Data and code for: Dietzel et al. Long-term shifts in the colony size structure of coral populations along the Great Barrier Reef

The age or size structure of a population has a marked influence on its
demography and reproductive capacity. While declines in coral cover are
well documented, concomitant shifts in the size frequency distribution of
coral colonies are rarely measured at large spatial scales. Here we
document major shifts in the colony size structure of coral populations
along the 2,300km length of the Great Barrier Reef over the past two
decades. Coral colony abundances on reef crests and slopes have declined
sharply across all colony size classes and in all coral taxa compared to
historical baselines. Declines were particularly pronounced in the
Northern and Central regions of the Great Barrier Reef, following mass
coral bleaching in 2016 and 2017. The relative abundances of large
colonies remained relatively stable, but this apparent stability masks
steep declines in absolute abundance. The potential for recovery of older
fecund corals is uncertain given the increasing frequency and intensity of
disturbance events. The systematic decline in smaller colonies across
regions, habitats and taxa, suggests that a decline in recruitment has
further eroded the recovery potential and resilience of coral populations.