White-Sand Savannas Expand at the Core of the Amazon After Forest Wildfires
Open accessAbstract
Across the tropics, climate change is increasing the frequency and severity of wildfires, exposing tropical forests to the risk of shifting into an open vegetation state. A recent satellite analysis of the Amazon basin suggests this might happen first in floodplains where forests are particularly fragile. We studied floodplain landscapes of the middle Rio Negro, covering ~ 4100 km 2 at the Central Amazon region, where forest ecosystems are dominant. We used Landsat images to map 40 years of wildfire history and test the hypothesis that repeatedly burnt forests fail to regenerate and can be replaced by white-sand savanna ecosystems. In the field, using a chronosequence of ‘time after the first fire’, we assessed changes in tree species composition, herbaceous cover and topsoil properties. Here we show that when these forests are repeatedly disturbed by wildfires, their soil gradually loses clay and nutrients and becomes increasingly sandy. In synchrony, native herbaceous cover expands, forest tree species disappear and white-sand savanna tree species become dominant. This drastic ecosystem shift happened within 40 years, likely accelerated by topsoil erosion. When recurrent fires maintain floodplain forests in an open vegetation state, topsoil erosion intensifies, transforming clay-rich soils into white-sand soils that may favour savanna tree species. Our findings reveal that white-sand savannas may expand through seasonally flooded ecosystems at the core of the Amazon, facilitated by wildfires.
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Repeated fires can lead to grass invasion, increased flammability and suppressed canopy recovery, particularly at the forest-savanna transition.
“Repeated fires can lead to grass invasion, increased flammability and suppressed canopy recovery, particularly at the forest-savanna transition.”
From Amazon dieback beyond the 21st century under high-emission scenarios by Earth System models (2025) · cites this paper as [60]
The Introduction and Soil Shift sections (pages unavailable) say recurrent fires can keep burnt forests open, while the Vegetation Shift section reports persistent herbaceous cover after fire. But the paper reports native herbs rather than grass invasion in its study sites, explicitly notes that non-native invasive grasses were absent, and studies floodplain forests at the Amazon’s core rather than establishing the claim particularly for forest–savanna transitions. (LLM, conf=0.86)
Experimental — accuracy not yet measuredAfter fire, the topsoil of burnt forests changes from clayey to sandy, favouring the establishment of savanna trees and native herbaceous plants.
“After fire, the topsoil of burnt forests changes from clayey to sandy, favouring the establishment of savanna trees and native herbaceous plants95.”
From Critical transitions in the Amazon forest system (2024) · cites this paper as [95]
The Soil Shift section says burnt floodplain forest soil shifts from clayey to sandy, while the Vegetation Shift section reports the arrival of savanna trees and the dominance of native herbaceous plants in burnt sites. But the paper says it cannot infer how soils and plants interact during this shift; it does not establish that the sandier soil favours the establishment of both plant groups. (LLM, conf=0.86)
Experimental — accuracy not yet measuredIn a remote landscape far from large agricultural frontiers, within a stable forest region of the Amazon, satellite and field evidence revealed that white-sand savannas are expanding where floodplain forests were repeatedly disturbed by fires.
“In a remote landscape far from large agricultural frontiers, within a stable forest region of the Amazon (Extended Data Fig. 1b), satellite and field evidence revealed that white-sand savannas are expanding where floodplain forests were repeatedly disturbed by fires95.”
From Critical transitions in the Amazon forest system (2024) · cites this paper as [95]
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Experimental — accuracy not yet measuredFire-vegetation feedbacks can reduce ecosystem resilience and promote persistent forest degradation.
“Recent studies highlight that fire-vegetation feedbacks can reduce ecosystem resilience and promote persistent forest degradation 26,59,60 .”
From Amazon dieback beyond the 21st century under high-emission scenarios by Earth System models (2025) · cites this paper as [60]
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Critical transitions in the Amazon forest system
Flores, B. M., Montoya, E., Sakschewski, B., Nascimento, N., Staal, A., Betts, R. A., Levis, C., Lapola, D. M., Esquível-Muelbert, A., Jakovac, C., et al. (2024) · Nature · doi:10.1038/s41586-023-06970-0 · Cited by 607 · see citing works
Self-citationAmazon dieback beyond the 21st century under high-emission scenarios by Earth System models
Melnikova, I., Hajima, T., Shiogama, H., Hayashi, M., Ito, A., Nishina, K., Tachiiri, K., & Yokohata, T. (2025) · Communications Earth & Environment · doi:10.1038/s43247-025-02606-5 · Cited by 5 · see citing works
- Authors
- Flores, B. M., & Holmgren, M.
- Affiliations
- Universidade Federal do Rio Grande do Norte (BR)
- Wageningen University & Research (NL)
- Corresponding author
- Flores, Bernardo M.
- Holmgren, Milena
- Venue
- Ecosystems
- Published
- 2021-03-03
- Volume
- 24
- Issue
- 7
- Pages
- 1624-1637
- ISSN
- 1432-9840 (ISSN-L)
- 1435-0629
- OpenAlex
- W3134872589
- Cited by
- 73
- References
- 3
- Citations by year
- 2026: 8 · 2025: 13 · 2024: 17 · 2023: 13 · 2022: 13 · 2021: 9
- FWCI
- 5.14
- Type
- journal article
- Language
- en
- Open access
- hybrid
- doi.org
- Locations
- Ecosystems (publishedVersion, cc-by)
- Socio-Environmental Systems Modeling (submittedVersion, cc-by)
- Data Archiving and Networked Services (DANS) (submittedVersion, cc-by)
- Funders
- Wageningen University and Research Centre
- Fundação de Amparo à Pesquisa do Estado de São Paulo (2016/25086-3)
- Fundação de Amparo à Pesquisa do Estado do Amazonas
- Conselho Nacional de Desenvolvimento Científico e Tecnológico
- Topics
- Physical Sciences › Environmental Science › Global and Planetary Change › Fire effects on ecosystems
- Physical Sciences › Environmental Science › Global and Planetary Change › Ecosystem dynamics and resilience
- Physical Sciences › Environmental Science › Nature and Landscape Conservation › Ecology and Vegetation Dynamics Studies
- Keywords
- forest fires, savanna expansion, floodplain forests, Amazon, Rio Negro, topsoil erosion, soil nutrient loss, forest-savanna transition, tree species composition, herbaceous cover, climate change, chronosequence, Central Amazon
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