In many habitats and in many places, human-caused environmental impacts preceded scientific surveys of the now-affected species and their environments. How can you measure environmental change without a baseline? How can you restore habitats when you don’t know the reference conditions? Under the right circumstances, accumulated skeletal remains provide a record of pre-impact species and their habitats.
We used the hard-part remains of bivalve molluscs, scianid fish and marine mammals to reconstruct the, “pre-dambrian” abundance, trophic interactions, growth rates, salinity tolerances and relative mortality rates of ecologically important species of the Colorado River estuary. Radiocarbon and amino-acid dating provide a chronology, oxygen isotopes can be a proxy for salinity, predatory damage on shells records trophic relationships and differences in the relative abundance of living and dead species demonstrate changes in mortality rates. A now-rare bivalve mollusk once dominated the brackish water of the estuary. It was prey to drilling gastropods and edge-peeling crabs. The geographic distribution of its empty shells documents the >60 km reach of the river’s freshwater plume. A now-endangered fish once grew faster in the brackish nursery grounds of the estuary. The over-representation of beached skulls of a rare marine mammal document its high mortality as bycatch.
Armed with the simple tools of faunal surveys, geochronology, geochemistry, and forensic science, conservation paleobiologists can convince the dead to give up their secrets in order to serve the living.