What was done
The authors examined "the historical interactions between human populations and coral reef ecologies in Palau by combining known archaeological data and results from modern biological data of different reef fauna," hoping to thereby be able "to explain variations in taxa composition between islands in the archipelago and how this may relate to human exploitation or other phenomena through time."

What was learned
Fitzpatrick and Donaldson report that over the past few thousand years, "there has been increasing exploitation of coral reef resources, particularly finfish and mollusks, leading to a decline in taxa numbers, richness, and diversity in various locales," and that some of the studied sites of Palau "have signs of over-harvesting that are not necessarily linked with other factors such as environment or archaeological recovery methods."

What it means
These findings conform with the worldview of earth's corals that has been advanced by Pandolfi et al. (2003), who posit that "the long-term historic sequence of ecosystem decline is unknown for any reef, thereby obscuring the potential linkage and interdependence of the different responsible factors that must be unraveled for successful restoration and management." They also provide strong evidence for the validity of the hypothesis of Jackson et al. (2001), who suggest that "humans have been disturbing marine ecosystems since they first learned how to fish." Consequently, in order to correctly discern the reasons for the decreases in coral reef resiliency that have occurred over the past several decades, such as their increasing tendency to bleach in response to periods of high-temperature stress, it is necessary to know what has occurred to them over the past several centuries. And when this approach is taken, real-world observations of both the past and present suggest that earth's coral reefs are quite capable of maintaining themselves, and even flourishing, in the face of rising atmospheric CO2 concentrations and/or temperatures if humanity's many localized assaults upon them (such as increased physical destruction, heightened pollution, augmented sedimentation, and fishing) do not completely destroy them first. See also, in this regard, Coral Reefs (History).

References
Jackson, J.B.C., Kirby, M.X., Berger, W.H., Bjorndal, K.A., Botsford, L.W., Bourque, B.J., Bradbury, R.H., Cooke, R., Erlandson, J., Estes, J.A., Hughes, T.P., Kidwell, S., Lange, C.B., Lenihan, H.S., Pandolfi, J.M., Peterson, C.H., Steneck, R.S., Tegner, M.J. and Warner, R.R. 2001. Historical overfishing and the recent collapse of coastal ecosystems. Science 293: 629-638.

Pandolfi, J.M., Bradbury, R.H., Sala, E., Hughes, T.P., Bjorndal, K.A., Cooke, R.G., McArdle, D., McClenachan, L., Newman, M.J.H., Paredes, G., Warner, R.R. and Jackson, J.B.C. 2003. Global trajectories of the long-term decline of coral reef ecosystems. Science 301: 955-958.