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 thanplant 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 climatechange 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 limitedexperience 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