Fire weather severity in southern Africa is increasing faster and more extensively in the late than in the early dry season

Sílvia Catarino; João M. N. Silva; Alana K. Neves; Duarte Oom; José M. C. Pereira

doi:10.1071/WF24002

RESEARCH ARTICLE (Open Access)

Previous Next Contents Vol 34(3)

Fire weather severity in southern Africa is increasing faster and more extensively in the late than in the early dry season

Sílvia Catarino

^A ^C ^* , João M. N. Silva ^A , Alana K. Neves ^A ^D , Duarte Oom ^B and José M. C. Pereira

^A

+ Author Affiliations

- Author Affiliations

^A Forest Research Centre (CEF), Associate Laboratory TERRA, School of Agriculture, University of Lisbon, Tapada da Ajuda, 1349-017, Lisbon, Portugal.

^B European Commission, Joint Research Centre, Ispra Site, Ispra, Italy.

^C Present address: Centre for Ecology, Evolution and Environmental Changes (cE3c) & CHANGE – Global Change and Sustainability Institute, Faculty of Sciences, University of Lisbon, 1749-016, Lisbon, Portugal.

^D Present address: GRAS Global Risk Assessment Services GmbH, 50672, Köln, Deutschland.

^* Correspondence to: scatarino@isa.ulisboa.pt

International Journal of Wildland Fire 34, WF24002 https://doi.org/10.1071/WF24002

Submitted: 9 January 2024 Accepted: 14 February 2025 Published: 13 March 2025

© 2025 The Author(s) (or their employer(s)). Published by CSIRO Publishing on behalf of IAWF. This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND)

Abstract

Background

In African savannas, the most intense fires occur during the late dry season, when fuel availability is high and atmospheric relative humidity low. The Fire Weather Index (FWI) system has been used to measure the effort required for fire suppression and explore the impact of climate on fires.

Aims

This study assesses trends in FWI system indices from 1979 to 2022 and their influence on burned area (BA).

Methods

We employed the Theil–Sen slope estimator and contextual Mann–Kendall test to evaluate the presence of significant trends in FWI system indices during the early dry season (EDS) and late dry season (LDS), and assessed how trends in BA depend on fire weather.

Key results

We found distinct patterns in fire weather trends between the EDS and LDS, the LDS showing more widespread areas of increasing trends. However, only 28% of the regression analyses showed significant relationships with BA, suggesting a moderate influence of the FWI system on BA interannual variance.

Conclusions

Fire weather severity is increasing faster and more extensively during the LDS than the EDS. Additional factors play a significant role in shaping BA trends. Proactively managing anthropogenic fires during the moister EDS can help mitigate fire intensity, reduce emissions and support biodiversity conservation efforts.

Keywords: burned area, contextual Mann–Kendall, fine fuel moisture content, fire danger, Fire Weather Index, FWI, Initial Spread Index, ISI, late dry season, LDS, southern Africa, spatiotemporal trends, time series.

References

Archibald S (2016) Managing the human component of fire regimes: lessons from Africa. Philosophical Transactions of the Royal Society B: Biological Sciences 371, 20150346.
| Crossref | Google Scholar |

Archibald S, Scholes RJ, Roy DP, Roberts G, Boschetti L (2010a) Southern African fire regimes as revealed by remote sensing. International Journal of Wildland Fire 19, 861-878.
| Crossref | Google Scholar |

Archibald S, Nickless A, Govender N, Scholes RJ, Lehsten V (2010b) Climate and the inter‐annual variability of fire in southern Africa: a meta‐analysis using long‐term field data and satellite‐derived burnt area data. Global Ecology and Biogeography 19, 794-809.
| Crossref | Google Scholar |

Archibald S, Beckett H, Bond WJ, Coetsee C, Druce DJ, Staver CA (2017) Interactions between fire and ecosystem processes. In ‘Conserving Africa’s Megadiversity in the Anthropocene: The Hluhluwe–iMfolozi Park story’. (Eds JP Cromsigt, S Archibald, N Owen-Smith) pp. 233–262. (Cambridge University Press: Cambridge)

Artés T, Oom D, De Rigo D, Durrant TH, Maianti P, Libertà G, San-Miguel-Ayanz J (2019) A global wildfire dataset for the analysis of fire regimes and fire behaviour. Scientific Data 6, 296.
| Crossref | Google Scholar |

Barbosa PM, Stroppiana D, Grégoire JM, Pereira JMC (1999) An assessment of vegetation fire in Africa (1981–1991): burned areas, burned biomass, and atmospheric emissions. Global Biogeochemical Cycles 13, 933-950.
| Crossref | Google Scholar |

Barry MB, Badiane D, Sall SM, Diakhaté M, Senghor H (2019) Fire activity and their relationship with the global fire weather index database components in Guinea. Environmental Management and Sustainable Development 8, 18-41.
| Crossref | Google Scholar |

Bedia J, Herrera S, Gutiérrez JM, Benali A, Brands S, Mota B, Moreno JM (2015) Global patterns in the sensitivity of burned area to fire-weather: implications for climate change. Agricultural and Forest Meteorology 214, 369-379.
| Crossref | Google Scholar |

Bond WJ (Ed.) (2019) ‘Open ecosystems: ecology and evolution beyond the forest edge’. (Oxford University Press: Oxford, UK)

Boschetti L, Roy DP, Giglio L, Huang H, Zubkova M, Humber ML (2019) Global validation of the Collection 6 MODIS burned area product. Remote Sensing of Environment 235, 111490.
| Crossref | Google Scholar |

Campbell BM (Ed.) (1996) ‘The Miombo in transition: woodlands and welfare in Africa’. (Center for International Forestry Research: Malaysia)

Catarino S, Romeiras MM, Figueira R, Aubard V, Silva JM, Pereira JM (2020) Spatial and temporal trends of burnt area in Angola: implications for natural vegetation and protected area management. Diversity 12, 307.
| Crossref | Google Scholar |

Chandler RE, Scott EM (Eds) (2011) ‘Statistical methods for trend detection and analysis in the environmental sciences’. (John Wiley & Sons: United Kingdom)

Copernicus Climate Change Service (2019) Fire danger indices historical data from the Copernicus Emergency Management Service. In ‘Copernicus Climate Change Service (C3S) Climate Data Store (CDS)’. (Copernicus Programme: Brussels, Belgium) 10.24381/cds.0e89c522. [verified 4 July 2024]

De Cauwer V, Mertens J (2018) Impact of fire on the Baikiaea woodlands. In ‘Climate Change and adaptive land management in southern Africa – assessments, changes, challenges, and solutions’. (Eds R Revermann, KM Krewenka, U Schmiedel, JM Olwoch, J Helmschrot, N Jürgens) pp. 334–335. (Biodiversity & Ecology, Klaus Hess Publishers: Windhoek) 10.7809/b-e.00342

Devine AP, McDonald RA, Quaife T, Maclean IM (2017) Determinants of woody encroachment and cover in African savannas. Oecologia 183, 939-951.
| Crossref | Google Scholar |

Dube OP (2009) Linking fire and climate: interactions with land use, vegetation, and soil. Current Opinion in Environmental Sustainability 1, 161-169.
| Crossref | Google Scholar |

Durbin J, Watson GS (1950) Testing for serial correlation in least squares regression. Biometrika 37, 409-428.
| Crossref | Google Scholar |

Eames T, Vernooij R, Russell-Smith J, Yates C, Edwards A, van der Werf GR (2023) Division of the tropical savanna fire season into early and late dry season burning using MODIS active fires. International Journal of Applied Earth Observation and Geoinformation 125, 103575.
| Crossref | Google Scholar |

Field RD, Spessa AC, Aziz NA, Camia A, Cantin A, Carr R, de Groot WJ, Dowdy AJ, Flannigan MD, Manomaiphiboon K, Pappenberger F, Tanpipat V, Wang X (2015) Development of a Global Fire Weather Database. Natural Hazards and Earth System Sciences 15, 1407-1423.
| Crossref | Google Scholar |

Gao Y, Huang W, Yu P, Xu R, Yang Z, Gasevic D, Ye T, Guo Y, Li S (2023) Long-term impacts of non-occupational wildfire exposure on human health: a systematic review. Environmental Pollution 320, 121041.
| Crossref | Google Scholar |

Geldenhuys CJ (1977) The effect of different regimes of annual burning on two woodland communities in Kavango. South African Forestry Journal 103, 32-42.
| Crossref | Google Scholar |

Giglio L, Boschetti L, Roy D, Hoffmann AA, Humber M, Hal JV (Eds) (2020) ‘Collection 6 MODIS Burned Area Product user’s guide version 1.3.’ (NASA EOSDIS Land Processes DAAC: Sioux Falls, USA)

Giglio L, Justice C, Boschetti L, Roy D (2021) MODIS/Terra+Aqua Burned Area Monthly L3 Global 500m SIN Grid V061 [Data set]. (NASA EOSDIS Land Processes Distributed Active Archive Center). 10.5067/MODIS/MCD64A1.061 [verified 4 August 2023]

Gignoux J, Lahoreau G, Julliard R, Barot S (2009) Establishment and early persistence of tree seedlings in an annually burned savanna. Journal of Ecology 97, 484-495.
| Crossref | Google Scholar |

Goss M, Swain DL, Abatzoglou JT, Sarhadi A, Kolden CA, Williams AP, Diffenbaugh NS (2020) Climate change is increasing the likelihood of extreme autumn wildfire conditions across California. Environmental Research Letters 15, 094016.
| Crossref | Google Scholar |

Grace J, Jose JS, Meir P, Miranda HS, Montes RA (2006) Productivity and carbon fluxes of tropical savannas. Journal of Biogeography 33, 387-400.
| Crossref | Google Scholar |

Harris LB, Taylor AH, Kassa H, Leta S, Powell B (2023) Humans and climate modulate fire activity across Ethiopia. Fire Ecology 19, 15.
| Crossref | Google Scholar |

Hersbach H, Bell B, Berrisford P, Biavati G, Horányi A, Muñoz Sabater J, Nicolas J, Peubey C, Radu R, Rozum I, Schepers D, Simmons A, Soci C, Dee D, Thépaut J-N (2023) ‘ERA5 hourly data on single levels from 1940 to present.’ (Copernicus Climate Change Service (C3S) Climate Data Store (CDS)). 10.24381/cds.adbb2d47 [verified 25 August 2023]

Hoffmann WA, Geiger EL, Gotsch SG, Rossatto DR, Silva LC, Lau OL, Haridasan M, Franco AC (2012) Ecological thresholds at the savanna–forest boundary: how plant traits, resources and fire govern the distribution of tropical biomes. Ecology Letters 15, 759-768.
| Crossref | Google Scholar |

Huntley BJ (Ed.) (2023) ‘Ecology of Angola: terrestrial biomes and ecoregions’. (Springer Nature: Cham, Switzerland)

Jain P, Castellanos-Acuna D, Coogan SC, Abatzoglou JT, Flannigan MD (2022) Observed increases in extreme fire weather driven by atmospheric humidity and temperature. Nature Climate Change 12, 63-70.
| Crossref | Google Scholar |

Kendall MG (Ed.) (1975) ‘Rank correlation methods’. (C. Griffin: London)

Krawchuk MA, Moritz MA (2011) Constraints on global fire activity vary across a resource gradient. Ecology 92, 121-132.
| Crossref | Google Scholar |

Kucharik CJ, Foley JA, Delire C, Fisher VA, Coe MT, Lenters JD, Young-Molling C, Ramankutty N, Norman J, Gower ST (2000) Testing the performance of a dynamic global ecosystem model: water balance, carbon balance, and vegetation structure. Global Biogeochemical Cycles 14, 795-825.
| Crossref | Google Scholar |

Laris P, Jacobs R, Koné M, Dembélé F, Rodrigue CM (2020) Determinants of fire intensity in working landscapes of an African savanna. Fire Ecology 16, 1-16.
| Crossref | Google Scholar |

Lawson BD, Armitage O (Eds) (2008) ‘Weather Guide for the Canadian Forest Fire Danger Rating System’. (Canadian Forest Service Northern Forestry Centre: Edmonton)

Levick SR, Baldeck CA, Asner GP (2015) Demographic legacies of fire history in an African savanna. Functional Ecology 29, 131-139.
| Crossref | Google Scholar |

Lipsett-Moore GJ, Wolff NH, Game ET (2018) Emissions mitigation opportunities for savanna countries from early dry season fire management. Nature Communications 9, 2247.
| Crossref | Google Scholar |

Liu Z, Eden JM, Dieppois B, Conradie WS, Blacket M (2023) The April 2021 Cape Town wildfire: has anthropogenic climate change altered the likelihood of extreme fire weather? Bulletin of the American Meteorological Society 104, 298-304.
| Crossref | Google Scholar |

Lopes D, Menezes I, Fernandes AP, Gama C, Sorte S, Reis J, Monteiro A, Borrego C, Miranda AI (2022) Smoke from extreme wildfire events and human health. Environmental Sciences Proceedings 17, 35.
| Crossref | Google Scholar |

Mann HB (1945) Nonparametric tests against trend. Econometrica 13, 245-259.
| Crossref | Google Scholar |

Moore NA, Camac JS, Morgan JW (2019) Effects of drought and fire on resprouting capacity of 52 temperate Australian perennial native grasses. New Phytologist 221, 1424-1433.
| Crossref | Google Scholar |

Murphy BP, Bowman DM (2012) What controls the distribution of tropical forest and savanna? Ecology Letters 15, 748-758.
| Crossref | Google Scholar |

NASA Earth Observation Data (2023) MCD64A1 v061MODIS/Terra+Aqua Burned Area Monthly L3 Global 500 m SIN Grid. NASA EOSDIS Land Processes DAAC. Available at https://lpdaac.usgs.gov/products/mcd64a1v061/ [verified 4 August 2023]

Neeti N, Eastman JR (2011) A contextual Mann-Kendall approach for the assessment of trend significance in image time series. Transactions in GIS 15, 599-611.
| Crossref | Google Scholar |

Nieman WA, Van Wilgen BW, Leslie AJ (2021) A review of fire management practices in African savanna-protected areas. Koedoe 63, a1655.
| Crossref | Google Scholar |

Olson DM, Dinerstein E, Wikramanayake ED, Burgess ND, Powell GV, Underwood EC, et al. (2001) Terrestrial ecoregions of the World: a new map of life on Earth: a new global map of terrestrial ecoregions provides an innovative tool for conserving biodiversity. BioScience 51, 933-938.
| Crossref | Google Scholar |

Otón G, Pereira JMC, Silva JM, Chuvieco E (2021) Analysis of trends in the fireCCI global long term burned area product (1982–2018). Fire 4, 74.
| Crossref | Google Scholar |

Pausas JG, Ribeiro E (2013) The global fire–productivity relationship. Global Ecology and Biogeography 22, 728-736.
| Crossref | Google Scholar |

Pearce HG, Moore JR (2004) Use of long-term fire danger data sets to predict fire season severity. Forest Research Client Report. (Fendalton, Christchurch)

Pereira JMC, Oom D, Pereira P, Turkman AA, Turkman KF (2015) Religious affiliation modulates weekly cycles of cropland burning in sub-Saharan Africa. PLoS One 10, e0139189.
| Crossref | Google Scholar |

Pereira JMC, Oom D, Silva PC, Benali A (2022) Wild, tamed, and domesticated: three fire macroregimes for global pyrogeography in the Anthropocene. Ecological Applications 32, e2588.
| Crossref | Google Scholar |

Perry JJ, Cook GD, Graham E, Meyer CM, Murphy HT, VanDerWal J (2019) Regional seasonality of fire size and fire weather conditions across Australia’s northern savanna. International Journal of Wildland Fire 29, 1-10.
| Crossref | Google Scholar |

Prichard SJ, Stevens-Rumann CS, Hessburg PF (2017) Tamm Review: shifting global fire regimes: lessons from reburns and research needs. Forest Ecology and Management 396, 217-233.
| Crossref | Google Scholar |

Pricope NG, Binford MW (2012) A spatio-temporal analysis of fire recurrence and extent for semi-arid savanna ecosystems in southern Africa using moderate-resolution satellite imagery. Journal of Environmental Management 100, 72-85.
| Crossref | Google Scholar |

Ratnam J, Bond WJ, Fensham RJ, Hoffmann WA, Archibald S, Lehmann CE, Anderson MT, Higgins SI, Sankaran M (2011) When is a ‘forest’ a savanna, and why does it matter? Global Ecology and Biogeography 20, 653-660.
| Crossref | Google Scholar |

Ripley B, Donald G, Osborne CP, Abraham T, Martin T (2010) Experimental investigation of fire ecology in the C3 and C4 subspecies of Alloteropsis semialata. Journal of Ecology 98, 1196-1203.
| Crossref | Google Scholar |

Russell-Smith J, Murphy BP, Meyer CM, Cook GD, Maier S, Edwards AC, Schat J, Brocklehurst P (2009) Improving estimates of savanna burning emissions for greenhouse accounting in northern Australia: limitations, challenges, applications. International Journal of Wildland Fire 18, 1-18.
| Crossref | Google Scholar |

Russell-Smith J, Cook GD, Cooke PM, Edwards AC, Lendrum M, Meyer CP, Whitehead PJ (2013) Managing fire regimes in north Australian savannas: applying Aboriginal approaches to contemporary global problems. Frontiers in Ecology and the Environment 11, e55-e63.
| Crossref | Google Scholar |

Russell-Smith J, Yates C, Vernooij R, Eames T, van der Werf G, Ribeiro N, Edwards A, Beatty R, Lekoko O, Mafoko J, Monagle C, Johnston S (2021) Opportunities and challenges for savanna burning emissions abatement in southern Africa. Journal of Environmental Management 288, 112414.
| Crossref | Google Scholar |

Sankaran M (2019) Droughts and the ecological future of tropical savanna vegetation. Journal of Ecology 107, 1531-1549.
| Crossref | Google Scholar |

Sen PK (1968) Estimates of regression coefficient based on Kendall’s tau. Journal of the American Statistical Association 63, 1379-1389.
| Crossref | Google Scholar |

Silva JMN, Moreno MV, Le Page Y, Oom D, Bistinas I, Pereira JMC (2019) Spatiotemporal trends of area burnt in the Iberian Peninsula, 1975–2013. Regional Environmental Change 19, 515-527.
| Crossref | Google Scholar |

Silva PS, Rodrigues JA, Santos FL, Nogueira J, Pereira AA, Peres LF, Oom, D, Da Camara CC, Pereira JMC, Libonati R (2020) Burned area trends in the Brazilian Cerrado: the roles of climate and anthropogenic drivers (No. EGU2020-20907). (Copernicus Meetings) 10.5194/egusphere-egu2020-20907

TerrSet (2020) Geospatial monitoring and modeling system. Clark Labs. Available at https://clarklabs.org/wp-content/uploads/2020/05/TerrSet_2020_Brochure-FINAL27163334.pdf [verified 18 August 2023]

Theil H (1950) A rank-invariant method of linear and polynomial regression analysis. Indagationes Mathematicae 12, 173.
| Google Scholar |

van der Werf GR, Randerson JT, Giglio L, Gobron N, Dolman AJ (2008) Climate controls on the variability of fires in the tropics and subtropics. Global Biogeochemical Cycles 22, GB3028.
| Crossref | Google Scholar |

van Wagner CE (Ed.) (1974) ‘Structure of the Canadian Forest Fire Weather Index’. (Environment Canada, Forestry Service: Alberta, Canada)

van Wagner CE (1987) ‘Development and structure of the Canadian Forest Fire Weather Index system.’ Forestry Technical Report. (CFS - Ottawa).

van Wees D, van der Werf GR, Randerson JT, Rogers BM, Chen Y, Veraverbeke S, Giglio L, Morton DC (2022) Global biomass burning fuel consumption and emissions at 500 m spatial resolution based on the Global Fire Emissions Database (GFED). Geoscientific Model Development 15, 8411-8437.
| Crossref | Google Scholar |

Venäläinen A, Korhonen N, Hyvärinen O, Koutsias N, Xystrakis F, Urbieta IR, Moreno JM (2014) Temporal variations and change in forest fire danger in Europe for 1960–2012. Natural Hazards and Earth System Sciences 14, 1477-1490.
| Crossref | Google Scholar |

Vernooij R, Giongo M, Borges MA, Costa MM, Barradas ACS, van der Werf GR (2021) Intraseasonal variability of greenhouse gas emission factors from biomass burning in the Brazilian Cerrado. Biogeosciences 18, 1375-1393.
| Crossref | Google Scholar |

Vernooij R, Eames T, Russell-Smith J, Yates C, Beatty R, Evans J, Edwards A, Ribeiro N, Wooster M, Strydom T, Giongo MV, Borges MA, Menezes Costa M, Barradas ACS, van Wees D, van der Werf GR (2023) Dynamic savanna burning emission factors based on satellite data using a machine learning approach. Earth System Dynamics 14, 1039-1064.
| Crossref | Google Scholar |

Viegas DX, Bovio G, Ferreira A, Nosenzo A, Sol B (1999) Comparative study of various methods of fire danger evaluation in southern Europe. International Journal of Wildland Fire 9, 235-246.
| Crossref | Google Scholar |

Wang XLL, Swail VR (2001) Changes of extreme wave heights in Northern Hemisphere oceans and related atmospheric circulation regimes. Journal of Climate 14, 2204-2221.
| Crossref | Google Scholar |

Zomer RJ, Xu J, Trabucco A (2022) Version 3 of the global aridity index and potential evapotranspiration database. Scientific Data 9, 409.
| Crossref | Google Scholar |

Zubkova M, Boschetti L, Abatzoglou JT, Giglio L (2019) Changes in fire activity in Africa from 2002 to 2016 and their potential drivers. Geophysical Research Letters 46, 7643-7653.
| Crossref | Google Scholar |