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Physical and Biological Drivers of Coral-ReefDynamics11Richard B. Aronson and William F. PrechtAbstractCoral-reef ecosystems are declining worldwide, compromising their capacity to provideecosystem services that include feeding hundreds of millions of people and protectingshorelines from erosion. The anthropogenic causes of reef degradation are complex andoperate over a broad range of scales and hierarchical levels,but accelerating climate changeand its collateral impacts are currently the strongest drivers. Deleterious trends in local-scale, ecological processes that occur within reef communities, such as declining herbivoryand increasing eutrophication, generally play a subsidiary role at present, because theireffects are overwhelmed by the impacts of climate change on many reefs. That does notmean local-scale ecology is irrelevant. Solving environmental problems at one scale orlevel will by default leave problems at the other scale as the new primary problems. Ifhumanity is able to control climate change at the global level, then community-levelprocesses will in general become limiting. Both local and global impacts must be mitigatedand reversed if we are to save coral reefs.KeywordsAcropora ? Caribbean ? Climate change ? Coral bleaching ? Coral disease ? Marine protectedareas ? MPAs ? White-band disease11.1 IntroductionMarine ecosystems throughout the world ocean have beendamaged by human activities, and coral reefs have sufferedespecially severe impacts (Halpern et al. 2008). The chal-lenge for coral-reef scientists is to determine the strongestcausal pathways to degradation. Measuring the relativecontributions of proximate and ultimate candidate-causes isnot merely an academic exercise; the prescriptions formitigating and reversing reef degradation differ dependingon the scales, hierarchical levels, and identities of thosecauses. With limited resources available to conserve coralreefs, it is imperative that time, labor, and funds be devotedto corrective measures that will yield the maximum benef i ts.Because reefs are geological as well as ecologicalentities, the physical sciences have been integral to theirstudy from the start. Our understanding of how coral reefsoperate strongly emphasizes physical drivers (e.g., Robertset al. 1992; Hubbard 1997; Montaggioni and Braithwaite2009). A few basic examples highlight the physical controlof biological processes: (1) reef development is limited tolatitudes warmer than the 18? C winter-minimum isotherm(Dana 1843; Johannes et al. 1983; Kleypas et al. 2001);(2) upwelling driven by oceanic gyres restricts reef develop-ment off the west coasts of continents (Birkeland 1997;Hubbard 1997), and inimical waters suppress reefR.B. Aronson ( * )Department of Biological Sciences, Florida Institute of Technology,150 West University Boulevard, Melbourne, FL 32951, USAe-mail: raronson@f i t.eduW.F. PrechtDivision of Marine and Coastal Programs, Dial Cordy and Associates,Inc., Miami, FL 33014, USAe-mail: william.precht@gmail.com# Springer Science+Business Media Dordrecht 2016D.K. Hubbard et al. (eds.), Coral Reefs at the Crossroads,Coral Reefs of the World 6, DOI 10.1007/978-94-017-7567-0_11261