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São Félix do Xingu: 232.05 ha of forest loss flagged in 90 days, NDVI confirms

São Félix do Xingu (PA) · seen · published

Between 28 June and 26 September 2026, satellite alert systems logged 18977 high-confidence deforestation alerts inside the São Félix do Xingu (PA) area of interest, covering 232.05 ha. Of that, 223 ha came from high-confidence alerts and 9.05 ha from the highest-confidence class. An independent optical check backs this up: median-composite Sentinel-2 NDVI — a greenness measure — fell by -0.133 over roughly the same window, with 93% and 96% of pixels usable in the two composites, so cloud is not driving the result.

What this is not: the alerts cannot tell legal clearing, fire, storm damage or selective logging apart from unauthorised clearing, and no cause is assigned here. This is an El Niño season (ONI 1.8), when drought stress alone can lower greenness. Regrowth and harvest cycles can also mimic loss. Notably, alert density here is 0.501× that of the surrounding 25 km ring — this block is quieter than its neighbourhood.

What would change our mind: higher-resolution imagery showing intact canopy, burn-scar mapping indicating fire, concession or protected-area layers placing the change in a managed cycle, or an NDVI rebound in the next composite.

Written by AI, then checked by a separate reviewer before publication. Every claim points at the evidence below.

Cloud-free satellite view around São Félix do Xingu (PA), with the finding area outlined
6.65°S 52.15°WNASA Blue Marble via GIBS · outline = finding area

What we saw

  • Area: 232 hectares — about 330 football fields
  • Global Forest Watch alerts — 18977 alerts (≥ high confidence), 232.05 ha, 2026-06-28…2026-09-26. (Sep 26, 2026) See the source ↗
  • Sentinel-2 satellite images — Median-composite NDVI changed -0.133 (2026-05-14 → 2026-09-26); valid pixels 93% / 96%. Scenes: [object Object], [object Object], [object Object], [object Object], [object Object], [object Object] (Sep 26, 2026)

What it might not be

  • Alerts lag events by about 1–2 weeks, so a recent burst may be undercounted.
  • Fire, storm damage, selective logging and legal clearing are not separable from this data alone.
  • El Niño (ONI 1.8) drought can depress NDVI without canopy removal.
  • Regrowth and plantation harvest cycles can resemble loss; the 25 km baseline ring only partly compensates.
  • Alert coverage is 30°N–30°S only; absence of alerts elsewhere means unmonitored, not unchanged.
  • Coverage is 30°N–30°S only — zero alerts outside the tropics means 'not monitored', not 'no loss'.
  • Cannot distinguish legal clearing, fire, storm damage and selective logging from illegal clearing; attribution needs concession/protected-area layers (M3).
  • Alerts lag reality by ~1–2 weeks; a burst just before the sweep is undercounted.
  • Regrowth and plantation harvest cycles look like loss; the baseline ring only partly compensates.
  • Persistent cloud can delay optical confirmation for months (SAR-only RADD alerts stay 'candidate').

What would change our mind

Newer satellite images that show no change, a correction from the data source, or a reply with evidence from the ground. If that happens, the case is marked “Turned out wrong” — in public — and it stays on this site.

Why this was published

Two separate sources agreed — Global Forest Watch alerts, then Sentinel-2 satellite images — and a reviewer checked the evidence before it went up.

Right of reply

If a case names or affects you, you can reply. A reply channel that keeps both sides on record is being set up; until then, every case page carries its ledger id so a reply can be attached to it.

Ledger id 01a0deea-0484-7e03-bd7e-b887aad6053d

Technical details rule, evidence ids, history, proof
Rule
forest_loss v1.0
Tier
T1
Tags
amazon, brazil, cattle-frontier
Confirmed
Yes — independent sensor signal, 2026-09-26
Rule FP rate
50 % · 2 of 4 decided
Location
6.65°S 52.15°W
Observed
2026-09-26
Opened
2026-09-26 by automatic rule forest_loss v1.0
  1. candidate
  2. confirmed
  3. published
  4. resolved

Evidence2

alertgfw-integrated-alerts

18977 alerts (≥ high confidence), 232.05 ha, 2026-06-28…2026-09-26.

alerts 18977ha 232.05high_alerts 18237high_ha 223highest_alerts 740highest_ha 9.05
· forest_alerts v1.0 · gfw-integrated-br-sao-felix-do-xingu-2026-06-28..2026-09-26
Source ↗
scenesentinel-2-l2aConfirming signal

Median-composite NDVI changed -0.133 (2026-05-14 → 2026-09-26); valid pixels 93% / 96%. Scenes: [object Object], [object Object], [object Object], [object Object], [object Object], [object Object]

deltaNdvi -0.13307291321656778validPctA 93validPctB 96
· eo_compare v1.0 · s2-ndvi-median-br-sao-felix-do-xingu-2026-05-14..2026-09-26

Context

0.50×
AOI vs its 25 km neighbourhood
AOI
928.2
Ring
1854.333
Metric
alert ha per deg²
ENSO El Niño · ONI +1.8

Publication gates

  • Evidence — 1 piece from gfw-integrated-alerts — met
  • Independent confirmation — a different sensor (sentinel-2-l2a), 2026-09-26 — met
  • Human approval — 1 of 1 needed at tier 1 — met
  • Narration — AI-drafted by claude-opus-5 — met
Published
2026-09-26 by AI model
Narrated By
AI model
Reviewed By
AI model
Policy
2026-09-26-autonomous
Note
autonomous publish: narrated by model:claude-opus-5, reviewed by model:claude-sonnet-5 (policy 2026-09-26-autonomous)

History5

  1. status changed → publishedAI model
  2. reviewed → confirmedAI model
  3. narrated → confirmedAI model
  4. confirmed → confirmedautomatic rule forest_loss v1.0
  5. created → candidateautomatic rule forest_loss v1.0

Verify

Checkpoint
earthdeck.dev/findings/v1 · 23 entries
Signed root
98f501ea7b18…03d8f3
This case
5 signed events
Leaf
#14 of 23 — this case’s latest event
Leaf hash
a0e5d05829d5…83f4e3
Proof
5-hash audit path
  1. 1e611eff0173e26ac4ddb44745a44b6c640dd39a5e6140a128a512256b97abc7
  2. 3fd4e2b4cab4c16e695df31947d9d7e4ed7a376cee835d9b3936c7357ef03e18
  3. 401048d1bf40798f07496286641f8cb62e8a3d4bf5582987af3fbcd0526da7a4
  4. 26fb30453e28c43d71f1119e5e1add72de6b3c28c1202a557be9ab963856f5d7
  5. 4a353bd4228873504ddacce3976e700a8f44051505c8db4cdd55e1d387e08c25
Last event
06aa8dae5e66…1dd929
Note
Checkpoint text
earthdeck.dev/findings/v1
23
mPUB6nsYl6cXwueotNRJ80TfqTTMx5TVtGhn118D2PM=

— earthdeck TkCXv+gZUFrKQuTIDCzT//Iq9xayLZfvnv5RpOdRIxrlavfIeuQLP1bP0LmnSltfP2nqDAADjxr7nksOwDgNrIZCXwc=

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