Vegetation patterning can both impede and trigger critical transitions from savanna to grassland

Tree-grass coexistence is a defining feature of savanna ecosystems, which play an important role in supporting biodiversity and human populations worldwide. While recent advances have clarified many of the underlying processes, how these mechanisms interact to shape ecosystem dynamics under environm...

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Main Authors: Jelle van der Voort, Mara Baudena, Ehud Meron, Max Rietkerk, Arjen Doelman
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:Environmental Research Letters
Subjects:
Online Access:https://doi.org/10.1088/1748-9326/adc3ab
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author Jelle van der Voort
Mara Baudena
Ehud Meron
Max Rietkerk
Arjen Doelman
author_facet Jelle van der Voort
Mara Baudena
Ehud Meron
Max Rietkerk
Arjen Doelman
author_sort Jelle van der Voort
collection DOAJ
description Tree-grass coexistence is a defining feature of savanna ecosystems, which play an important role in supporting biodiversity and human populations worldwide. While recent advances have clarified many of the underlying processes, how these mechanisms interact to shape ecosystem dynamics under environmental stress is not yet understood. Here, we present and analyse a minimalistic spatially extended model of tree-grass dynamics in dry savannas. We incorporate tree facilitation of grasses through shading and grass competing with trees for water, both varying with tree life stage. Our model shows that these mechanisms lead to grass-tree coexistence and bistability between savanna and grassland states. Moreover, the model predicts vegetation patterns consisting of trees and grasses, particularly under harsh environmental conditions, which can persist in situations where a non-spatial version of the model predicts ecosystem collapse from savanna to grassland instead (a phenomenon called ‘Turing-evades-tipping’). Additionally, we identify a novel ‘Turing-triggers-tipping’ mechanism, where unstable pattern formation drives tipping events that are overlooked when spatial dynamics are not included. These transient patterns act as early warning signals for ecosystem transitions, offering a critical window for intervention. Further theoretical and empirical research is needed to determine when spatial patterns prevent tipping or drive collapse.
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spelling doaj-art-2b64a0037fb24c30a7eb1869e384134a2025-08-22T15:34:47ZengIOP PublishingEnvironmental Research Letters1748-93262025-01-0120909405210.1088/1748-9326/adc3abVegetation patterning can both impede and trigger critical transitions from savanna to grasslandJelle van der Voort0https://orcid.org/0000-0002-7710-3222Mara Baudena1https://orcid.org/0000-0002-6873-6466Ehud Meron2https://orcid.org/0000-0002-3602-7411Max Rietkerk3https://orcid.org/0000-0002-2698-3848Arjen Doelman4https://orcid.org/0000-0003-4369-4172Mathematical Institute, Leiden University , 2300 RA Leiden, The NetherlandsNational Research Council, Institute of Atmospheric Sciences and Climate (CNR-ISAC) , 10133 Torino, Italy; National Biodiversity Future Center (NBFC) , 90133 Palermo, ItalyThe Swiss Institute for Dryland Environmental and Energy Research, BIDR, Ben-Gurion University of the Negev , Midreshet Ben-Gurion 8499000, Israel; Physics Department, Ben-Gurion University of the Negev , Beer-Sheva 8410501, IsraelCopernicus Institute of Sustainable Development, Section Environmental Sciences, Utrecht University , Utrecht, The NetherlandsMathematical Institute, Leiden University , 2300 RA Leiden, The NetherlandsTree-grass coexistence is a defining feature of savanna ecosystems, which play an important role in supporting biodiversity and human populations worldwide. While recent advances have clarified many of the underlying processes, how these mechanisms interact to shape ecosystem dynamics under environmental stress is not yet understood. Here, we present and analyse a minimalistic spatially extended model of tree-grass dynamics in dry savannas. We incorporate tree facilitation of grasses through shading and grass competing with trees for water, both varying with tree life stage. Our model shows that these mechanisms lead to grass-tree coexistence and bistability between savanna and grassland states. Moreover, the model predicts vegetation patterns consisting of trees and grasses, particularly under harsh environmental conditions, which can persist in situations where a non-spatial version of the model predicts ecosystem collapse from savanna to grassland instead (a phenomenon called ‘Turing-evades-tipping’). Additionally, we identify a novel ‘Turing-triggers-tipping’ mechanism, where unstable pattern formation drives tipping events that are overlooked when spatial dynamics are not included. These transient patterns act as early warning signals for ecosystem transitions, offering a critical window for intervention. Further theoretical and empirical research is needed to determine when spatial patterns prevent tipping or drive collapse.https://doi.org/10.1088/1748-9326/adc3absavanna ecosystemsspatial dynamicsvegetation pattern formationecosystem resiliencecritical transitionsearly warning signals
spellingShingle Jelle van der Voort
Mara Baudena
Ehud Meron
Max Rietkerk
Arjen Doelman
Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
Environmental Research Letters
savanna ecosystems
spatial dynamics
vegetation pattern formation
ecosystem resilience
critical transitions
early warning signals
title Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
title_full Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
title_fullStr Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
title_full_unstemmed Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
title_short Vegetation patterning can both impede and trigger critical transitions from savanna to grassland
title_sort vegetation patterning can both impede and trigger critical transitions from savanna to grassland
topic savanna ecosystems
spatial dynamics
vegetation pattern formation
ecosystem resilience
critical transitions
early warning signals
url https://doi.org/10.1088/1748-9326/adc3ab
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