New Scientist - 29.02.2020

29 February 2020 | New Scientist | 21

“In developing countries, people

very much understand the value

of trees,” he says, but only when

they play a role in deciding when

and where they are planted.

Hirons fears that the urgency

of tackling climate change

could see the wishes of local

communities being ignored.

“I think there’s a massive risk

of social harm being caused by

widespread reforestation. There

is an idea that there is lots of

underused land, which is a myth.”

While there are international

guidelines on how best to do

reforestation, set by the Society

for Ecological Restoration, there

is no requirement to follow them.

Lastly, if the CO 2 locked

away is to be counted properly, we

will need to monitor reforestation

for a long time. That is surprisingly

tricky. Deforestation is easy to

spot – satellites show areas

turning from green to brown.

But they find it hard to detect

new trees, which for the first few

years will be tiny saplings hard

to discern from space. Higher

resolution images may help.

Perhaps the biggest thing

missing from today’s focus on

reforestation is the great number

of trees being lost to deforestation,

which is getting worse. The world

lost forests the size of the UK every

year between 2014 and 2018.

Deforestation in the Amazon

rainforest has spiralled to the

highest level in a decade. Recent

bushfires in Australia burned

64,000 square kilometres in

Victoria and New South Wales,

most of it forests.

“It’s an eternal debate,” says

Stolle. “Is [reforestation] a

distraction because we really

need to stop deforestation? On the

other hand, if you look at the IPCC,

we need those negative emissions.

We can’t wait until we’ve done one

before we do the other.” ❚

planted at the right place and time.

As well as picking suitable species

for the climate and the soil where

they are planted, it will be crucial

to plant trees that help rather than

hinder biodiversity.

Biodiversity warning

Take the UK, where the

government’s climate advisers

have called for a tripling of tree

planting to hit carbon goals. Jane

Memmott at the British Ecological

Society says there are huge

differences in biodiversity levels

between trees you might pick

for the UK. “Something like oak

and birch is fantastic – there are

literally hundreds of species

associated with them, whereas

something like sycamore

has pretty much a single aphid

on it,” she says.

Then there are the people who

live in and around the places

where reforestation might

take place, often in developing

countries. Restored forests

won’t thrive or remain intact

long enough to lock up CO 2 for

centuries if local people aren’t

invested in them, says Stolle.

New forests could
lock up large amounts
of carbon dioxide

Based on Roe’s review of the
literature, reforestation has the
potential to lock up between
1 and 10 gigatonnes of CO 2 a year.
“In terms of what is feasible,
we came to 3 to 4 gigatonnes
[a year],” she says.
More research is under way on
calculating the carbon storage
potential of tree planting. In the
meantime, it seems large enough
to be attracting big business.
Last year, Shell announced that
it would spend $300 million
over three years on reforestation
projects to generate carbon
credits for itself and others.
On Crowther’s analysis, Duncan
van Bergen at Shell says: “Even
those people who have challenged
it, have not challenged the fact
that it is really, really big. It’s on
the margins between really big
and huge.” He says the numbers
presented “resonated” with
Shell’s own researchers.
Such interest in reforestation
from oil companies has set alarm
bells ringing in some quarters.
“Fossil-fuel industries can say
they’re harnessing nature to
address their emissions, which is
dubious I think, in terms of the
scientific case for this significantly
having an impact on climate
change,” says Hirons.
There is a risk that we plant
trillions of trees without firms
and countries also deeply cutting
their emissions. Shell says that
isn’t the case. “We are definitely
not doing this instead of other
tough things and changes we
need to make. This very much
comes on top,” says van Bergen.
Even if mass reforestation
happens in parallel with
decarbonisation of economies,
Stolle warns that trees must be

▲ Phobos

Japan’s space agency

has announced plans to

send a probe to Mars’s

potato-like moon, Phobos,

and bring back a sample.

▲ Pony rescue

A pony trapped in a hole

in Flintshire, UK, was

rescued with the help

of a mechanical digger.

▼ Bitcoin

Crime didn’t pay for a

drug dealer who lost

£46 million in bitcoin

after storing his access

codes in the cap of a

now-missing fishing rod.

▼ Burger King

In an effort to trumpet

its removal of artificial

preservatives, the fast

food giant has released a

video of a Whopper burger

growing mould. I’m loving

it! No, that’s the other one.

▼ Te s la

Hackers tricked a Tesla

into breaking a speed

limit by using black tape

to make a 35 mph sign

look like an 85 mph one.

Still, they do have very

good acceleration.

Working

hypothesis

Sorting the week’s

supernovae from

the absolute zeros

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There are multiple efforts

under way to plant

a trillion more trees

DOUGLAS GIMESY/GETTY IMAGES BOTTOM: TESLA; TOP: NASA