Karl Flessa

Photo of Karl Flessa


Karl Flessa

Professor of Geosciences





My active research concerns how we can use the very recent fossil record to address important issues in conservation biology and environmental change. Karl Flessa sitting on a dinosaur playground piece

My students and I examine how skeletal remains accumulate, how assemblages of dead remains differ from contemporaneous living communities, and how variation in stable isotopes, growth rings and predatory damage can be used to reconstruct environments and past ecological interactions. In short, we are putting the dead to work to assess environmental impact and to provide guidelines for habitat and species restoration.

In addition to this field- and lab-based work on young fossils, I am examining the environmental and ecological impact of water policy in the western United States. And I’m an avid collector of roadside dinosaurs.

Most of my lab’s work focuses on the delta of the Colorado River. Since about 1935, upstream water diversions have reduced the amount of water that reaches the river’s delta in the northern Gulf of California. In most years, the river no longer reaches the sea. We are examining deposits of mollusk shells, bones of marine mammals, and otoliths of fish in order to assess the impact of upstream water diversions on the delta and estuary of the Colorado River. We also use oxygen isotopes in dated clamshells to compare the variation in river flow during the past 1,000 years to the variation evident in the 100 years of the instrumental record.

I currently serve as the Chief Scientist for the Minute 323 Monitoring and Science Team for the Colorado River Delta.  The team is responsible for evaluating the environmental and hydrologic effects of the environmental flows delivered to the delta under the terms of the U.S.-Mexico Water Treaty.  For a look at delta restoration, see https://tv.azpm.org/p/originals-azill-sci/2019/4/29/150657-the-delta/.

Recent CV

Office: Gould-Simpson Bldg. 319
Phone: 520-621-7336
Fax: 520-621-2672