Climate emissions from tropical forest damage 'underestimated by a factor of six'
Scientists
say policymakers must better account for climate impacts of damage to forests,
and benefits of conserving them
Greenhouse gas
emissions caused by damage to tropical rainforests around the world
are being underestimated by a factor of six, according to a new study.
Research
led by the University of Queensland finds the climate impact of selective
logging, outright clearing and fire in tropical rainforests between 2000 and
2013 was underestimated by 6.53bn tonnes of CO2.
The
numbers are likely conservative, and also did not include emissions from other
woodlands or the massive boreal forests in the high latitudes of the northern
hemisphere.
Study
co-author professor James Watson of the University of Queensland and the
Wildlife Conservation Society
said: “We have been treating forests as pretty one-dimensional, but we know
degradation impacts carbon. The bottom line is that we knew the numbers would
be big, but we were shocked at just how big.”
Watson
said the numbers used for tropical rainforests were “conservative”, adding,
“this is a carbon time bomb and policymakers have to get to grips with this”.
When
countries declare greenhouse gas emissions from changes in forests, they do not
account for the CO2 that forests would have continued to soak up for decades
had they not been cleared or damaged. This is a measure known as “forgone
removal”.
The
study, published in the journal
Science Advances, also accounted for those emissions up to the year 2050 –
a timeframe relevant to the global Paris climate change agreement.
The
study found 6.53bn tonnes of CO2 for foregone emissions and the impacts of
other damage that wasn’t being counted.
In
comparison, for the year to March 2019, Australia’s emissions are at 538.9m
tonnes CO2e (carbon dioxide equivalent) – or 0.54bn tonnes of CO2e. Global
emissions from burning coal in 2017 were 14.6bn tonnes of CO2.
“Frankly,
inside the environment movement there has been a huge push to get a handle on
coal-based emissions, and the role of transport and airplanes. That’s
important, but the forgotten child has been forests and woodlands,” Watson
said.
The
study only counted emissions from tropical forests. In total, the world’s
forests soaked up about 28% of human-caused emissions between 2007 and 2016,
with tropical forests accounting for about half that absorption.
“We
have only looked at tropical forests and we have not looked at woodlands,”
Watson said. “We also don’t look at the boreal forests which are the biggest
game in town. Those numbers would be staggering. This story would be seriously
worse if we looked at the whole vegetation estate.
“From
a policy point of view, this is a horror story, but it also points to a simple
solution,” he said, adding that keeping forests intact and properly accounting
for the benefits would put countries like Australia at a “massive competitive
advantage”.
Lead
author Sean Maxwell of University of Queensland said: “Usually only
‘pulse’ emissions are considered – these are emissions released the instant
intact forest is destroyed. Our analysis considers all impacts such as the
effects of selective logging, forgone carbon sequestration, expanding effects
on the edges of forests and species extinction.”
Pep
Canadell of the CSIRO and the Global Carbon Project, who was not involved in
the study, said the findings were highly relevant.
“This
brings lots of pieces together to show that if our ultimate goal from
conservation was climate change, then there are many more components that we
are not taking into account in our carbon accounting,” he said. “These
researchers are calling this out.
“I
think the numbers [in the study] are reasonable. They have developed a
framework where we can better include the long-term value of the conservation
of forests for the sake of the climate.”
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