LESSONS FROM CORAL REEF DEVASTATION, REORGANISATION, AND RECOVERY - PDF document

LESSONS FROM CORAL REEF DEVASTATION, REORGANISATION, AND RECOVERY Nick Graham @naj_graham www.lec-reefs.org Early reef species existed with the dinosaurs Williams & Graham (2019) Func Ecol 1

Uncertain futures in the Anthropocene Williams & Graham (2019) Func Ecol Coral Bleaching 2

BLEAK TIMES! “Roughly half of the corals on the #GreatBarrierReef died in the past 18 months (from global warming).” Greg Torda Terry Hughes … and of course it wasn’t just the GBR Fiji Japan Maldives Seychelles 3

Hughes et al. 2018 Science 4

Change in coral cover through 1998 Graham et al. PLOS ONE 2008 5

REEF TRAJECTORIES FOLLOWING MAJOR BLEACHING Recovery versus regime shifts RECOVERY (12 sites) Graham et al. 2015 Nature REGIME SHIFT (9 sites) 6

Recovery versus regime shifts RECOVERY (12 sites) Graham et al. 2015 Nature REGIME SHIFT (9 sites) Novel fish communities Robinson et al. 2019 Global Change Biol 7

Boom and bust of keystone structure Bleaching Bleaching Massive coral Branching coral Total coral Branching coral loss in 2016 Branching coral recovery post-1998 1994 2005 2008 2011 2014 2017 Wilson et al. 2019 Coral Reefs Depth PREDICTORS OF RECOVERY Rugosity Nutrients Graham et al. 2015 Nature Herbivore Juvenile biomass coral density 8

Nutrient pollution and fishing are pervasive Hughes et al. 2010 TREE MacNeil et al. 2015 Nature NUTRIENTS 9

Coral cover dynamics on the GBR MacNeil et al. Nature Eco Evo 2019 Acropora cover dynamics on the GBR MacNeil et al. Nature Eco Evo 2019 10

Water quality mediates coral recovery on the GBR  17% improvement in catchment water quality would enable many reefs to recover between bleaching events to 2050 MacNeil et al. in review Not all nutrients are bad High nitrogen, low High nitrogen AND phosphorus phosphorus  Slower growth  Bleaches easier  Faster growth  Bleaches at higher threshold D’Angelo & Wiedenmann 2014 Curr Opin Env Sust 11

Corals feed more in naturally nutrient rich waters Fox et al. Curr Biol 2018 12

INVASIVE RATS Seabirds bring nutrients from open ocean 13

Seabirds & nutrients higher on rat-free islands Graham et al. 2018 Nature Huge nutrient subsidy Graham et al. 2018 Nature 14

Huge nutrient subsidy Graham et al. 2018 Nature Fish aged and growth assessed using otoliths 15

Fish grow faster with seabird nutrient subsidies Graham et al. 2018 Nature UNDERWATER SURVEYS OF FISH COMMUNITIES AT EACH ISLAND 16

Fish biomass higher with seabird nutrient subsidy Graham et al. 2018 Nature Fish biomass higher with seabird nutrient subsidy 47% higher total fish biomass Graham et al. 2018 Nature 17

Coral bleaching CORAL BLEACHING Shifts to calcifying algae next to seabird islands Benkwitt, Wilson & Graham GCB (2019) 18

Seabird nutrient enhance coral growth FOUR times !! Savage 2009 Sci Reports FISHING 19

Fisheries following coral loss James Robinson CPUE Robinson et al. Nature Eco Evo (2019) Ecology alone is far from enough 20

Marrying social and ecological systems Kittinger et al. 2012 Ecology & Society Underlying social drivers of change Hicks et al. 2016 Frontiers Ecol & Environ 21

Gear-based management More gears restricted Protected areas McClanahan et al. 2015 Cons Bio CORAL REEFS ARE CHANGING  Implications for algal dominated systems, biodiversity, and changing fisheries compositions  Reducing terrestrial nutrient pollution will be essential for some reef systems to recover  Not all nutrients are bad, and natural flows should be re-instated  Diverse approaches to ecosystem-based fisheries management should be explored 22

Thank You ! 23