are re­spond­ing to what Chris Thomas, an in­sect ecol­o­gist at the Univer­sity of York, has called “the trans­for­ma­tion of the world”: not just a chang­ing cli­mate but also the wide­spread con­ver­sion, via ur­ban­i­sa­tion, agri­cul­tural in­ten­si­fi­ca­tion, and so on, of nat­u­ral spa­ces into hu­man ones, with fewer and fewer re­sources “left over” for non-hu­man crea­tures to live on. What re­sources re­main are of­ten con­tam­i­nated.

Hans de Kroon char­ac­terises the life of many mod­ern in­sects as try­ing to sur­vive from one dwin­dling oa­sis to the next but with “a desert in be­tween, and at worst it’s a poi­sonous desert”.

Of par­tic­u­lar con­cern are neon­i­coti­noids, neu­ro­tox­ins that were thought to af­fect only treated crops but turned out to ac­cu­mu­late in the land­scape and to be con­sumed by all kinds of non­tar­geted bugs. Peo­ple talk about the “loss” of bees to colony col­lapse dis­or­der, and that ap­pears to be the right word: Af­fected hives aren’t full of dead bees, but sim­ply mys­te­ri­ously empty. A lead­ing the­ory is that ex­po­sure to neu­ro­tox­ins leaves bees un­able to find their way home.

Even hives ex­posed to low lev­els of neon­i­coti­noids have been shown to col­lect less pollen and pro­duce fewer eggs and far fewer queens. Some re­cent stud­ies found bees do­ing bet­ter in cities than in the sup­posed coun­try­side.

Since the Krefeld data emerged, there have been hear­ings about pro­tect­ing in­sect bio­di­ver­sity in the Ger­man Bun­destag and the Euro­pean Par­lia­ment. EU mem­ber states voted to ex­tend a ban on neon­i­coti­noid pes­ti­cides and have be­gun to put money to­wards fur­ther stud­ies of how abun­dance is chang­ing, what is caus­ing those changes and what can be done.

Stem­ming in­sect de­clines will re­quire much more, how­ever. The EU al­ready had some mea­sures in place to help pol­li­na­tors — in­clud­ing more strictly reg­u­lat­ing pes­ti­cides than the US does and pay­ing farm­ers to cre­ate in­sect habi­tats by leav­ing fields fal­low and al­low­ing for wild edges along­side cul­ti­va­tion — but in­sect pop­u­la­tions dropped any­way.

New re­ports call for na­tional gov­ern­ments to col­lab­o­rate; for more cre­ative ap­proaches such as in­te­grat­ing in­sect habi­tats into the de­sign of roads, power lines, rail­roads and other in­fra­struc­ture; and, as al­ways, for more stud­ies.

The nec­es­sary changes, like the causes, may be pro­found. “It’s just an­other in­di­ca­tion that we’re de­stroy­ing the life-sup­port sys­tem of the planet,” Lis­ter says of the Puerto Rico study. “Na­ture’s re­silient, but we’re push­ing her to such ex­tremes that even­tu­ally it will cause a col­lapse of the sys­tem.”

Sci­en­tists hope that in­sects will have a chance to em­body that re­silience. A ghost moth in Aus­tralia was once recorded lay­ing 29,100 eggs, and she still had 15,000 in her ovaries. The fe­cund abun­dance that is in­sects’ sin­gu­lar trait should en­able them to re­cover, but only if they are given the space and the op­por­tu­nity to do so.

■ Adapted from an ar­ti­cle that orig­i­nally ap­peared in New York Times Mag­a­zine

■ c.2018 The New York Times

>> In­sects are the vi­tal pol­li­na­tors and re­cy­clers of ecosys­tems and the base of food webs ev­ery­where.


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