Source: CO2 Science
In introducing their newest study of the subject, Cramer et al. (2012) write that “Caribbean reef corals did not appear to be affected by human activities until the 1980s (Hughes, 1994),” but they say that “since this period, coral cover in the Caribbean has declined by an average of 80% (Gardner et al., 2003) and branching species of Acropora and Poritescorals have been replaced by non-branching species of Agaricia and Porites,” citing Aronson et al. (2004, 2005) and Green et al. (2008). They also indicate that “surveys of fossil reefs have revealed that such drastic changes in Caribbean coral communities are unprecedented over the last c. 200,000 years despite large fluctuations in sea level and climate (Pandolfi and Jackson, 2006; Greer et al., 2009), implicating [some non-climatic] anthropogenic disturbance in the recent decline.” Nevertheless, they write that “the appearance and intensification of mass coral disease and bleaching events in the Caribbean and elsewhere have been widely attributed to anthropogenic climate change.”
So what, or who, is the real culprit? And how was the guilty party identified?
In terms of their contribution to the search effort, Cramer et al. “analyzed coral and molluscan fossil assemblages from reefs near Bocas del Toro, Panama to construct a timeline of ecological change from the 19th century to the present.” This work revealed “large changes before 1960 in coastal lagoons coincident with extensive deforestation, and after 1960 on offshore reefs.” Some of the “striking changes” they identified include “the demise of previously dominant staghorn coral Acropora cervicornis and oyster Dendrostrea frons that lives attached to gorgonians and staghorn corals.” And they say that “reductions in bivalve size and simplification of gastropod trophic structure further implicate increasing environmental stress on reefs.” (more…)