@St. Norbert June 2011 - Biologist’s work appears in Science St. Norbert College
@St. Norbert
Jim Hodgson

Jim Hodgson (Biology) retires this summer after 41 years at St. Norbert College.

June 2011

Lake effect: Biologist’s work appears in Science


The journal Science is taking note of work by Jim Hodgson (Biology). He and his colleagues find they can predict radical changes to an Upper Michigan ecosystem before they occur – possibly even in time to prevent serious damage.

The team was researching regime shifts – the sudden, unexpected and often catastrophic reorganization of ecosystems from one stable state to another. On a larger scale, such shifts could include the desertification of rangeland, collapse of commercial fisheries, or an ecosystem’s response to climate change, shifts that often damage ecosystems irreversibly.

“The findings are a benchmark in science,” says Hodgson. “They have extreme relevance to ecosystem management and general public interest relative to ecosystem services.”

A complex study
Hodgson worked with colleagues from the University of Wisconsin-Madison, the University of Virginia and other institutions renowned for their research initiatives to produce and publish the report, which appeared in the journal this April.

The scientists theorized that they could predict such alterations to ecosystems and better avoid regime shifts by noting statistical “early warning signals.”

They tested their hypothesis in two adjacent lakes on Michigan’s Upper Peninsula by altering one lake’s trophic cascade, which highlights the interdependence of all levels of the food web. Hodgson and his fellow researchers introduced a top predator fish, the largemouth bass, to one lake in order to induce a regime shift in the food web. They left the second lake’s ecosystem unchanged.

Through careful monitoring of signals like chlorophyll concentration, algal growth, zooplankton biomass and forage fish schooling behavior, they were able to determine the ecosystem’s “tipping points” and identify the warning signals of regime shift more than a year prior to the actual shift.

The study took three years to complete and was extremely difficult to undertake, says Hodgson, due to the sensitivity and complexity of the ecosystem and the massive sets of data the team accrued, as some measurements had to be taken every five minutes. 

The team’s conclusion is unique because of its real-world nature and applicability. Hodgson stresses that the study lays a solid base for much more research on larger, more diverse ecosystems. The discovery of “tipping points” in a simpler ecosystem, like a small lake, may allow others to apply the idea to larger ecosystems, like those affected by climate change.

A collaborative effort
To undertake a study this complex, Hodgson collaborated with a research team that included colleagues he met through graduate courses and during a sabbatical at the University of Wisconsin-Madison. Their collective interest in the two lakes reaches back to the 1980s, when they collaborated on a different project that analyzed the changing food web in the lakes.

Several researchers from the Cary Institute of Ecosystems also joined the study, and numerous master’s and doctoral students rounded out the team of researchers. 

Hodgson stresses the importance of research collaborations between students of all educational levels and faculty members. Each member of the study brought specific and essential expertise to the research project, which was vital to the success of the study and the report.

June 7, 2011

  St. Norbert College • De Pere, Wisconsin http://www.snc.edu/communications/enews/0611/hodgson.html