The Economist January 8th 2022 Science & technology 69hedgehogs, a species that has undergone a
precipitous decline in Britain in recent
years, and which is thus precisely the sort
of creature that is of interest to those con
ducting ecological censuses.
Aerial metagenomics does, then, seem
to work. But vertebrates, big and showy
though they are, are by no means the only
important fauna in an ecosystem. Argu
ably, insects are more so. And Fabian Rog
er, an entomologist now working at eth
Zurich, in Switzerland, has shown that the
technique works with them, too, and can
even yield novel information about an ar
ea’s inhabitants.
Dr Roger carried out his study in col
laboration with colleagues from Lund Uni
versity in Sweden when he was working
there before his move to Zurich. Lund is
just across the Oresund bridge from Co
penhagen, and it was a system similar to Dr
Lynggaard’s waterpercolation approach
that he used. One of his chosen sites was
the roof of Lund’s ecology department—a
wellestablished location for moth surveil
lance using conventional light traps. The
other was in a forest in Smaland, a prov
ince of Sweden a little to the north of Lund.
Here, the principal targets were bees and
butterflies, which in this case had been
monitored the oldfashioned way, using
the booted ecological infantry.
Dr Roger has not yet published his re
sults in a journal, but he reported them in
December at an online conference called
Ecology Across Borders. His version of the
percolation system detected a combined
total of 85 insect species at the two sites, 77
of which had been missed by more conven
tional sampling. It also recorded nine ver
tebrates (various frogs, birds and mam
mals) and lots of invertebrates other than
insects. On the other hand, it missed 81 in
sect species shown by the other methods to
have been present. It was especially bad at
moths, noting a mere nine species while
the traps caught a whopping 48. It did,
though, manage to pick up five moth spe
cies that the traps had not.
Something which surprised both Dr
Clare and Dr Lynggaard was that their zoo
quests detected not only exhibits, local
wild animals and pets, but also some spe
cies that were none of those things. Dr
Lynggaard’s equipment logged three fish:
roach, smelt and salmon. Dr Clare’s sniffed
dnafrom cows, pigs and chickens.
The probable source of these is feeding
time. Copenhagen Zoo keeps storks, seals,
sea lions, polar bears and crocodiles. All
are piscovores, and the fish Dr Lynggaard
detected are regularly on their menus. Ha
merton, meanwhile, has a proud collection
of terrestrial carnivores, including tigers,
cheetahs, lynx and maned wolves. These
frequently dine on chicken, pork and beef.
It is one thing to pick up dnafrom a liv
ing animal that is constantly shedding
hair, skin cells, sweat and, indeed, urine
and faeces. It is quite another to detect it
from an inert lump of meat—even allow
ing for that meat having been mauled
while it was being eaten. This discovery
might be used to help a branch of conserva
tion different from the habitat monitoring
that Dr Clare, Dr Lynggaard and Dr Roger
have in mind, for it could be employed to
create devices that detect species in which
international trade is illegal.
Such species are often hidden contra
band—pangolin meat on its way to market,
for example. But the technique could also
help distinguish whether something that
was being imported openly, like a cargo of
fish, was actually what it claimed to be
rather than an endangered lookalike.Early warning
Returning to the question of monitoring
wild habitats, sampling airborne dna
might give early notice of the arrival there
ofnew species—whethernaturally from
nearby,asa consequenceofthingslikecli
matechange,ormoreartificially,fromfaraway, by the introduction of an alien and
potentially disruptive organism. In the
second case, early detection might allow
action to be taken before the invader be
came established.
Conversely, dnasniffing might one day
give warning when a local species was in
trouble, though it is not yet sensitive
enough to do that. Also, as Dr Roger’s re
sults demonstrate, it works best at the mo
ment as an addition to, rather than a sub
stitution for, established methods, so ea
ger phdstudents need not fret about re
dundancy just yet.
But one thing which has proved true so
far about dnarelated technology is that it
gets better and cheaper as time passes.
Whether it will ever get to the point when
ramblers through wood and over meadow
will have to get used to the sight of dna
sniffers keeping a nose on the local ecology
remains to be seen. But the results which
Dr Lynggaard, Dr Clare and Dr Roger have
comeupwithsuggestthat such sniffers
will,attheleast,bea valuable addition to
ecologists’arsenals. nPlantbreedinginorbitGreenhouses in the sky
P
lants grownin orbit, and thereby de
prived of the comforting directional
pull of Earth’s gravity, typically struggle to
distinguish up from down. This makes it
harder for them to carry water and nutri
ents around themselves. It also fouls up
their ability to draw carbon dioxide needed
for photosynthesis from the air. The stress
caused by all this seems to increase the lev
el of genetic mutation induced by a givenamount of radiation—of which there is
much in space, in the form of cosmic rays
and effluvia from the sun. And mutations
are the lifeblood of plant breeders.
On Earth, breeders induce them by ex
posing plants and seeds to radioactive iso
topes, xrays and so on. Most are harmful.
But some hit the jackpot, conferring prop
erties like drought resistance, blight resis
tance or shorter stems, favoured by farmRadiation and microgravity may give rise to better crops