Many changes in nature are slow and gradual, but sometimes extensive changes happen fast. Droughts, losses of production from rangelands, collapse of fisheries, toxic algae blooms, and outbreaks of disease or invasive species can occur rapidly, with significant impacts on living resources and large costs to society. Such big changes are difficult to forecast. Recent theoretical advances suggest that certain indicators can help foresee and manage big changes in resources before they occur. Like leading economic indicators, these leading ecological indicators can be observed before a big shift. So far these theories have not been tested in the field. This project will test potential indicators by experimentally inducing massive changes in the food chain of a lake, while monitoring the lake before, during and after the changes using modern sensor and signal processing technology. The research will evaluate the sensitivity of the indicators and whether they can be used to detect a large change in advance.
The project will assess leading indicators that could potentially be used to manage a wide range of living resources, while at the same time testing new theory about rapid extensive changes in nature. We will present a workshop and field trip on rapid environmental change for journalists at the Society of Environmental Journalists meeting in Madison in fall 2009. The project will train graduate and undergraduate students and contribute teaching materials for courses at the Institute of Ecosystem Studies, St. Norbert College, and University of Wisconsin-Madison.
By closely monitoring the conditions of a remote lake, we found that environmental collapse shares characteristics of the early warnings of collapse in human health and the economy. St. Norbert College scientist Jim Hodgson was part of the research team, whose findings were recently published in the journal Science. The paper was the first to show that by paying attention to variability in key ecosystem processes, scientists can detect the warning signs of environmental collapse. Forecasting regime shifts — the reorganization of an ecosystem from one state to another — is critical to identifying ecosystems that will fail without intervention. In a large field experiment, the team triggered a regime shift in a freshwater lake by introducing a predatory fish. The study lake was originally dominated by small fish that feed on tiny free-swimming invertebrates. We destabilized the lake by adding largemouth bass. The goal: to observe the cascade of environmental changes that eventually led to a food web dominated by piscivorous, or fish-eating, fish. As the number of bass increased, smaller fish spent more time swimming in groups near the shoreline, to avoid being eaten. Freed from predation, invertebrates living in the open water, such as water fleas, shifted to forms that were larger in size. Phytoplankton, the tiny plants that are a dietary staple of these invertebrates, became more variable. Within three years the lake's food web was dominated by large fish-eating fish and larger free-swimming invertebrates. By analyzing massive sets of data, we were able to detect early warning signals that an ecosystem shift was looming. More than a year before the food web transition was complete, variance in chlorophyll — the green pigment found in plants and algae — was an indicator of the impending food web regime shift. The study represents the first time that an early warning system for ecosystem collapse has been validated in the field. If similar signals could be identified in other types of ecosystems, they could help prevent a range of environmental meltdowns. The catch? For the early warning systems to work, scientists need to know an ecosystem's chemical, physical and biological properties. The chlorophyll red flag would only work for identifying food web shifts in freshwater lakes. The Science paper highlights the importance of long-term environmental monitoring efforts. Without them, environmental regime change predictions are impossible. In the future, the marriage between long-term monitoring efforts and predictive statistics will be a valuable tool in managing resources in a changing world. Broader Impacts The project provided research experiences for undergraduates and graduate students at the Universities of Virginia and Wisconsin and St. Norbert College. Data and other findings from this project were used in university courses, including graduate seminars taught by Carpenter, course in Ecosystem Ecology and Inland Water Systems taught by Pace, Fundamentals of Ecosystem Ecology co-taught by Cole and limnology by Hodgson. Our 2011 paper in Science triggered more than 20 media interviews and scores of media reports. A sampling of the media reports is collected on http://limnology.wisc.edu/CFL_in_the_News.php#Environment
