New Scientist - 02.18.2020

26 | New Scientist | 8 February 2020

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Editor’s pick

More common ground

on the changes we need

Letters, 21/28 December 2019

From Iain Climie,

Whitchurch, Hampshire, UK

Roger Taylor notes that recycling is

one area where common ground

can be found with climate change

sceptics. There are many more.

Restoring fish stocks, reducing

waste, combining conservation with

careful usage, using alternatives to

fossil fuels, making less use of cash

crops, promoting tree growth and

use via silviculture and cutting the

impact per head of livestock and

their overall numbers are examples.

Maddeningly, politicians and

other policymakers could have

supported these actions in the past

30 to 40 years, since they make

sense whether climate change

develops as expected or not – and

even if temperatures fall following

a major volcanic eruption. Further,

trees can be good near-term carbon

sinks, are a potential source of fuel

and have other benefits. As usual,

short-termism won out over

intelligent win-win policies.

Can planting trees combat

climate change very much?

Letters, 7 December 2019

From James Fenton,

Clachan Seil, Argyll, UK

Recent letters, like that from

Adam Osen, focus on planting

trees to help mitigate climate

change through their storage of

carbon. It may not always work.

Planting trees on open ground

may change the reflectivity, or

albedo, of land. At higher latitudes

this can cause a warming effect,

as three-dimensional woodland

absorbs more radiation than the

essentially two-dimensional

open ground that it replaces.

In many places new planting

is likely to be targeted at upland

areas, which generally possess

stratified soils with a high organic

carbon content. In the UK there

is an order of magnitude more

carbon stored in soil carbon than

plant biomass. Tree planting on

such soils can oxidise this carbon,

potentially releasing more than

the amount taken up by the trees.

And practices such as ploughing

land before planting can dry out

the soil, causing carbon release. At

the other end of the forestry cycle,

modern tree extracting machines

can similarly churn up the soil.

So it isn’t clear to me whether

tree planting will benefit the

climate. There is also the issue of

natural and semi-natural habitats

being converted to woodland at

the expense of biodiversity.

I believe the best approach

would be to leave the extensive

tracts of UK upland with a shallow

humus layer unplanted, so that

over time the soil carbon store

builds up and, on level ground

at least, goes on to form peat.

Reforesting is a stopgap

solution to carbon woes

11 January, p 44

From Martin Murray,

Telford, Shropshire, UK

I appreciate Tom Crowther’s

research on reforestation, which is

vital and urgent. But reforestation

is a stopgap solution to climate

change while we decarbonise the

economy. What if we plant enough

trees to stabilise carbon dioxide

levels in the air, while still burning

fossil fuels? We would end up with

a planet that is still warming and

has nowhere left for new forests.

Forest restoration is essential –

and will help with maintaining

biodiversity. But it must be done

alongside emissions reductions.

An obstacle to making

deniers my friends

11 January, p 21

From Guy Cox, St Albans,

New South Wales, Australia

David Westmoreland and Connor

McCormick say the flat-Earthers

they meet are savvy about science.

They also report flat-Earthers

measuring shadow lengths at

various latitudes to look for

curvature of Earth and coming

up with inconclusive results.

The African-Greek scholar

Eratosthenes used this method to

calculate Earth’s circumference

before 200 BC. He was correct to

within 10 per cent. So much for

the flat-Earthers’ experimental

competence. There may be

another explanation. My limited

experience of such people leads

me to think that many are just

contrarians who enjoy the

challenge, doubtless honed in

school debating societies, of

defending the indefensible.

Just when an autonomous

car needs you most...

Letters, 18 January

From Anna Zee, Leicester, UK

Will motion sickness be an issue

for people deprived of a sense of

control in autonomous cars, asks

Frank Siegrist. It will. I first heard

of this in 2018, at a conference on

highly automated vehicles at the

University of Warwick, UK. Before

we reach full vehicle autonomy,

human drivers will need to take

over in some circumstances. There

is currently, as I understand it, no

way of determining whether a

driver may be impaired by motion

sickness when required to do this.

Reasons why Neanderthals

may not have died out

7 December 2019, p 19

From Roger Williams,

Lucerne, Switzerland

You report philosopher Krist