Thesis: Fluctuations in Populations Forecast Catastrophic Changes in Ecosystem

Today, on September 25^th, Neeme Lumi from the Tallinn University School of Natural Sciences and Health will defend his doctoral thesis, in which he proposes four models of population dynamics in the presence of  coloured noise, which help us understand how different populations react in the environment of intermittent stochastic parameters.

The growth dynamics of both biological and non-biological populations are affected by various changes in the environment. Neeme Lumi researched two types of non-linear models to describe the influence of such changes and systematic periodical deterministic disturbances to the dynamics of populations.

Neeme Lumi emphasises two important findings in his research: “The analysis of the symbiotic meta-population growth model showed that the more intensive the symbiosis between subpopulations, the more sensitive the meta-population is to the influence of random changes in the environment. From this we can deduce that the volumes of natural populations can strongly oscillate or rapidly change between stable states due to faint periodic external disturbances and intermittent changes in the environmental parameters.”

An even more important result is the pattern, in which the increased oscillation of population volumes can be a cautionary indicator to an upcoming catastrophic regime change in the ecosystem. This means that the large oscillations in population volumes indicate a possible future rapid growth or plunge in the population, or even its extinction.

Unlike earlier research in this field, this doctoral thesis takes into consideration two parameters, the concurrence of a faint periodic external disturbance and intermittent changes, which enables a more accurate description in population growth trends.

Lumi argues the results of this thesis can be used in real research on populations of the growth dynamics of symbiotic meta-populations: “The factors of a technogenic environment influence the growth dynamics of a population. Being aware of such influence enables us to conceive methods to help keep these factors at bay and maintain the stability within a certain ecological biome.”

Neeme Lumi’s doctoral thesis “Colored-Noise-Induced Transitions in Non-Linear Population Growth Models / Värvilised müra indutseeritud üleminekud mittelineaarsetes populatsiooni kasvumudelites” was supervised by Professor Romi Mankin and associate professor Astrid Rekker, both of Tallinn University. His opponents are professor Teet Örd from Tartu University and professor Michail D. Todoroy from Sofia University, Bulgaria.

The doctoral thesis can be accessed via the Tallinn University Academic Library ETERA.

The public defence of the doctoral thesis will take place today, on Friday, September 25^th at 14:00 at the Tallinn University auditorium M-213 (Uus-Sadama 5).