Chaotic and non-chaotic population dynamics cannot be reliably differentiated by visual inspection of time series. In this random sample of chaotic and non-chaotic time series of insects, mammals, and phytoplankton (top to bottom), the left panels are chaotic, the right panels are not chaotic. Credit: Rogers et al., Nature Ecol & Evol 2022
Chaos in natural populations appears to be much more common than previously recognized, according to a new analysis by scientists at UC Santa Cruz and NOAA Fisheries.
Organisms’ populations in natural ecosystems fluctuate widely, and a key question for environmentalists is whether these fluctuations are regular (vary around some theoretically “stable” equilibrium), random (completely unpredictable), or chaotic. Chaotic systems, such as weather, can be predictable in the short term but not in the long term, and are very sensitive to small differences in initial conditions.
“Knowing whether these fluctuations are regular, chaotic, or random has important implications for how well, and to what extent in the future, we can predict population size and how they will respond to management interventions,” said Tanya Rogers. NOAA ecologist and fishing ecologist. researcher at the Institute of Marine Sciences of the UCSC.
Rogers is the first author of the new study, published on June 27 in Nature Ecology and evolution. Its co-authors are Bethany Johnson, a UCSC graduate student in applied mathematics, and Stephan Munch, a NOAA fisheries ecologist and adjunct professor at the UCSC in the departments of Applied Mathematics and Ecology and Evolutionary Biology.
The researchers found evidence of chaotic dynamics in more than 30 percent of the populations they analyzed in an ecological database. Previous meta-analyzes assessing the prevalence of chaos in natural field populations had found that chaos was absent or rare. But this may have been due to limited amounts of data and the use of inadequate methods, rather than the inherent stability of ecosystems, the authors said.
“There’s a lot more data now and the length of a series of time you have makes a big difference in detecting chaotic dynamics,” Munch said. “We also showed that the methodological assumptions made in previous meta-analyzes were skewed against the detection of chaos.”
For the new study, the researchers used new and up-to-date chaos detection algorithms and subjected them to rigorous testing in simulated data sets. They then applied the three best methods to a set of 172 time series of population from the Global Population Dynamics Database.
His analysis revealed interesting associations between chaotic dynamics, shelf life, and body size. Chaos was most prevalent among plankton and insects, least prevalent among birds and mammals, and intermediate among fish.
“Many short-lived species tend to have chaotic population dynamics, and these are also species that tend to have rise and fall dynamics,” Rogers said.
The results suggest that there may be intrinsic limits to ecological foresight and caution when using equilibrium-based approaches for conservation and management, especially for short-lived species.
“From a fisheries management perspective, we want to predict fish stocks so we can set limits for fishing harvests,” Rogers explained. “If we do not recognize the existence of chaos, we could be losing short-term forecasting possibilities using appropriate methods for chaotic systems, while at the same time having overconfidence in our ability to make long-term predictions.”
A new computer approach to recognizing chaos More information: Tanya Rogers, Chaos is not uncommon in natural ecosystems, Nature Ecology and evolution (2022). DOI: 10.1038 / s41559-022-01787-y. www.nature.com/articles/s41559-022-01787-y Provided by the University of California – Santa Cruz
Citation: The study finds that chaos is more common in ecological systems than previously thought (2022, June 27) recovered on June 27, 2022 from
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