Non fire-adapted dry forest of Northwestern Madagascar: escalating and devastating trends revealed by remote-sensing data

  1. Joseph Emile Honour Percival
  2. Hiroki Sato
  3. Tojotanjona Patrick Razanaparany
  4. Ando Rakotomamonjy Harilalao
  5. Zo Lalaina Razafiarison
  6. Kaoru Kitajima

Reviewed by

Read the full article See related articles

Listed in

Log in to save this article

Abstract

Ankarafantsika National Park (ANP), the last significant remnant of Northwestern Madagascar’s tropical dry forests, is facing rapid degradation due to increased incidences of fire. This poses severe threats to biodiversity, local livelihoods, and vital ecosystem services. Our study, conducted on 3052 ha of ANP’s pristine forests, employed advanced remote-sensing techniques to assess fire impacts during the past 37 years. Our aims were to understand historical fire patterns and evaluate forest recovery and susceptibility to repeated fires following initial burns. Using data from multiple Landsat satellite sensors, we constructed a time series of fire events since 1985, which revealed no fire activity before 2014. The Global Ecosystem Dynamics Investigation (GEDI) lidar sensor data were used to observe forest structure in both post-fire areas and undisturbed zones for comparison. We recorded six fire incidents from 2014-2021, during which the fire-affected area exponentially grew. A significant fire incident in October 2021 impacted 1052 hectares, 59% of which had experienced at least one fire in 2-4 years prior, with 60% experiencing 2 preceding incidents: one in 2017 and another in 2019. The initial fire drastically reduced plant cover and tree height, with subsequent fires causing minor additional loss. Post-fire recovery was negligible within the initial four years, even in patches without recurrent fires. The likelihood for an initial burn to trigger subsequent fires within a few years was high, leading to larger, more severe fires. We conclude that ANP’s dry forests exhibit high vulnerability and low resilience to anthropogenic fires. Prompt preventive measures are essential to halt further fire spread and conserve the park’s unique and invaluable biodiversity.

Article activity feed

  1. PREreview

    This Zenodo record is a permanently preserved version of a PREreview. You can view the complete PREreview at https://prereview.org/reviews/10719612.

    This paper studies at Ankarafantsika National Park (ANP) in Madagascar that has historically, from 1985-present, lacked wildfire activity. Globally, a combination of natural and human factors has led to an increase in fire frequency, severity, and extent of fires in dry forests and savannahs. Frequent human-caused fires in the dry forests of Madagascar may lead dry forests to transition into grasslands and savannahs, though the cause of forest degradation has not been linked to fire. The goal of this study was to understand historical fire patterns in the region and evaluate forest recovery and vulnerability post-fire. Using remote sensing data, the authors monitor past fire patterns and determine if new fires promote future fire activity.  Using Landsat data from the past 37 years, researchers used Normalized Difference Vegetation Index (NDVI) and Differenced Normalized Burn Ratio (dNBR) to analyze fire scars beginning in 2014. Next, they determined how many burn events occurred on an area since the initial burn. While areas adjacent to ANP have a longer history of fire activity, the park itself lacks a consistent fire regime. With the threat of increasing wildfire introduced to the park, it is critical to prepare for changes that may occur within park boundaries. The authors clearly state the need for additional research to determine how fire affects community composition in ANP. More research is needed on how to prevent fires and to inform management strategies to mitigate the threat of increasing wildfire. Home to multiple endemic species of lemurs, reptiles, and birds, ANP serves as a biological hotspot and research is critical for biological conservation. 

    Strengths

    • The authors list clear objectives for their study  

    • The authors justify their study by mentioning that fire has not yet been proven to be a proxy for forest degradation.  

    • The results are divided into two sections: fire records from 1985 to 2022 and fire impacts on forest structure.  

    • They list clear directions and questions for future studies. 

    Major issues

    Mention/discuss fire history prior 1985 – The paper includes fire history from 1985 to 2022 but does not mention prior fire history. We think the paper would benefit from a short discussion on fire history before 1985. For example, has this area always been forested? Was fire suppression used within the park, leading the forest to become non-fire adapted? Did this landscape have a natural fire regime prior to human intervention? Have you considered that this was at once a dry fire adapted forest, but due to fire suppression it is more prone to severe burns and hence will not recover as well? We understand that research and data may be lacking regarding fire history before 1985, but a brief mention of this may justify why the authors did not include prior history.  

    Minor issues

    • Main Body – the word "savanna" is used interchangeably with "savannah." Although both are correct, we suggest using one spelling ("savannah" is used in many varieties of English).  

    • Line 62 – the authors mention that Madagascar has "seen an average of over 350,000 fires annually between 2012 and 2019" which cites a paper by Frappier-Brinton and Lehman. To avoid confusion, we suggest defining what a fire is in this context. For example, mention that these fires varied in scale/intensity, but all have the potential to affect nearby dry forests due to their close proximity.  

    • Line 95 – Florida is mentioned as an example to illustrate that firs can vary within short distances of a topographical gradient. We suggest that the authors describe why Florida was used as an example in this context. Are the dry forests and savannahs of Florida similar to those in Madagascar? We also suggest adding additional examples from other regions of the world to further illustrate this point.  

    • Line 218 – The statement that population growth has increased demand for food and energy resources could benefit by a citation. Is there a journal article or other source that mentions population growth and effects in Madagascar?  

    • Line 240 – We suggest writing out the location (Central Menabe, Madagascar) then adding the citation. For example, "Whereas the study [14] in Central Menabe, Madagascar consisted of dark..."  

    • Lines 335-336 – Consider mentioning NDVI and dNBR instead of waiting until the second paragraph of the next section. 

    • Line 321 – The fire regime inside the park is mentioned as "low and variable." We suggest adding more detail. For example, how frequent and intense are these fires? What makes them variable?  

    • Figure 1 – image D is not high quality. Consider increasing the resolution of this image if possible. Also, the figure does not include a legend describing what the colors in images B, C, and D mean. The figure description mentions that these are maps of the study area. Do the dark green colors refer to forested areas? What about the purple areas? We understand that there are many colors, but a description of large color patches can be helpful for interpretation. Consider adding a legend.  

    • Figure 2 panel B – the x-axis stops at 2015, making it difficult to distinguish which bar relates to which year. Consider adding 2020 here to make the graph clearer.  

    Competing interests

    The authors declare that they have no competing interests.

  2. Version published to 10.1101/2023.09.12.557329v1 on bioRxiv