Legacy effects of anthropogenic disturbances modulate dynamics in the world’s coral reefs

Rapidly changing conditions alter disturbance patterns, highlighting the
need to better understand how the transition from pulse
disturbances to more persistent stress will impact ecosystem
dynamics. We conducted a global analysis of the impacts of eleven types
of disturbances on reef integrity using the rate of change of
coral cover as a measure of damage. Then, we evaluated how the
magnitude of the damage due to thermal stress, cyclones,
and diseases varied among tropical Atlantic and Indo-Pacific
reefs and whether the cumulative impact of thermal stress and
cyclones was able to modulate the responses of reefs to
future events. We found that reef damage largely depends on the
condition of a reef before a disturbance, disturbance intensity,
and biogeographic region, regardless of the type of disturbance.
Changes in coral cover after thermal stress events were largely influenced
by the cumulative stress of past disturbances and did not depend
on disturbance intensity or initial coral cover, which suggests
that an ecological memory is present within coral communities.
In contrast, the effect of cyclones (and likely other physical
impacts) was primarily modulated by the initial reef condition
and did not appear to be influenced by previous impacts. Our
findings also underscore that coral reefs can recover if
stressful conditions decrease, yet the lack of action to reduce
anthropogenic impacts and greenhouse gas emissions continues to
trigger reef degradation. We uphold that evidence-based
strategies can guide managers to make better decisions to prepare
for future disturbances.