The Economist

The EconomistAugust 4th 2018 Science and technology 65

2 pairs of counter-rotating “horizontal roll”
fire vortices that form in mid-air but can
collapse onto the ground; and “flame fin-
gers” that have smitten firefighters even
100 metres from a fire’s edge.
The most extreme 1% or so of wildfires
however are likely to remainunmodella-
ble for some time. These include the “ex-
plosive” wildfires that ravaged central Por-
tugal last year. On June 17th 2017 wildfires
broke out around Pedrógão Grande near
Coimbra. Initially meteorologists reck-
oned that these fires would advance at
about 3kph but the soaring flames soon
changed direction and accelerated to six
times that speed. Sixty-seven people died
nearly half of them trapped motorists.
Flames that rose roughly 100 metres
into the sky during these fires generated a
gale and searing “pyrocumulus” clouds a
process too complex for today’s best soft-
ware to model according to Marc Castell-
nou a member of the technical commis-
sion that studied the disaster. Francisco
Castro Rego an expert on fire forecasting at
the University of Lisbon reckons that at
least two more years of development will
be needed to model such fires.
Fire-modelling is however getting bet-
ter all the time. New satellites with short-
wave-infrared sensors can detect fires as
small as a backyard barbecue. Satellites
and aircraft with rangefinders that use li-
dar an optical version of radar can map
the height of vegetation precisely which
helps forecasting software work out
whether a brush fire is likely to ignite trees.
As statistics on fires accumulate new cor-
relations will be identified such as how
fluctuations in average temperature influ-
ence burn sizes on a given landscape. Such
intelligence will be needed increasingly in
the future. Predictions based on the likely
effects of climate change suggest that by
the middle of the century fires will burn
twice as much acreage as they do today. 7

A twisty-turny thing

“A

T THE end of the day I would be anx-

ious” says Anil Awasthi a 44-year-

old garment worker in Delhi “thinking

what mistakes of mine would be pointed

out.” He was worried about what was go-

ing to happen as his sight deteriorated un-

til—courtesy of VisionSpring an American

social enterprise—he got reading glasses.

“I’m confident now that my work will

meet my boss’s expectations” he says. “I

go home satisfied.”

For the rich the worst consequence of

long sightedness is having to wear the

world’s most ageing accessory. For the

poor things are more serious. “It’s the 42-

year-old seamstress or tailor” says Jordan

Kassalow VisionSpring’s founder. “If they

can’t see they can’t do their jobs and if

they can’t do their jobs they end up break-

ing rocks by the side of the road.”

The first randomised control trial to

measure the impact on productivity of

reading glasses was carried out recently in

a tea estate inAssam innorth-eastern In-

dia paid for by Clearly a charity. Nathan

Congdon a professor of ophthalmology at

Queen’s University Belfast and his col-

leagues gave spectacles to half of a group

of 751 tea-pickers aged over 40. The other

half got none. Over11weeks the productiv-

ity of those whose sight had been cor-

rected rose by 39%. It rose for the others

too showing the importance in such trials

of having a control group. But that rise was

only 18%. The rise in productivity for those

with glasses was the largest caused by a

medical intervention that has ever been

shown in such a trial (others have been of

mosquito nets and micronutrients). Since

tea-picking is piecework productivity

translates directly into money.

Before Dr Congdon’s trial none of the

751 had worn glasses. Given the potential

gain in income and the cheapness and

simplicity of spectacles that seems odd. It

is not however unusual. Some 1.1bn peo-

ple suffer from uncorrected long sight. In

this as in many areas of health both gov-

ernments and the market fail the poor.

Poverty is one explanation. Liberia

says Dr Congdon has but two eye doctors

both in the capital. Even in China which is

far better-served half of those with poor

sight do not have the glasses they need.

There are social issues: some people worry

that spectacles make them look ugly. There

are regulatory hurdles too. In some coun-

tries only licensed operators may sell

glasses so hardly anybody does. And be-

cause long sight creeps up on people vic-

tims get used to it: “They probably thought

‘you get to 50 you can’t pick like you used

to’” says Dr Congdon of the tea-pickers.

“But by the end of the trial their productiv-

ity was as good asthe youngsters’.”

VisionSpring is trying to nudge the mar-

ket to work better by using the “Avon-lady”

model. It introduces middle-aged women

to glasses then provides them with the

wherewithal to sell them door-to-door.

That idea is spreading slowly but clear

sight is a surprisingly hard sell. 7

Long sightedness

I can see clearly

now

Wear glasses. Earn more

Looking to the future