School of GeoSciences, University of Edinburgh, Edinburgh, UK.
Tropical Diversity, Royal Botanic Garden Edinburgh, Edinburgh, UK.
Glob Chang Biol. 2022 Dec;28(23):6944-6960. doi: 10.1111/gcb.16206. Epub 2022 May 18.
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 viewed as threatened by unsustainable anthropogenic fire. Yet, fire regimes on Madagascar have not been empirically characterised or globally contextualised. Here, we contribute a comparative approach to determining relationships between regional fire regimes and global patterns and trends, applied to Madagascar using MODIS remote sensing data (2003-2019). Rather than a global exception, we show that Madagascar's fire regimes are similar to 88% of tropical burned area with shared climate and vegetation characteristics, and can be considered a microcosm of most tropical fire regimes. From 2003-2019, landscape-scale fire declined across tropical grassy biomes (17%-44% excluding Madagascar), and on Madagascar at a relatively fast rate (36%-46%). Thus, high tree loss anomalies on the island (1.25-4.77× the tropical average) were not explained by any general expansion of landscape-scale fire in grassy biomes. Rather, tree loss anomalies centred in forests, and could not be explained by landscape-scale fire escaping from savannas into forests. Unexpectedly, the highest tree loss anomalies on Madagascar (4.77×) occurred in environments without landscape-scale fire, where the role of small-scale fires (<21 h [0.21 km ]) is unknown. While landscape-scale fire declined across tropical grassy biomes, trends in tropical forests reflected important differences among regions, indicating a need to better understand regional variation in the anthropogenic drivers of forest loss and fire risk. Our new understanding of Madagascar's fire regimes offers two lessons with global implications: first, landscape-scale fire is declining across tropical grassy biomes and does not explain high tree loss anomalies on Madagascar. Second, landscape-scale fire is not uniformly associated with tropical forest loss, indicating a need for socio-ecological context in framing new narratives of fire and ecosystem degradation.
景观退化的叙述常常与当地社区不可持续的火灾利用有关。马达加斯加就是一个典型的例子：该岛被认为在全球范围内是独一无二的，其显著的特有生物多样性被认为受到不可持续的人为火灾的威胁。然而，马达加斯加的火灾模式尚未经过实证描述或全球背景化。在这里，我们采用比较方法来确定区域火灾模式与全球模式和趋势之间的关系，应用于使用 MODIS 遥感数据（2003-2019 年）的马达加斯加。我们展示的结果并不是全球的例外，而是表明马达加斯加的火灾模式与 88%的热带燃烧面积具有相似的气候和植被特征，可以被视为大多数热带火灾模式的缩影。从 2003 年到 2019 年，热带草原生物群落的景观规模火灾减少了（不包括马达加斯加为 17%-44%），而在马达加斯加则以相对较快的速度减少（36%-46%）。因此，岛上树木损失异常高（热带平均水平的 1.25-4.77 倍）并不能用草原生物群落中景观规模火灾的普遍扩大来解释。相反，树木损失异常集中在森林地区，不能用从稀树草原逃到森林的景观规模火灾来解释。出乎意料的是，马达加斯加的树木损失异常最高（4.77 倍）发生在没有景观规模火灾的环境中，而小尺度火灾（<21 小时[0.21 公里]）的作用尚不清楚。虽然热带草原生物群落的景观规模火灾减少了，但热带森林的趋势反映了不同地区之间的重要差异，表明需要更好地了解森林损失和火灾风险的人为驱动因素的区域变化。我们对马达加斯加火灾模式的新认识有两个具有全球意义的教训：首先，热带草原生物群落的景观规模火灾正在减少，这并不能解释马达加斯加树木损失异常高的原因。其次，景观规模火灾与热带森林的损失并不完全相关，这表明在构建新的火灾和生态系统退化叙事时需要考虑社会生态背景。
