"Amazonian dark earth" was the work of ancient humans
Ancient “Amazonian dark earth” (terra preta) is increasingly seen as a human-made soil created by pre-Columbian societies using charcoal, organic waste, and pottery shards to dramatically boost fertility and lock away carbon for centuries. Commenters connect this to modern biochar research, highlighting its potential as a long-lived soil amendment and carbon-negative climate tool, while trading practical tips for DIY biochar in gardens. The conversation also touches on how these findings reshape views of Amazonian and broader Indigenous civilizations, suggesting dense, sophisticated societies that largely vanished after European-introduced diseases.
Prior knowledge and significance of Amazonian dark earth
- Multiple commenters note that terra preta/Amazonian dark earth has been studied for decades and featured in popular books on pre‑Columbian Americas.
- Some found the BBC piece light on new substance; others said ADE’s scale and implications were new and fascinating to them.
- Expectation that LIDAR and other tech will reveal many more Amazonian sites, as with other river-basin civilizations.
What biochar is and its effects
- Biochar is described as charcoal produced by low‑oxygen pyrolysis of biomass, often later “loaded” with nutrients.
- It is strongly framed as carbon‑negative: wood that would rot to CO₂/methane instead becomes stable carbon in soil for decades–centuries.
- Cited benefits: improved soil structure and drainage, higher nutrient retention, better microbial activity, reduced fertilizer and water needs.
- Some uncertainty remains about the exact mechanisms and whether benefits occur without significant decomposition of the carbon itself.
DIY and practical use
- Gardeners discuss making biochar with pit or cone fires: burning wood in low oxygen, quenching early, then crushing and mixing with compost or manure.
- Strong advice: don’t add fresh char straight to soil; pre‑charge it in compost so it doesn’t initially strip nutrients.
- Suggestions to use grass clippings or purchased nitrogen sources to load biochar; also to use compost piles or trench composting for general soil improvement.
Formation and nature of terra preta
- One view: ADE results from centuries of villagers concentrating food scraps, feces, ash, pottery, bones, and other organic waste near fields.
- Others stress the role of deliberate charcoal production and note characteristic components (char, pottery shards, manures) as more than random dumping.
- There is mention that ADE can “spread” its beneficial properties when mixed into surrounding poor soils, though details are unclear.
Ancient Amazonian societies and collapse
- Links to ruins and early European travel accounts support the idea of dense, organized Amazonian polities whose remains vanished due to perishable materials and jungle overgrowth.
- Commenters frame many present-day forest peoples as descendants of post‑collapse societies, paralleling arguments about “fringe” hunter‑gatherers globally.
Colonization, disease, and genocide debate
- Strong disagreement over estimates (tens of millions dead) and language around a “great dying.”
- One side emphasizes disease-driven 90%‑level mortality, climate impacts, and systemic dispossession and extermination policies.
- Another side questions intent, scale, and characterizations of deliberate genocide, and stresses complex, two‑way conflict and alliances.
- Consensus only that disease, conquest, and policy together produced catastrophic demographic collapse.
Human impact on ecosystems
- Several comments argue humans can be net‑beneficial ecosystem engineers (ADE, forest gardening).
- Others counter that modern industrial agriculture annihilates surrounding life via pesticides and monoculture, unlike more integrated systems (with comparisons to ants’ farming behaviors).