5 October 2019 | New Scientist | 37region-dependent estimates for biomass.
The new sensors will provide accurate
measures, putting the project on a more
empirical footing.
Worldwide, some 15 billion trees are felled
each year – and more than 3 trillion have been
cut down since people began farming around
10,000 years ago. Now, increasing urbanisation
means there is great potential for reversing
this trend. Indeed, research published in July
reveals that Earth could support enough
additional trees to cut atmospheric carbon
levels by 25 per cent – making this by far the
best climate change solution available. Some
big reforestation projects are already under
way. China, for example, has planted an area
a quarter of the size of the Amazon rainforest
in the past two decades. With the new wave
of remote sensors, we will be able to measure
the success of such projects, and their impact
on efforts to keep global warming in check.
That truly will be a giant leap for humanity. ❚Christine Swanson is a
freelance writer based
in Gainesville, Florida©FER
DINANDOSCIANNA/M
AGNUM^ PHOTO
S^Restoring ecosystems could be
a crucial weapon in our efforts
to avoid climate catastrophe.
By drawing carbon out of the
atmosphere, plants lock away the
greenhouse gases that cause global
warming. Reforestation offers the
greatest potential because trees
contain so much carbon, and
historic deforestation means there
are large areas of land that could
be restored to woodland. Coastal
habitats offer a similar opportunity- the available area may be less, but
the carbon payback is even greater.
Lined with mangroves, salt
marshes and seagrass meadows,
coastal ecosystems are repositories
of “blue carbon”. While forests hold
most of their carbon within woody
biomass, coastal plants pull carbon
out of the air and water and channel
it through their roots deep into the
ground – burying it indefinitely,
provided the system stays healthy.
As a result, coastal plants can
absorb many times more carbon
than trees covering the same area.
A seagrass meadow, for example,
contains anywhere from 10 to 40
times as much, 95 per cent of which
is stored in sediment. The problem
is, these aquatic ecosystems are
disappearing. Mangroves and salt
marshes are often removed to make
way for coastal developments, and
seagrasses are dying as pollution
depletes oxygen levels in coastal
waters. It is estimated that
approximately one third of blue
carbon sinks have already vanished.
Concerted efforts are being made
to restore coastal ecosystems. One
of the longest-running projects is in
Chesapeake Bay on the east coast
of the US, where seagrass meadowsincreased by 8 per cent last year.
Now, researchers at the University
of Southern Denmark are trying to
work out the best way to cultivate
seagrass. Unlike seaweeds,
seagrasses are vascular plants with
roots and flowers, so can be sown
from seeds or planted as seedlings.
The team tested various cultivation
methods and found that planting
seedlings was most successful
because shifting shorelines and
sediment accretion made it hard
for seeds to get established.
They want to see their techniques
adopted on a massive scale. They
point out that seagrasses have the
potential to grow in coastal waters
all over the world, except Antarctica.
So blue carbon sinks could play
a significant part in efforts to curb
global warming – not to mention
beautifying our coastlines.Turning carbon blue
in California turned countless trees to ash,
sending their stored carbon literally up in
smoke. Such dramatic events are likely to
become more common as the world gets
hotter. In future, with an array of remote
sensors, we will be able to properly assess
the damage they have done. We will get a
more accurate measure of how much forest
is being lost through logging, too, because
the new generation of imagers will be able
to detect the thinning out of woodland as
well as the entire clearance of patches that
conventional imagers can see.
Remote sensors also have the potential
to aid forest protection and regeneration.
The 2015 Paris climate agreement included
a programme called REDD+, designed to help
poorer countries keep their forests intact
by offering financial incentives to reduce
carbon emissions caused by deforestation
and degradation. “For REDD+ to work, it is
crucial for people to be able to accurately and
reliably monitor how much carbon emissions
have happened,” says Jonah Busch, chief
economist at the Earth Innovation Institute.
To do that, they first need to know how much
carbon is contained in their forests. At present,
this is estimated using satellite images andbasis to build a better understanding of tree
mortality and regrowth.
There are other projects on the drawing
board, too. These include the NISAR mission,
the first radar imaging satellite to use dual
wavelengths, which is due to launch in 2021.
A collaboration between NASA and the Indian
Space Research Organisation, it is designed
to observe and measure a range of natural
processes including tsunamis, earthquakes,
ice-sheet collapse and ecosystem disturbances.
Together with satellites already in orbit,
information from GEDI, Biomass, NISAR
and more will be combined to give the first
wall-to-wall picture of the world’s forests.
“Collaboration does seem to be quite a unique
component of what’s happening with the
biomass missions,” says John Armston at the
University of Maryland, who works on GEDI.
All this means that in a few years, we will
have a much better idea of where the missing
carbon is going – or at least how much of it
is being taken up by trees. The new satellites
will also help reveal the varying exchange of
carbon between trees and the atmosphere.
Last year, for example, the hurricanes that
hit the southern and eastern US felled vast
swathes of forest, while wildfires that raged