Populations, whether fish or people, can be even less predictable than the weather, according to an accurate new model created by researchers from the University of California, Davis, and University of Helsinki, Finland.
Population sizes can dive and soar dramatically, sometimes without apparent cause. Trying to figure out what drives the big swings is a question that has taunted researchers for years. In fact, one of the most important and fiercest debates in population biology swirls around whether populations go through boom and bust cycles primarily because of internal ways of regulating their numbers by changing things such as natural life expectancy, egg-laying rates and cannibalism, or because of outside forces, such as predators, weather and food.
It turns out that both sides may be right. A new paper being published in the May 30 issue of Science magazine fingers random external influences that are amplified by nonlinear internal dynamics as guilty parties in the wild swings.
Focusing on Dungeness crabs on the U.S. West Coast, the paper is authored by newly minted UC Davis doctoral recipient Kevin Higgins, UC Davis environmental studies chair Alan Hastings, University of Texas computer science graduate student Jacob Sarvela, and UC Davis wildlife, fish and conservation biology professor Louis Botsford.
The model stands out for several reasons. In particular, the model provides an extraordinary match with 42 years of data gathered from eight fishing regions along the West Coast.
The art of ecological modeling is in figuring out how to simplify complex systems to the few most important components while minimizing distortions. Modelers translate the relationships between those key components into equations and plug them into a computer. A model "works" when the equations spit out answers that resemble the actual data. Then, the modelers believe they have pinpointed some essential dynamics that could help explain how a com