HomeScience and ResearchSustainabilityChaos Was Never Rare In Natural Ecosystem, New Study Reveals

Chaos Was Never Rare In Natural Ecosystem, New Study Reveals

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It’s possible that methodological and data restrictions, rather than ecosystems’ fundamental stability, are to blame for the notion that chaos is uncommon in natural populations.

Researchers from UC Santa Cruz and NOAA Fisheries have conducted new research that suggests chaos in natural populations may occur far more frequently than previously thought.

Ecologists commonly debate whether population variations in natural ecosystems are regular (changing around a supposedly “stable” equilibrium), random (totally unpredictable), or chaotic. Like the weather, chaotic systems can be predicted in the short term but not in the long term, and they are extremely sensitive to minute variations in the starting circumstances.

Chaos Was Never Rare In Natural Ecosystem, New Study Reveals
Chaos Was Never Rare In Natural Ecosystem, New Study Reveals

Tanya Rogers, an NOAA Fisheries ecologist and research fellow at UCSC’s Institute of Marine Sciences, said that understanding whether these fluctuations are regular, chaotic, or random has significant implications for how well and how far into the future we can predict population sizes and how they will respond to management interventions.

Rogers is the first author of the new Nature Ecology & Evolution paper. Bethany Johnson, a doctoral student in applied mathematics at UCSC, and Stephan Munch, an adjunct professor in the departments of applied mathematics and ecology and evolutionary biology at UCSC, are her coauthors.

Over 30% of the populations in the ecological database showed signs of chaotic dynamics, according to the study. In previous meta-analyses, the frequency of chaos in natural field populations was shown to be negligible or low. However, the authors argued that this might not reflect the fundamental stability of ecosystems but rather the limitations of the data and the methodologies used.

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, right panels are not chaotic. Image credit: Rogers et al., Nature Ecol & Evol 2022

“There’s a lot more data now, and how long a time series you have makes a big difference for detecting chaotic dynamics,” said Munch. They also demonstrated “that methodological assumption made in prior meta-analyses were biased against detecting chaos”.

The researchers used fresh and improved chaos detection algorithms for the new study and rigorously tested them on simulated data sets. They then used a dataset of 172 population time series from the Global Population Dynamics Database to apply the three most effective techniques.

Their research showed that there were some interesting links between chaotic behavior, lifespan, and body size. Plankton and insects had the highest levels of chaos, whereas birds and mammals showed the lowest levels, and fish exhibited a middle level of chaos.

In addition to having chaotic population dynamics, short-lived species also frequently exhibit boom-and-bust dynamics, according to Rogers.

The findings warn against using equilibrium-based approaches to conservation and management, especially for short-lived species, and show that ecological forecasting may have inherent limitations.

According to Rogers, “from the fisheries management perspective, we want to predict fish populations so we can set limits for fishery harvests.”

If we don’t acknowledge the existence of chaos, “we could be losing out on short-term forecasting possibilities using methods appropriate for chaotic systems, while being overconfident about our ability to make long-term predictions.”

Image Credit: Getty

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