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In the clear light of a summer’s morning, a small group of entomologists
cycle into view along a rough track, carrying a mass of equipment on their
mountain bikes. They dismount and walk the last few metres to their destination,
where dozens of small polythene tents and cloches litter the ground like
jellyfish stranded on a beach. Before settling down to work, the entomologists
glance around, take out a high-powered rifle and check their ammunition.

So begins a typical day’s research on the Arctic island of Spitsbergen,
where a team of six researchers from Britain have spent the past three summers
trying to assess the likely effects of global warming on the local insects.
Because they have short life cycles, insects are sensitive ‘indicator species’:
scientists believe that changes in their distribution or abundance could
give early warning of ecological change caused by global warming. The tents
and cloches were intended to house insects, not humans, mimicking the sort
of conditions that might arise in a warmer world. And the rifle? Nothing
more sinister than the need to be prepared for encounters with polar bears,
individuals of which may be crotchety enough to attack without provocation.

Spitsbergen is the main island in Norway’s Svalbard archipelago, 650
kilometres north of the Norwegian mainland and one of the world’s most
northerly areas of land. If global warming keeps pace with predictions,
then Spitsbergen, along with other parts of the Arctic, could witness some
major changes. Forecasts of global warming vary widely, but computer models
suggest that warming will be more marked in the Arctic than in more southerly
latitudes, with temperatures rising by between 2 °C and 5 °C by
the middle of the 21st century. Hence the interest in the insect populations
of Spitsbergen.

Signs of warming are already evident in parts of Spitsbergen, says
Ian Hodkinson of Liverpool John Moores University, who is leader of the
team. ‘It’s very difficult to say from a three-year run of data, but the
general trend seems to be that the western coast of Spitsbergen certainly
is getting warmer,’ he says. ‘Last year it was very warm for quite a considerable
period early in the year – warmer than you’d expect even from the extremes
of the long-term averages.’ Climate records for the area suggest these feelings
are well founded; over the past few decades, says Hodkinson, the overall
trend in mean spring and summer temperatures has been upwards. Whether this
reflects genuine climate change or is simply part of a broad natural cycle
is not yet clear.

To take a closer look at the island’s insects, Hodkinson formed a partnership
with Jeff Bale, a biologist from the University of Bir-mingham, Bill Block
of the British Antarctic Survey, Cambridge, and Nigel Webb of the Institute
of Terrestrial Ecology, Furzebrook, at Wareham in Dorset. Two more researchers,
Steve Coulson of the University of Liverpool and Andy Strathdee of the University
of Birmingham, then joined the team. Their brief was to spend three summers
in the Arctic, taking samples and doing experiments.

Arctic outpost

In the summer of 1991, the full team flew to Spitsbergen to set up the
research project. Their destination was the northernmost ‘village’ in the
world, Ny-Alesund, where Britain’s Natural Environment Research Council
has its own laboratory. Ny-Alesund, a former mining settlement, is run by
Norway as a base for arctic research. It draws scientists from many different
countries. It has a shop, a canteen and a bar that opens only on Saturday
nights (see ‘A postcard from the world’s northernmost village’).

Privations apart, the area has enormous appeal for biologists interested
in the Arctic. Much of the terrain is ruggedly mountainous, with mighty
glaciers and huge fjords. Winter temperatures drop to – 30 °C, yet a
brief annual thaw, from June to August, allows many plants and animals
to thrive. Stunning wild flowers, such as mountain avens and purple saxifrage,
decorate the landscape.

In summer, the weather is reminiscent of a cold crisp January day in
Britain, with a temperature of about 5 °C, but with the added bonus
of constant daylight. Although this plays havoc with the body’s clock,
it does allow researchers to work in the field for long uninterrupted periods.
Another key factor in Spitsbergen’s appeal is its accessibility. If you
choose your flights carefully and the weather is right, you can leave Britain
on a Sunday afternoon, arrive at Longyearbyen, the main settlement on Spitsbergen,
just after midnight and then catch a flight up to Ny-Alesund the next morning.

Once the team had assembled at Ny-Alesund, its first task was to find
the dominant characters among the fauna. It soon emerged that the main herbivorous
insect in the area is an aphid, which lives by sucking the sap from plants
of just one species, mountain avens. Below ground, in the soil, the researchers
found a host of springtails (wingless insects) and mites (not insects, but
cousins of the spiders). All around the world, springtails and mites play
a key part in soils, helping to break down dead plants and release vital
nutrients. Even in the Arctic they live at densities as high as 100 000
per square metre.

Having made the acquaintance of these fauna, the team began their experiments.
One strand of the research involved warming small patches of ground artificially
and seeing how insect populations responded. Warming the Arctic is neither
as ambitious nor as difficult as it sounds. The team borrowed a familiar
horticultural technique and erected small polythene tents and cloches on
their study sites, supplying water as needed to match natural rainfall.
Inside these shelters, the temperature was up to 5 °C higher than it
was outside – a reasonable simulation of what might happen as a result of
global warming. Below ground, the warming effect was more modest, with soil
temperatures rising by about 2 °C. This was partly because plants growing
on the soil acted as insulation, and partly because of the cooling influence
of the underlying permafrost.

The cloches had some extraordinary effects on the aphids: they matured
earlier and laid many more eggs than usual. This increase in productivity
was so marked that by the end of the summer, heated areas contained 11 times
more aphid eggs than unheated areas. The aphids’ food plant also did better
under the cloches, as any gardener would have predicted, creating ideal
conditions for the insects living among its foliage.

Here was a phenomenon of major importance: an eleven-fold increase in
the number of eggs laid by the main insect herbivore in the area. How did
the aphid perform that impressive feat? The team found that it has a unique
life cycle that helps it to exploit its harsh, uncertain habitat. The life
cycle has two key properties (see ‘Some like it hot’). First, it ensures
that some eggs are produced in any year, provided that the weather is not
extremely severe. Secondly, it includes a mechanism for boosting the number
of sexually active adults in warm years. The researchers’ cloches allowed
this heat-sensitive ‘amplifier’ to switch on, leading to a massive baby
boom among the aphids.

All that extra fecundity would be wasted if winter cold killed the eggs
while they were waiting to hatch. But the Spitsbergen aphid is made of sterner
stuff. Its eggs are extraordinarily tolerant of cold, surviving at temperatures
of -27 °C for at least a month. What seems to control the aphid population
on Spitsbergen is the amount of warmth it receives in summer. ‘Winter conditions
do not limit its distribution,’ says Bale, ‘but summer conditions do – and
that’s rather unusual for a polar insect.’ In line with this idea, the aphid
does better on patches of ground that lose their snow cover early in the
summer and so receive more of the sun’s precious warmth.

The team decided to try to obtain a more precise estimate of the aphid’s
need for summer warmth. Ecologists gauge the amount of warmth available
in summer by calculating a measure of warmth in ‘day degrees above zero’.
This measure keeps track of both temperature and time, so two days at 5
°C, or five days at 2 °C, would each count as 10 day degrees above
zero. The team found that the aphid needs a minimum of 470 day degrees above
zero to complete its normal life cycle. If a population finds itself in
an area that cannot muster that quota of warmth, then it will die out there.

If, on the other hand, the population of aphids manages to accumulate
710 or more day degrees above zero, then its warm-weather mechanism comes
into play and it produces a profusion of eggs. After looking back through
climate records for the areas around Ny-Alesund, the team estimates that
in only one year out of the past 23 did the aphids enjoy a truly outstanding
season. But if the average temperature had been just 2 degrees higher over
that period, 20 of the 23 years would have been boom years. The aphid, it
seems, is ideally placed to exploit warm summers. ‘It’s almost preadapted
for global warming,’ says Bale.

What will happen to the aphid if global warming does keep pace with
predictions? ‘Whereas at the moment the aphid’s distribution within any
area is quite patchy,’ says Strathdee, ‘I think it’s going to spread and
invade new areas.’ The mountain avens will be overrun by a burgeoning population
of aphids drawing sustenance from its sap. ‘Within this interaction, there
is going to be a winner and a loser, I suspect,’ says Bale. Before the researchers
make firm predictions, they need to know how the aphid’s enemies, a parasitic
wasp and a predatory hover fly grub, will respond to the more generous banquet
of aphids that global warming looks likely to provide.

While the team was piecing together this story, it was doing similar
tests to see how warming would affect life below ground – the province of
the soil mites and springtails. They found that the response of these creatures
was decidedly muted. Throughout the three years of the experiment, the
researchers detected no significant difference between populations of mites
inside and outside the polythene tents. There was no surge in numbers, no
sign of any population obviously just waiting for warmth to expand enormously.

What could explain this failure to respond? Mites and other soil animals
have longer life cycles than creatures such as aphids; three years of added
warmth may simply not be enough to disturb the equilibrium of mite popu-lations.
‘We tend to think three years is a long period,’ says Hodkinson, ‘but I
suspect that three years isn’t very long for organisms which have extended
life cycles and are active for a very short period of the year.’

For much of the experiment, the spring-tails behaved much as the mites
were doing, but their story ends with an intriguing twist. In the researchers’
very last sample from 1993, a curious effect has appeared. ‘Whereas you
might expect the numbers to go up inside the tents, they seem to go down,’
says Coulson. How could the mild conditions inside the tents have triggered
a decline in population? The researchers believe that the decline can be
traced to a simple cause: loss of moisture from the warmer soil under the
tents. Laboratory tests show that Spits-bergen springtails do badly in dry
surroundings, especially when temperatures begin to climb. They collapse
and die at 30 °C in dry conditions. The mites, on the other hand, are
more resilient. They can survive an hour at temperatures well above 40 °C,
and it makes no difference to them whether they are wet or dry.

Heat endurance

This extraordinary tolerance of heat makes sound sense, even in arctic
insects. ‘It’s not unreasonable when you think of the heat they might have
to endure in the upper layers of the soil,’ explains Webb. In the Arctic,
temperatures in sheltered nooks in plant litter, for instance, can rise
to about 25 °C on a sunny day, and they would presumably rise even further
in a world made warmer by climate change. Both the mites and springtails
should be able to withstand that increase, say the researchers, provided
the soil remains moist. But if the soil were to become drier, then some
of the springtails would find life increasingly hard.

The point shows how vital it is to take into account all the relevant
factors – rainfall, for instance, as well as temperature – in any attempt
to forecast the impact of global warming on an ecosystem. A study lasting
three years, the blink of an eye in ecological terms, cannot hope to map
out all the important interactions. But the story of how Spitsbergen’s insects
respond to warmth offers a good starting point.

On one side stands the aphid, with its swift and spectacular response.
On the other, the mites and moisture-loving springtails, which seem as phlegmatic
as the aphid is mercurial. Those diverse reactions could not have been predicted
in advance, for they depend on the sort of biological details that emerge
only after painstaking field research. This is a reminder, says Block, of
how important it is to study each species in its own right rather than make
generalisations about the likely impact of global warming on insect populations
per se. ‘There are no short cuts in ecology.’

Stephen Young is a freelance writer.

* * *

Some like it hot

The main plant-eating insect at Ny-Alesund, on the Arctic island of
Spitsbergen, is the aphid Acy-rthosiphon svalbardicum. Aphids are formidable
insects – as gardeners who face plagues ofgreen fly or blackfly can readily
confirm – and the Spitsbergen species is no exception. The secret of its
success is an extraordinary life cycle, which sets it apart from its relatives
and could make it an early beneficiary of global warming.

The life cycles of aphids from more southerly areas, such as Britain,
are themselves pretty spectacular. In spring, the eggs hatch, producing
a generation of founding females (fundatrices), which produce daughters
by virgin birth. The daughters carry on the line, reproducing in the same
prolific, male-free fashion until a signal from the environment – dwindling
day length or a drop in temperature – tells them that autumn is upon them.
Then they switch to making sexually active males and females, which mate
and produce eggs that will survive the winter and start the whole process
off again inspring.

The Spitsbergen aphid, faced with an all-too-brief summer, has deftly
adapted this life cycle to its own needs. When the fundatrices mature, they
give birth to sexually active sons and daughters. Production of sexual forms
is not environmentally driven as it is in other aphids; it is decreed in
advance by the aphid’s genes. This strategy is the best way of making sure
that at least some eggs are produced during a short, cool summer lasting
no more than nine weeks.

But the Spitsbergen aphid has another trick up its sleeve, a characteristic
that means it can take advantage of warm years. As well as producing sexually
active sons and daughters, the fundatrices give birth to daughters that
can reproduce without sex. When these celibate daughters reach maturity,
they produce a second cadre of males and females. These sexual forms breed
in their own right and add to the summer’s tally of eggs. Often the weather
is too bad for this ploy to work, but when it does, the result is an extraordinary
baby boom. Global warming to the tune of 2 to 3 °C would make nearly
every year a boom year for this species – and might lead to all manner of
knock-on effects on the ecology of the area.

* * *

A postcard from the world’s northernmost village

According to the record books, Ny-Alesund (latitude 79 degrees North)
on the island of Spitsbergen is the northern-most village in the world.
A Norwegian state-owned company, the Kings Bay Kull Company, mined coal
there until November 1962, when 21 miners were killed in an explosion.
A commission of inquiry into the cause of the tragedy – not the first at
the mine – concluded that safety standards had not been properly observed.
The political fallout brought down the government of the day under Prime
Minister Einar Gerhardsen.

The company now runs Ny-Alesund as an international research centre.
All the main buildings have been turned into living quarters and laboratories
for visitors. The company provides a canteen, a shop and a bar on Saturday
nights, for around a hundred residents at the height of summer. Some technicians
and scientists of the Norwegian Polar Research Institute stay at Ny-Alesund
over winter.

A few years ago, Norway invited Britain to come and work at Spitsbergen
in any area of science. One consequence was that Britain’s Natural Environment
Research Council (NERC) leased a laboratory there as a base for its Special
Topic Programme in Arctic Terrestrial Ecology. The programme received funding
of just under £1 million and included five major projects on the
effects of temperature on arctic ecosystems, one of which took insects
as its focus. Other projects concentrated on the effects of temperature
on arctic plants.

Researchers are not the only visitors to Ny-Alesund. Spitsbergen is
inaccessible by sea in winter, but large liners dock at Ny-Alesund in
summer and discharge hundreds of visitors onto the island. These visitors
wander around the settlement and visit the post office, where they can
send postcards and letters stamped ‘The northernmost community in the world’.
Norwegian civil servants and politicians also visit Ny-Alesund to attend
a special course about Spitsbergen. Norwegian ecology students go there
to learn about arctic ecology. One house in Ny-Alesund serves as a base
for Norwegian artists.

Spitsbergen is a wild and beautiful place to work – for artists and
scientists alike. ‘The light in the Arctic is very unusual,’ says Coulson,
‘it’s very clear and bright.’ The wildlife in the area is also spectacular,
with huge numbers of breeding birds, such as barnacle geese, little auks,
guillemots, puffins and eider ducks. The seas around the island offer sightings
of seals, walruses and whales. Spitsbergen also has a population of polar
bears.

The presence of polar bears meant that the researchers were obliged
to carry a high-powered rifle with them each day as they went out to their
field sites. ‘The great danger when you’re walking in the field,’ says Block,
‘is that you’ll disturb one unexpectedly. They’ll attack you if they’re
scared. It’s part of the NERC code of conduct that you have to work in
pairs and take a rifle with ammunition. We all had to go on a training
course to use firearms of this kind.’ In the event, the gun stayed unfired,
although polar bears did visit the area from time to time. Nature’s interference
with science was limited to arctic foxes sniffing around backpacks, looking
for researchers’ lunch boxes.