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Academic Minute

Dr. Aaron Ellison, Harvard Forest – Ecosystems and Tipping Points


In today’s Academic Minute, Dr. Aaron Ellison of Harvard University’s Harvard Forest describes efforts to intervene before ecosystems pass their tipping points. 

Aaron Ellison is the Senior Research Fellow in Ecology at Harvard University’s Harvard Forest, and an adjunct professor in the departments of Biology and Environmental Conservation at the University of Massachusetts at Amherst. He has authored or co-authored over 100 scientific papers and in 2012 he published A Field Guide to the Ants of New England. He earned his Ph.D. at Brown University.

About Dr. Ellison

Dr. Aaron Ellison – Ecosystems and Tipping Points

We are all familiar with “healthy” ecosystems and “sick” ones – a canonical example is the difference between clear blue lakes, and polluted green ones. Lakes and ponds shift from blue to green when excessive nutrients flow into them, causing aquatic plants to grow exuberantly but then die en masse, after which bacteria use up all the available oxygen decomposing the mats of dead plants. But where does this domino effect begin? How much nutrient loading is “excessive” and can we detect early warning signs soon enough to intervene?

Several years ago, my research group showed that the best available early-warning indicators of tipping points in lakes require nearly 50 years of advance warning to stop the shift. Neither science nor society has that kind of time. So, with support from the National Science Foundation we are using a miniature aquatic ecosystem – the microscopic collection of bacteria and flies that live within the small pools of water in New England’s purple pitcher plant – to develop better early-warning indicators of tipping points and environmental change.

In greenhouse experiments, we track the complete set of proteins – the proteome – expressed by all of the bacteria in the pitcher-plant microecosystem after organic matter is added to the water. Because bacteria reproduce rapidly, producing a new generation of microbes every hour, two days of changes in the bacterial proteome is similar to 50 years of changes in aquatic plants and fish. Now that we can predictably shift a micro-lake from blue to green in a matter of days, we can develop new proteome-based indicators to rapidly forecast and manage tipping points in a wide range of ponds, lakes, and streams.

Production support for the Academic Minute comes from Newman’s Own, giving all profits to charity and pursuing the common good for over 30 years, and from Mount Holyoke College.

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