It has long been assumed that "tipping points," qualitative changes in an ecosystem that often result in reduced ecosystem health are fixed values.
But a new study has shown that these tipping points are not fixed in human-impacted ecological systems and depend, instead, on human responses to a changing environment.
The study team involved University of Notre Dame ecologist David Lodge, Michigan State University economist Richard Horan, Arizona State University economist Eli Fenichel and Bethel College biologist Kevin Drury.
For the study, the researchers studied invasive rusty crayfish, which have transformed many Michigan and Wisconsin lakes from luxuriant underwater forests inhabited by many smaller animals that supported sport fish to clear-cut forests with diminished production of sport fish.
This outcome occurred despite the fact that there are many fish like smallmouth bass that readily consume crayfish.
"Our work explored whether a shift from one lake condition with excellent habitat to another lake condition with barren lake bottom is the inevitable result of invasion by crayfish or whether it is just one possible outcome," said Lodge.
"In other words, we asked whether we humans need to passively accept undesirable outcomes or whether, instead, the institutions and rules by which we make decisions can change the landscape of possibilities," he said.
The institutional rules shape the relationship among managers, users, and ecological systems. If the system is mapped using only ecological characteristics, then managers may not account for human responses to change, such as changing decisions about whether or how much to fish as fishing quality changes.
Their results showed that tipping points in human-impacted ecosystems are affected by regulatory choices that influence human behaviour.
"This gives us reason for optimism: if we give regulators sufficient flexibility it may be possible and cost-effective to manage ecological systems so that only desirable ecological outcomes arise and tipping points are eliminated," said Horan.
In particular, the researchers stress that their results highlight the importance of giving strong institutional support to regulatory agencies that aim to enhance societal wellbeing.
The study appeared in the Proceedings of the National Academy of Sciences (PNAS).