Finite-size effects, demographic noise, and ecosystem dynamics

Majumder, S and Das, A and Kushal, A and Sankaran, S and Guttal, V (2021) Finite-size effects, demographic noise, and ecosystem dynamics. In: European Physical Journal: Special Topics .

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Abstract

Strong positive feedback is considered a necessary condition to observe abrupt shifts in ecosystems. A few previous studies have shown that demographic noise�arising from the probabilistic and discrete nature of birth and death processes in finite systems�makes the transitions gradual. In this paper, we investigate the impact of demographic noise on finite ecological systems. We use a simple cellular automaton model with births and deaths influenced by positive feedback processes. We present our methods in a tutorial like format. Using the approach of van Kampen�s system-size expansion, we derive a stochastic differential equation that describes how local probabilistic rules scale to stochastic population dynamics in finite systems. We illustrate that as a consequence of enhanced demographic noise, finite-sized ecological systems can show an �effective abrupt transition� even with weak positive interactions. Numerical simulations of our spatially explicit model confirm this analytical expectation. Thus, we predict that small-sized populations and ecosystems, in response to environmental drivers, are prone to abrupt collapse while larger systems�with the same microscopic interactions�show a smooth response. © 2021, The Author(s), under exclusive licence to EDP Sciences, Springer-Verlag GmbH Germany, part of Springer Nature.

Item Type:	Journal Article
Publication:	European Physical Journal: Special Topics
Publisher:	Springer Science and Business Media Deutschland GmbH
Additional Information:	The copyright for this article belongs to Springer Science and Business Media Deutschland GmbH
Department/Centre:	Division of Biological Sciences > Centre for Ecological Sciences Division of Physical & Mathematical Sciences > Physics
Date Deposited:	30 Aug 2021 06:43
Last Modified:	30 Aug 2021 06:43
URI:	http://eprints.iisc.ac.in/id/eprint/69544

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