National Geographic

1### 1Townsville``````Cairns``````Cooktown``````MackayMA### RINE^PARKGREAT^BARRIERREEF^Gulf of Carpentaria### SeaPalmIs.``````FlindersReefsHolmesReefs``````CoringaBankTregrosse ReefsMarion ReefLihou Reefs``````SwainReefs``````WhitsundayGroupCape MelvilleCape (^) FlatteryAUSTRALIANEWGUINEA(^1) , (^150)MILESGREAT BARRIER REEFMARINE PARKDIRECTIONOF VIEWSydneyBrisbaneCanberraZooxanthellaealgaeHealthy BleachedDecayStressedEnlargedat rightHeat stress in2016 killed8 0% of coralin this sectionof the reef.20142015 2016 2017Degreeheating week(DHW)combinesintensity andduration ofheat stressinto a singlenumber.Great Barrier ReefFar Northern Management AreaHEAT STRESS161284HOW HOT FOR HOW LONGAs climate change warms Earth’s oceans,underwater heat waves last longer.Coral species can’t withstand extendedhot periods. They start to die off, whichdiminishes reef diversity. After heatstress becomes severe, as it did along thenorthern Great Barrier Reef in 2016, fewspecies remain, and final die-off is rapid.NO TIME FOR RECOVERYSevere regional bleaching used to hit a given reef aboutevery 27 years. Since the 1980s, the pace has acceleratedto every six. Even in the best conditions, badly damagedreefs take at least 10 years to rebound. The Great BarrierReef, struck two years in a row, may never fully recover.A healthy partnershipAlgae feed the coral;coral provides shelter andnutrients to the algae.Relationship breakdownCoral stressed from overly hot water expelsthe algae, causing the coral to starve. Theskeleton of dying coral decays once exposed.ATLAS BY LAUREN E. JAMESREEF WATCH; ROBIN BEAMAN, JAMES COOK UNIVERSITY; AUSTRALIAN HYDROGRAPHIC OFFICE; GEOSCIENCE AUSTRALIA; AUSTRALIAN INSTITUTE OF MARINE SCIENCE; RAYBERKELMANS AND OTHERS, CORAL REEFS 23, 2004; © OPENSTREETMAP CONTRIBUTORS, AVAILABLE UNDER OPEN DATABASE LICENSE: OPENSTREETMAP.ORG/COPYRIGHT