5 February 2022 | New Scientist | 27Views
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ORAL reefs in Australia are
set to experience another
mass bleaching event due
to ocean temperature rises – the
fourth in seven years – according
to a forecast released by the US
National Oceanic and Atmospheric
Administration. Reefs need
serious efforts to help them to cope
and survive, but our endeavours
are currently misplaced, focusing
on the glamorous rather than
the effective.
Coral gardening projects, where
coral species are cultivated and
cared for by humans in floating
nurseries before being planted
back onto the reef, are popping
up around the world. While there
are some advantages to this
approach – we can choose parent
corals that are more likely to
survive warmer temperatures in
a warming ocean, for example –
it is riddled with problems.
For a start, genetics is rarely so
straightforward. The same gene
that codes for heat tolerance
might also make corals more
susceptible to a particular disease,
for instance, or more likely to
fail reproductively. Stacking the
genetic odds in the coral’s favour
in terms of heat tolerance might
not necessarily be a winning
strategy over the long term.
One of the methods used is
called fragging, in which a small
piece of coral is broken off the
parent, much like a cutting,
and grows to form a new coral.
Although it can work, it is more
like a quick fix. The resulting
MIreef can easily lack genetic
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diversity if all the “cuttings” are
genetically identical – and that
means the corals could be more
likely to perish in changing
environmental conditions.
Most coral reef gardening
projects are small, and haven’t
been running for very long. More
than two-thirds of all coral reef
restoration projects have lasted
for 18 months or less, meaning that
their long-term effects aren’t well
understood. And most projects
have been carried out over small
areas, often 100 square kilometresor less. We can’t rely on coral
gardening to save reefs over large
areas and the longer term.
All is not lost. There are actions
that will make a difference for
coral reefs and we need to
prioritise them immediately.
The first is creating and
enforcing marine protected areas.
The UN described overfishing
as “the most pervasive and
immediate” threat to reefs in its
5th Global Biodiversity Outlook
report in 2020. Coral ecosystems
rely on the marine life thatsurrounds them – coral fish faeces
contains algae that corals need to
survive, for example, and parrot
fish feed on seaweed that would
otherwise suffocate reefs.
When parts of the ocean are
completely free from human
activities that can give coral reefs
the space and the time needed to
naturally recolonise and recover
what they have lost, including
much of the genetic diversity and
biodiversity of the original reef.
But marine protected areas
aren’t enough on their own. High
ocean temperatures will result in
bleached corals even if the area is
protected. Coral reefs are likely
to decline by 50 to 90 per cent
by 2050 due to ocean warming
even if we succeed in keeping
atmospheric warming to well
below 2°C above pre-industrial
levels, as set out in the Paris
Agreement. That is why fast action
is needed now to curb fossil fuel
emissions and keep us well below
that 2°C mark.
If we truly want our coral reefs
to survive and thrive, we must
combat the source of the problem.
What reefs really need is for us
to drastically reduce our fossil
fuel emissions immediately
and protect the reef fish and
biodiversity that nourish and
sustain coral ecosystems.
Everything else is a distraction. ❚Saving the reefs
Coral gardening projects are more popular than ever, but they
are a distraction from the real solutions, says Catherine CollinsCatherine Collins is
a science journalist
based in Brussels,
Belgium