Reduced carbon emissions and fishing pressure are both necessary for equatorial coral reefs to keep up with rising seas

Abstract

A rapid increase in sea‐level rise is generating vertical accommodation space on modern coral reefs. Yet increases in sea‐surface temperatures (SSTs) are reducing the capacity of coral reefs to keep up with sea‐level rise. We use ensemble species distribution models of four coral species (Porites rus, Porites lobata, Acropora hyacinthus and Acropora digitifera) to gauge potential geographic differences in gross carbonate production. Net carbonate production was estimated by considering erosional rates of ocean acidification, increasing cyclone intensity, local pollution, fishing pressure and the projected burdens of increases in SSTs (under Representative Concentration Pathways (RCPs) 4.5, 6.0 and 8.5) through to the year 2100. Our models predict that only 4 ± 0.1% (~60 000 km2) of Indo‐Pacific coral reefs are projected to keep up with sea‐level rise by the year 2100 under RCP 8.5 – most of which will be located near the Equator. However, with drastic reductions in emissions (under RCPs 4.5 and 6.0 Wm−2), we predict that 15 ± 0.3% (~250 000 km2) (under RCP 4.5 Wm−2) and 12 ± 0.7% (~200 000 km2) (under RCP 6.0 Wm−2) of Indo‐Pacific coral reefs, have the potential to keep up with sea‐level rise by the year 2100. Yet the burdens of fishing pressure and its cascading effects are projected to be responsible for substantial reef erosion, nearly halving the number of reefs able to keep up with sea‐level rise. If action is taken immediately and emissions are drastically reduced to RCPs 4.5 or 6.0 Wm−2, and reef management reduces the burdens of local pollution and fishing pressure, then our model predicts that 21–27% (~350 000–470 000 km2) of Indo‐Pacific coral reefs – most of which will be located near the Equator – would have the potential to keep up with sea‐level rise by the year 2100.