Madagascar's fire regimes challenge global assumptions about landscape degradation

Fire and environmental dataset (2003 - 2019) for Phelps et al. (2022,
Global Change Biology). Associated manuscript abstract: Narratives of
landscape degradation are often linked to unsustainable fire use by local
communities. Madagascar is a case in point: the island is considered
globally exceptional, with its remarkable endemic biodiversity seen as
threatened by unsustainable anthropogenic fire. Yet, fire regimes on
Madagascar have not been empirically characterised or globally
contextualised. Here, we apply a comparative approach using MODIS remote
sensing data (2003-2019), to determine relationships between Madagascar’s
fire regimes and global patterns and trends. We demonstrate that
Madagascar’s fire regimes are similar to 88% of tropical burned area, with
shared climate and vegetation characteristics. Therefore, rather than a
global exception, Madagascar’s fire regimes could usefully be understood
as a microcosm of most tropical fire regimes, which contribute to global
understanding of fire. We found that landscape-scale fire declined in
grassy biomes across the tropics, and at a relatively fast rate on
Madagascar. The island’s high tree loss anomalies (1.25 to 4.77x the
tropical average) were not explained by any general expansion of grassy
biome burning and were centred in forests rather than at forest-savanna
boundaries, demonstrating that high rates of forest degradation were not
explained by landscape-scale fire escaping from savannas into forests.
Associated with forests, landscape-scale fire trends reflected important
differences among tropical regions, indicating a need to better understand
regional variation in the anthropogenic drivers of change. Unexpectedly,
the highest tree loss anomalies on Madagascar were centred in environments
without landscape-scale fire, where the role of small-scale fires
(<21ha) is unknown. Madagascar’s fire regimes thus contribute two
lessons with global implications: first, landscape-scale burning is
declining in grassy biomes across the tropics and does not explain high
tree loss anomalies on Madagascar. Second, landscape-scale fire is not
uniformly associated with forest loss, indicating a need for more
socio-ecological context around narratives of tropical fire and ecosystem
degradation.