Data from: Forest extent and deforestation in tropical Africa since 1900

Accurate estimates of historical forest extent and associated deforestation rates are crucial for quantifying tropical carbon cycles and formulating conservation policy. In Africa, data-driven estimates of historical closed-canopy forest extent and deforestation at the continental scale are lacking, and existing modelled estimates diverge substantially. Here, we synthesize available palaeo-proxies and historical maps to reconstruct forest extent in tropical Africa around 1900, when European colonization accelerated markedly, and compare these historical estimates with modern forest extent to estimate deforestation. We find that forests were less extensive in 1900 than bioclimatic models predict. Resultantly, across tropical Africa, ~ 21.7% of forests have been deforested, yielding substantially slower deforestation than previous estimates (35–55%). However, deforestation was heterogeneous: West and East African forests have undergone almost complete decline (~ 83.3 and 93.0%, respectively), while Central African forests have expanded at the expense of savannahs (~ 1.4% net forest expansion, with ~ 135,270 km2 of savannahs encroached). These results suggest that climate alone does not determine savannah and forest distributions and that many savannahs hitherto considered to be degraded forests are instead relatively old. These data-driven reconstructions of historical biome distributions will inform tropical carbon cycle estimates, carbon mitigation initiatives and conservation planning in both forest and savannah systems.

精准估算历史森林覆盖范围及其伴随的森林砍伐速率，对于量化热带碳循环、制定保护政策至关重要。在非洲大陆尺度上，目前仍缺乏基于数据驱动的历史郁闭林（closed-canopy forest）覆盖范围与森林砍伐速率的估算结果，且现有模型估算结果存在显著分歧。本研究整合现有古代用指标（palaeo-proxies）与历史地图，重建欧洲殖民化显著加速的1900年前后热带非洲的森林覆盖范围，并将这些历史估算结果与现代森林覆盖范围进行对比以估算森林砍伐情况。研究发现，1900年时的森林覆盖范围小于生物气候模型的预测值。据此，整个热带非洲已有约21.7%的森林遭到砍伐，森林砍伐速率显著低于此前估算的35%至55%。但森林砍伐存在显著的区域异质性：西非与东非的森林几乎已完全衰退（分别约为83.3%和93.0%），而中非森林则以稀树草原为代价实现了扩张——森林净扩张率约为1.4%，有约13.527万平方千米的稀树草原被侵占。这些研究结果表明，仅靠气候无法决定稀树草原与森林的分布格局，且诸多此前被认定为退化森林的稀树草原，实则为相对古老的原生植被。这些基于数据驱动的历史生物群系（biome）分布重建结果，将为热带碳循环估算、碳减排举措以及森林与稀树草原系统的保护规划提供科学依据。