Regularity underlies erratic population abundances in marine ecosystems

Area of Science:

• Ecology
• Population Dynamics
• Conservation Biology

Background:

• Species population abundance is highly variable over time.
• Previous models of population variability do not fully account for key ecological factors.

Purpose of the Study:

• To develop a stochastic model for population dynamics using historical marine species data.
• To identify critical factors influencing population variability and extinction risk.
• To differentiate the impact of demographic stochasticity on species growth rates.

Main Methods:

• Analysis of historical marine species data.
• Development of a stochastic population model based on a double-exponential (Laplace) distribution.
• Separation of demographic stochasticity from common environmental stochasticity.

Main Results:

• Year-to-year population growth rate fluctuations follow a double-exponential distribution.
• Reduced growth at low population density is a critical, often overlooked, factor in population variability.
• Common stochasticity, not just demographic stochasticity, predominantly drives single-species growth rates.

Conclusions:

• Current extinction risk assessments may underestimate risks due to missed factors like density-dependent effects.
• Ecosystem-level management is essential for mitigating extinction risks for individual species.
• Understanding interspecies correlations and common stochasticity is vital for conservation.