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Synergistic impacts of anthropogenic fires and aridity on plant diversity in the Western Ghats: implications for management of ancient social-ecological systems

Synergistic impacts of anthropogenic fires and aridity on plant diversity in the Western Ghats: implications for management of ancient social-ecological systems
Synergistic impacts of anthropogenic fires and aridity on plant diversity in the Western Ghats: implications for management of ancient social-ecological systems
Identifying the impacts of anthropogenic fires on biodiversity is imperative for human-influenced tropical rainforests because: i) these ecosystems have been transformed by human-induced fires for millennia; and ii) their effective management is essential for protecting the world's terrestrial biodiversity in the face of global environmental change. While several short-term studies elucidate the impacts of fires on local plant diversity, how plant diversity responds to fire regimes over long timescales (>100 years) is a significant knowledge gap, posing substantial impediment to evidence-based management of tropical social-ecological systems. Using wet evergreen forests of the Western Ghats of India as a model system, we discuss the synergistic effects of anthropogenic fires and enhanced aridity on tropical plant diversity over the past 4000 years by examining fossil pollen-based diversity indices (e.g., pollen richness and evenness, and temporal β-diversity), past fire management, the intervals of enhanced aridity due to reduced monsoon rainfall and land use history. By developing a historical perspective, our aim is to provide region-specific management information for biodiversity conservation in the Western Ghats. We observe that the agroforestry landscape switches between periods of no fires (4000-1800 yr BP, and 1400-400 yr BP) and fires (1800-1400 yr BP, and 400-0 yr BP), with both fire periods concomitant with intervals of enhanced aridity. We find synergistic impacts of anthropogenic fires and aridity on plant diversity uneven across time, pointing towards varied land management strategies implemented by the contemporary societies. For example, during 1800–1400 yr BP, diversity reduced in conjunction with a significant decrease in the canopy cover related to sustained use of fires, possibly linked to large-scale intensification of agriculture. On the contrary, the substantially reduced fires during 400–0 yr BP may be associated with the emergence of sacred forest groves, a cultural practice supporting the maintenance of plant diversity. Overall, notwithstanding apparent changes in fires, aridity, and land use over the past 4000 years, present-day plant diversity in the Western Ghats agroforestry landscape falls within the range of historical variability. Importantly, we find a strong correlation between plant diversity and canopy cover, emphasising the crucial role of maintenance of trees in the landscape for biodiversity conservation. Systematic tree management in tropical social-ecological systems is vital for livelihoods of billions of people, who depend on forested landscapes. In this context, we argue that agroforestry landscapes can deliver win-win solutions for biodiversity as well as people in the Western Ghats and wet tropics at large.
Agroforestry, Biodiversity conservation, Evidence-based policymaking, Fire management, Social-ecological systems, Wet tropics
0301-4797
Kulkarni, Charuta
2a1332e7-f1b0-4c56-a3b9-32030b2e728c
Finsinger, Walter
3092724e-9888-4f8d-8b80-2ae6ecf179d1
Anand, Pallavi
25ea12f3-4a91-4587-83a0-568f6d0ece4f
Nogué, Sandra
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Bhagwat, Shonil A.
394d7c39-9728-42f4-9bab-a1a336025860
Kulkarni, Charuta
2a1332e7-f1b0-4c56-a3b9-32030b2e728c
Finsinger, Walter
3092724e-9888-4f8d-8b80-2ae6ecf179d1
Anand, Pallavi
25ea12f3-4a91-4587-83a0-568f6d0ece4f
Nogué, Sandra
5b464cff-a158-481f-8b7f-647c93d7a034
Bhagwat, Shonil A.
394d7c39-9728-42f4-9bab-a1a336025860

Kulkarni, Charuta, Finsinger, Walter, Anand, Pallavi, Nogué, Sandra and Bhagwat, Shonil A. (2021) Synergistic impacts of anthropogenic fires and aridity on plant diversity in the Western Ghats: implications for management of ancient social-ecological systems. Journal of Environmental Management, 283, [111957]. (doi:10.1016/j.jenvman.2021.111957).

Record type: Article

Abstract

Identifying the impacts of anthropogenic fires on biodiversity is imperative for human-influenced tropical rainforests because: i) these ecosystems have been transformed by human-induced fires for millennia; and ii) their effective management is essential for protecting the world's terrestrial biodiversity in the face of global environmental change. While several short-term studies elucidate the impacts of fires on local plant diversity, how plant diversity responds to fire regimes over long timescales (>100 years) is a significant knowledge gap, posing substantial impediment to evidence-based management of tropical social-ecological systems. Using wet evergreen forests of the Western Ghats of India as a model system, we discuss the synergistic effects of anthropogenic fires and enhanced aridity on tropical plant diversity over the past 4000 years by examining fossil pollen-based diversity indices (e.g., pollen richness and evenness, and temporal β-diversity), past fire management, the intervals of enhanced aridity due to reduced monsoon rainfall and land use history. By developing a historical perspective, our aim is to provide region-specific management information for biodiversity conservation in the Western Ghats. We observe that the agroforestry landscape switches between periods of no fires (4000-1800 yr BP, and 1400-400 yr BP) and fires (1800-1400 yr BP, and 400-0 yr BP), with both fire periods concomitant with intervals of enhanced aridity. We find synergistic impacts of anthropogenic fires and aridity on plant diversity uneven across time, pointing towards varied land management strategies implemented by the contemporary societies. For example, during 1800–1400 yr BP, diversity reduced in conjunction with a significant decrease in the canopy cover related to sustained use of fires, possibly linked to large-scale intensification of agriculture. On the contrary, the substantially reduced fires during 400–0 yr BP may be associated with the emergence of sacred forest groves, a cultural practice supporting the maintenance of plant diversity. Overall, notwithstanding apparent changes in fires, aridity, and land use over the past 4000 years, present-day plant diversity in the Western Ghats agroforestry landscape falls within the range of historical variability. Importantly, we find a strong correlation between plant diversity and canopy cover, emphasising the crucial role of maintenance of trees in the landscape for biodiversity conservation. Systematic tree management in tropical social-ecological systems is vital for livelihoods of billions of people, who depend on forested landscapes. In this context, we argue that agroforestry landscapes can deliver win-win solutions for biodiversity as well as people in the Western Ghats and wet tropics at large.

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Accepted/In Press date: 4 January 2021
e-pub ahead of print date: 22 January 2021
Published date: 1 April 2021
Additional Information: Funding Information: Our work is part of ‘EARNEST: Examining the Agroforestry Landscape Resilience in India to inform Social-Ecological Sustainability in the Tropics’, a project funded by the European Union Horizon 2020 research and innovation programme through a Marie Skłodowska-Curie Actions Individual Fellowship awarded to Charuta Kulkarni, under the grant agreement no. 795557 . We thank T. Brncic for help with coring, C.G. Kushalappa, and the College of Forestry for field assistance. We are grateful to R. Premathilake, K. Anupama, S. Prasad, and the Palynology Laboratory at the French Institute, Pondicherry, for their help with pollen identification. We thank D. Sinclair, Oxford Long Term Ecology Laboratory for her help in sub-sampling of the core, and S. Subitani and I. Figueiral from ISEM, Montpellier for their help in macroscopic charcoal processing and identification. Special thanks to P. Rodríguez-Zorro, R. Cassino, S. Yoshi Maezumi for interesting outlooks on ecology and fire regimes in other parts of the tropics. We extend our deep gratitude towards K. J. Willis, C. G. Kushalappa, and R. Premathilake regarding their insightful comments on the early stages of this work. Publisher Copyright: © 2021 Elsevier Ltd Copyright: Copyright 2021 Elsevier B.V., All rights reserved.
Keywords: Agroforestry, Biodiversity conservation, Evidence-based policymaking, Fire management, Social-ecological systems, Wet tropics

Identifiers

Local EPrints ID: 447436
URI: http://eprints.soton.ac.uk/id/eprint/447436
ISSN: 0301-4797
PURE UUID: e90893ca-d4ef-49eb-92ad-9f9129bbcb7a
ORCID for Sandra Nogué: ORCID iD orcid.org/0000-0003-0093-4252

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Date deposited: 11 Mar 2021 17:35
Last modified: 22 Nov 2021 03:09

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Contributors

Author: Charuta Kulkarni
Author: Walter Finsinger
Author: Pallavi Anand
Author: Sandra Nogué ORCID iD
Author: Shonil A. Bhagwat

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