20 | New Scientist | 29 February 2020Trees have long been at the heart
of environmental issues. Three
centuries ago, in a bid to stop local
trees being cleared, villagers in
India put themselves in front of
loggers’ axes, with some literally
hugging the trees. Several were
brutally killed, says Alice Bell
at UK climate charity Possible,
who is writing a book on the
history of climate change.The actual term “tree-hugger”
wasn’t coined until the 1960s,
though, she says, and became
pejorative in the 1970s.
Bell says the “save the trees”
movements of the 1990s and
2000s weren’t dissimilar to
today’s debate. “It was about
climate change but without
mentioning it. Now it’s climate
first,” she says.Revenge of the tree-hugger
TREE planting doesn’t usually
feature in US presidents’ speeches,
UK general election battles or the
business pitches of oil companies.
Yet in the past year, pledges to
embark on reforestation efforts
have become a popular way to
show you are committed to
fighting climate change. There
are several initiatives to plant
or protect a trillion trees, to add
to the 3 trillion we have today.
So how did we get here, with
humble tree planting taking
centre stage among the tools
to stave off extreme warming?
Can we really plant the numbers
needed to lock up enough carbonto make a difference? Perhaps
most importantly, is all this talk
of trees just a big distraction?
“Suddenly, this last year there’s
been an explosion of interest,”
says Fred Stolle at Global Forest
Watch, a US initiative from the
University of Maryland and other
groups. Rising public concerns
seem to be making governments
and corporations realise they
need to do more on climate action,
or at least be seen to do more.
“I think there’s massive
concern about climate change
now and people genuinely want
to do something about it. I think
they are reaching for what are
easy solutions,” says Joanna
House, a lead author of a UN
Intergovernmental Panel on
Climate Change (IPCC) report
on land use published last year.
Planting trees is popular,
usually uncontroversial
and brings benefits beyond
storing carbon, from our mental
well-being to habitats for wildlife.
“People love trees,” says House.The spotlight on tree planting
may have its roots in the 2015 Paris
agreement, in which governments
committed to try to hold global
temperature rises to 1.5°C, rather
than the 2°C many had expected.
This led to a 2018 IPCC report,
which made it clear that to hit
1.5°C, global greenhouse gas
emissions need to fall to net zero
by 2050. There was much debate
about “negative emissions”
technology, such as machines
to capture carbon dioxide from
the air. But with these in their
infancy, the focus fell on trees
as the only proven option.
“I think a lot of the talk around
the new ambition for 1.5°C was one
of the biggest driving forces for
putting negative emissions – and
particularly nature-based negative
emissions – on the stage,” says
Stephanie Roe at the University
of Virginia.
But tree mania accelerated last
year, when Tom Crowther at ETH
Zurich in Switzerland and his
colleagues published a paper
that said Earth has room for nearly
a billion hectares of extra trees,
which could lock up several years’
worth of humanity’s carbon
emissions. The research has been
criticised as an overestimate, but
was influential and made global
headlines. “I think that played apresident Donald Trump, who has
withdrawn the US from the Paris
agreement, backed the initiative.
But even if we start planting
vast areas tomorrow, can trees
store enough carbon to buy us
time to act on climate change?
The Crowther paper said
0.9 billion hectares could lock up
205 gigatonnes of CO 2. Including
land-use change, such as forests
being cleared for farming,
humanity’s annual emissions are
about 41 gigatonnes. But House
says many researchers were
shocked by the paper. “It’s
quite harmful because it makes
it seem like trees can do more
than they can,” she says.
Several experts took to scientific
journals to explain why they felt
it exaggerated the amount of
usable land and how much carbon
could be stored. In response,
Crowther says a lot of the criticism
is well-founded, but it is important
to get a global perspective on
what it is possible, in order to set
meaningful restoration targets.Climate changeDE AGOSTINI EDITORIAL/GETTY IMAGESNews Insight
Will trees save the world?
Everyone seems to agree that trees are a major solution to climate change,
but they can’t be the only fix, says Adam Vaughankey role in re-legitimising
reforestation,” says Mark Hirons
at the University of Oxford.
A few months later, political
parties campaigning in the run
up to the UK general election
competed on who promised to
plant the most trees. Last month
marked peak tree planting fever,
when the World Economic
Forum launched 1t.org, a plan to
plant a trillion trees (other plans
launched three years ago). Even US“ Fossil fuel industries
can say they are
harnessing nature to
address their emissions”