The Road to Re­cov­ery

The Ch­er­nobyl Ex­clu­sion Zone and Bikini Atoll are still devoid of hu­mans. But with­out the threat of our pres­ence, could wildlife thrive in a ra­dioac­tive en­vi­ron­ment?

BBC Earth (Asia) - - Contents - WORDS BY ALLA KAT­SNEL­SON

Can wildlife thrive in a ra­dioac­tive en­vi­ron­ment?

Early this year, the Dooms­day Clock ticked for­wards to two min­utes to apoc­a­lypse – the clos­est it’s been since 1953 when the US and the Soviet Union tested hy­dro­gen bombs. The Bul­letin

Of The Atomic Sci­en­tists opted to move the clock for­wards due to growing con­cerns about po­ten­tial nu­clear war, whether such events be borne of strife be­tween the US and North Korea, Pak­istan and In­dia, or some other cri­sis point.

In the past, we have seen the im­me­di­ate ef­fects of ra­di­a­tion, through nu­clear bombs or power sta­tion fail­ures. By vis­it­ing ra­dioac­tive sites like these, en­ter­pris­ing sci­en­tists can find out about the long-term im­pact of ra­di­a­tion on the en­vi­ron­ment, so we know what to ex­pect in the event that some­one pushes the big red but­ton.

GO­ING NU­CLEAR

One place that might of­fer some clues is Bikini Atoll, a ring-shaped co­ral reef lo­cated in the Mar­shall Is­lands. In 1946, the US evac­u­ated Bikini’s res­i­dents, then spent 12 years test­ing its nu­clear fire­power by det­o­nat­ing 23 nu­clear bombs there, in­clud­ing one that packed 1,000 times the power of the one that dev­as­tated Hiroshima and was the largest nu­clear de­vice that the US ever ex­ploded. It’s a place, you might think, that’d be com­pletely devoid of life to this day.

But in 2016, Steve Palumbi, pro­fes­sor of ma­rine sciences at Stan­ford Univer­sity in Cal­i­for­nia, vis­ited Bikini to doc­u­ment the ma­rine life. He first got in­ter­ested in Bikini while re­search­ing his book The Ex­treme Life Of

The Sea. He learned that the age of or­gan­isms could be de­ter­mined by mea­sur­ing their ar­ti­fi­cial car­bon-14 lev­els caused by hy­dro­gen bomb tests in the mid­dle of the last cen­tury. So when he was in­vited by the US tele­vi­sion sta­tion PBS to do a doc­u­men­tary se­ries called The Big

Pa­cific, he told the pro­duc­ers that he wanted to go to Bikini Atoll.

Rather than find­ing it bar­ren, he dis­cov­ered a di­verse ar­ray of species in­clud­ing co­rals, fish, sharks and crabs thriv­ing in the atoll’s waters. Un­doubt­edly, the com­plete ab­sence of hu­mans for more than seven decades has helped cre­ate an undis­turbed ter­ri­tory in which wildlife could flour­ish.

“When you started look­ing at the re­ports and hints, we were ex­pect­ing to see some re­cov­ery – we just had no idea how ex­ten­sive,” he says. And ac­cord­ing to his team’s ob­ser­va­tions, the or­gan­isms ap­peared quite nor­mal, with no ob­vi­ous mu­tant char­ac­ter­is­tics. “There are a lot of strange things there – like co­conuts the size and shape of zuc­chi­nis [cour­gettes] on the trees,” he says. “But can you re­ally pin these things on ra­di­a­tion? It’s not all that clear.”

Ukraine pro­vides another ex­am­ple of the sur­pris­ing ways that life can re­cover after ex­po­sure to ra­di­a­tion. Early on 26 April 1986, re­ac­tor 4 of the Ch­er­nobyl nu­clear power plant ex­ploded, due to a fa­tal com­bi­na­tion of en­gi­neer­ing glitch and hu­man er­ror. Be­tween the ex­plo­sion and the sub­se­quent fire, which raged for 10 days, the ac­ci­dent spewed about 400 times more ra­dioac­tive ma­te­rial into the at­mos­phere than what was re­leased by the Hiroshima and Na­gasaki bombs com­bined. Ul­ti­mately, of­fi­cials evac­u­ated some 330,000 peo­ple from the re­gion and es­tab­lished a so-called Ch­er­nobyl Ex­clu­sion Zone that to­day cov­ers about 4,200km2, graded by four lev­els of con­tam­i­na­tion.

“We don’t re­ally know very much about what went on right after the dis­as­ter at Ch­er­nobyl, other than the fact that ev­ery­thing was wiped out for many miles – ev­ery­thing from trees, to mam­mals, to in­sects,” says Prof Ti­mothy Mousseau, a bi­ol­o­gist at the Univer­sity of South Carolina.

ROAD TO RE­COV­ERY

In the decades since, re­searchers have watched the re­gion closely for signs of re­cov­ery. Prof Jim Smith, an en­vi­ron­men­tal sci­en­tist at the Univer­sity of Portsmouth, has worked with sci­en­tists from Be­larus to mon­i­tor some of the mam­mals that live in the zone, such as wild boar, elk and wolves. Sur­pris­ingly, he says, pop­u­la­tions seem to have bounced back, both in terms of abun­dance and di­ver­sity. As Smith ex­plains, con­tam­i­na­tion within the zone is un­even: about 1 per cent of the re­gion con­sists of ar­eas like the in­fa­mous Red For­est, with its off-the-chart ra­di­a­tion lev­els, while much lower lev­els ex­ist else­where. But even in the hotspots, he and his col­lab­o­ra­tors have seen no de­crease in pop­u­la­tion num­bers of big mam­mals (ex­cept wolves) com­pared to nearby ra­di­a­tion-free na­ture re­serves.

So if wildlife has flour­ished in the decades after a nu­clear event, does it sug­gest that these re­gions have rapidly re­cov­ered? Ab­so­lutely not, says Palumbi about Bikini. “It looks fine, but there’s an in­vis­i­ble men­ace there,” he ex­plains. In the early 1970s, some peo­ple who had lived at Bikini Atoll be­fore the bomb tests were told they could re­turn, only to be re-evac­u­ated a few years later due to lin­ger­ing un­safe ra­di­a­tion lev­els. “If you do ex­actly what you’re not sup­posed to do and fol­low the sig­nals [of the ra­di­a­tion counter] to where it gets stronger, you end up at the wa­ter well [a fresh­wa­ter source],” he says.

“BIKINI ATOLL LOOKS FINE, BUT THERE’S AN IN­VIS­I­BLE MEN­ACE THERE”

A 2016 study that re-ex­am­ined ra­di­a­tion lev­els at the Mar­shall Is­lands con­cluded that Bikini’s con­tam­i­na­tion is higher than pre­vi­ously thought, although at other is­lands it seems to have dis­si­pated. Re­searchers con­cluded that fig­ur­ing out whether the is­lands had be­come hab­it­able would in­volve de­ter­min­ing the ra­dioac­tive dose from in­gest­ing food farmed or caught there. “Every day there were mo­ments that told you some­thing was very wrong about the place, like when the boat’s nav­i­ga­tion sys­tem screamed we had run aground be­cause it was us­ing maps from 1935, and where we were an­chored – in 49 me­tres of wa­ter – had been an is­land back then,” says Palumbi.

The story in Ch­er­nobyl is per­haps even more com­pli­cated. Mousseau points out that, for wildlife, the pres­ence of hu­mans is in some ways worse than large doses of ra­dioac­tiv­ity. This is be­cause hu­mans en­croach on the habi­tats of many an­i­mals through set­tle­ment, hunt­ing and agri­cul­ture. That’s why his team stud­ies or­gan­isms like small ro­dents, in­sects, birds and trees. As these are less in­flu­enced by the pres­ence or ab­sence of hu­mans, it gives the sci­en­tists more op­por­tu­nity to home in on the ef­fects of ra­dioac­tive con­tam­i­nants, he says.

Mousseau and his col­leagues do see prob­lems on both the pop­u­la­tion and the in­di­vid­ual level that they be­lieve stem from el­e­vated ra­di­a­tion lev­els. For ex­am­ple, they re­ported a height­ened in­ci­dence of cataracts and gen­er­ally smaller brains in birds and small mam­mals at Ch­er­nobyl. In ra­di­a­tion hotspots, 40 per cent of birds in some years were com­pletely ster­ile, they found. What’s more, while they ob­served wolves and some other an­i­mals thriv­ing, un­like Smith’s group they re­ported a lower abun­dance of in­sects, birds and mam­mals in highly ra­dioac­tive re­gions, as well as re­duced rates of growth in pine trees. They found that leaf lit­ter was thicker in ar­eas with high lev­els of con­tam­i­na­tion, which sug­gests that num­bers of de­com­posers – like bac­te­ria and fungi – are re­duced. These or­gan­isms carry out an es­sen­tial role in break­ing down or­ganic mat­ter to re­lease its car­bon and ni­tro­gen. In fact, the Red For­est it­self does not seem to be de­cay­ing prop­erly, de­spite hav­ing died off fol­low­ing the ex­plo­sion more than 30 years ago.

HOPE FOR HU­MANS

How all this trans­lates to hu­man health is far from clear. The more com­plex an or­gan­ism is – and hu­mans are rel­a­tively com­plex – the more sus­cep­ti­ble to ra­dioac­tiv­ity it is thought to be. But the main rea­son places like Bikini Atoll and Ch­er­nobyl are deemed too dan­ger­ous for us is not down to some phys­i­o­log­i­cal dif­fer­ences be­tween hu­mans and other an­i­mals, but be­cause the thresh­old of risk is set much lower for us than for wildlife. “It comes down to a po­lit­i­cal and so­ci­o­log­i­cal dis­cus­sion – not a sci­en­tific one,” Smith says. He be­lieves that the re­cent re­search sug­gests that in re­al­ity, the risk in much of the re­gion around Ch­er­nobyl now is not very high. “Or­gan­isms are used to mu­ta­tion, it’s part of life,” he says.

In truth, sci­en­tists know lit­tle about how chronic ex­po­sure to low-level ra­di­a­tion af­fects the body. One of the main planks for un­der­stand­ing the link be­tween ra­di­a­tion ex­po­sure and can­cer is the so-called Life Span Study, in which 94,000 sur­vivors of the bomb­ing of Hiroshima and Na­gasaki, 27,000 un­ex­posed in­di­vid­u­als, and their chil­dren, have been mon­i­tored since 1950. But even there, the ef­fects are less sig­nif­i­cant than most peo­ple think, Smith says. Mousseau, how­ever, ar­gues that end­points other than can­cer, like num­ber of cataracts, head size or im­mune dis­or­ders, re­veal a more nu­anced pic­ture.

But Palumbi thinks that data from Bikini Atoll could help us fill that knowl­edge gap. He plans to look at mu­ta­tion rates in or­gan­isms such as co­rals, which live a long time, and co­conut crabs, which reg­u­larly eat the most con­tam­i­nated thing on the is­land – co­conuts – to probe the ef­fect of low-dose ex­po­sure on a ge­nomic level. Mousseau, mean­while, hopes to pur­sue in-depth ge­nomic and other types of molec­u­lar stud­ies in peo­ple from near Ch­er­nobyl.

MOD­ERN NUKES

It’s hard to say how all these vari­ables con­trib­ute to the pic­ture of what might hap­pen in the case of an ex­change of nu­clear bombs to­day. The big­gest con­cern, ex­perts agree, would be im­me­di­ate. The most dev­as­tat­ing im­pact of the bombs dropped on Hiroshima and Na­gasaki was the blast and acute af­ter­math: es­ti­mates sug­gest some 135,000 and 70,000 peo­ple died, re­spec­tively, with half of the deaths oc­cur­ring on the day of the blasts and the rest of the vic­tims ex­pe­ri­enc­ing hor­rific ef­fects over the weeks and months af­ter­wards.

Ex­perts cau­tion that the im­pact would likely be ex­po­nen­tially larger for any bomb dropped to­day. “The bombs dropped on Na­gasaki and Hiroshima were itsy-bitsy tiny atomic bombs com­pared to the bombs that we have now,” says Mousseau. To­day’s bombs are about 1,000 times more pow­er­ful, and the re­ac­tions pow­er­ing them will be more ef­fi­cient.

De­pend­ing on how many bombs were dropped, and how big they were, nu­clear fall­out from the ex­plo­sion would add fur­ther con­tam­i­na­tion in the days and weeks after an ex­plo­sion. In 1983, the physi­cist Carl Sa­gan pro­posed the con­tro­ver­sial no­tion that if a nu­clear ex­plo­sion tossed enough soot and dust into the air, it could ab­sorb a sig­nif­i­cant amount of the Sun’s rays, caus­ing a nu­clear win­ter. Us­ing the same mod­els that sci­en­tists use to pre­dict the long-term ef­fects of cli­mate change, Prof Alan Robock, an en­vi­ron­men­tal sci­en­tist at Rut­gers Univer­sity in

New Jersey, has cal­cu­lated that a re­gional nu­clear war could lead to a mas­sive drop in agri­cul­tural ca­pac­ity, a re­duc­tion in tem­per­a­ture and pre­cip­i­ta­tion, and an in­crease in UV ir­ra­di­a­tion caused by the de­struc­tion of the ozone layer. “Global warm­ing would not be one of the things we’d ever worry about again,” says Mousseau.

These are just mod­els, of course, but could it hap­pen? It’s best that we never find out.

“THE BOMBS DROPPED ON NA­GASAKI AND HIROSHIMA WERE ITSY-BITSY TINY BOMBS COM­PARED TO THE BOMBS THAT WE HAVE NOW”

A white-tailed ea­gle lands on a wolf’s car­cass in­side the 30km ex­clu­sion zone sur­round­ing the Ch­er­nobyl nu­clear power plant

ABOVE: All of Bikini’s co­conut palms were de­stroyed after the nu­clear tests. The army re­planted them in a per­fect grid shape

IN­SET ABOVE:Co­conuts are one of the most con­tam­i­nated food sources on Bikini

In these thyroid can­cer cells, the ab­nor­mally large nu­cleus is coloured green. Chil­dren ex­posed to high lev­els of ra­di­a­tion fol­low­ing the Ja­panese atomic bombs had more chance of de­vel­op­ing thyroid can­cer in later life than un­ex­posed in­di­vid­u­als

ABOVE: Ac­cord­ing to some sci­en­tists, hu­mans have more of an ef­fect on large an­i­mals than ra­di­a­tion does

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