Page 31 - Science

RESILIENCE

about how to catalyze such recovery Coral resilience systematic resilience and avoid cas-
processes is important. However, if With shrinking recovery windows between bleaching events, future cading failures across reef systems.
climate change continues unabated, resilience may come not from the ability of corals to recover, but from On a global scale, are a few ref-
resilience may come not from the their ability to resist the impacts of climate change. uges enough? The fossil record
ability of coral reefs to recover but shows repeatedly that after histori-
from their ability to resist. Intrinsic resistance Extrinsic resistance cal mass extinction events, small,
The idea of protecting resistant Natural “super coral” traits could Deeper reefs and colder waters isolated, and ephemeral refuges
species or resistant areas is not new, underpin new technologies. might provide refuges for corals. protected critical remnant popula-
but for various reasons, it is not of- tions that seeded recovery and were
ten put into practice. To increase crucial for the persistence of biodi-
ecosystem resistance to climate versity (13). On contemporary coral
change, there are two options: to in- reefs, even small areas of high coral
crease intrinsic resistance, provided cover can produce abundant, high-
by traits that allow species to cope quality larvae (14). Finding and
with a changing climate, or to in- protecting even the smallest of re-
crease extrinsic resistance, provided Super Coral Greater Cool sistant refuges is an urgent priority
by locations that are less vulnerable corals garden depth currents for global conservation efforts.
to climate disturbances.
Connecting survivors
Even a few small, coral-rich refuges could act as sources of adaptations WHEN RESILIENCE RUNS OUT
INTRINSIC RESISTANCE: and propagules that can seed other reefs. Whether marine ecosystems resist,
“SUPER” CORALS recover, restructure, or vanish hinges
Individuals or species that survive Sharing adaptations Bleached reef on how extreme future climate change
over long distances
extreme climate events can have is. It is almost certain that most
traits that underpin a general abil- of today’s coral reefs will be trans- Downloaded from
ity to cope or adapt to new envi- Healthy reef formed beyond recognition in the
ronmental conditions. For corals, coming decades. Shifts in coral com-
resistant traits include tolerance to Reseeding events munities toward smaller, weedier spe-
warmer and acidified waters, salin- cies and dominance by other groups,
ity fluctuations, herbicides, diseases, such as algae and sponges, will alter
and storms (4). These traits might be associ- done using a “portfolio-like” approach to ecosystem functioning and reduce the ser-
ated with aspects of the coral microbiome conservation that maximizes diversity and vices that coral reefs provide to society (15).
(5), or the ability of corals to draw on energy connectivity among populations. Protecting These ecological shifts will force millions http://science.sciencemag.org/
reserves or flexible feeding strategies (6). populations across the broadest range of en- of people to adapt and change how they use
Natural populations of “super corals” that vironments (including degraded reefs) can and depend on the fisheries, tourism, and
are tolerant of stressful conditions might provide new combinations of genotypes or coastal protection provided by coral reefs.
arise after repeated bleaching events (7) species, some of which might cope with fu- The political will necessary to improve
or in more variable thermal environments, ture climate conditions (10). the resilience of coral reefs or marine eco-
such as reefs exposed to tidal heat pulses (8). systems might or might not materialize in
A better understanding of natural super EXTRINSIC RESISTANCE: A FEW time. Regardless, any fight for the remain-
corals might lead to innovative technologies GOOD REFUGES ing “reefs of hope” can, and must, occur on March 1, 2018
of assisted gene flow and assisted evolution Cool currents and deeper reefs might be ar- alongside improving the resilience of peo-
that can help to climate-harden corals (see eas where corals can persist. Today, however, ple and communities to help dampen the
the figure). However, artificially increasing such spatial refuges are increasingly rare. coming climate shocks. j
the resistance of corals to warmer and more A case in point is the Great Barrier Reef,
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and Adaptation Program. As the options to
pre-
the
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tially beneficial technologies.
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(see the figure)
We can also help nature “pick the winners”
will not address
the
root
R. Iglesias-Prieto, Sci. Rep.3, 3486 (2013).
by preserving the raw material for natural
cause of the coral reef crisis—greenhouse
selection, i.e., genetic diversity. This can
10.1126/science.aas9852
SCIENCE sciencemag.org be gas emissions—but it is a chance to support 2 MARCH 2018 • VOL 359 ISSUE 6379 987
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