Chapter · Brazil · Today
Watching a forest by satellite
How a country measures what it loses, and publishes the figure
Since 1988 Brazil has measured each year the Amazon forest it has lost, and published the result. This path does not argue with the figure: it reads the technical notes of the institute that produces it, and looks at what the number is made of.
Context first
A lesson to read before the others, to set the scene.
- The place
- The era
- The people
The lessons in this chapter
- 1Six and a quarter hectaresThe threshold of the Amazon statistic comes from tracing paper laid on a 1:250,000 print in 1988. It is worth a millimetre of pencil, it leaves ten thousand km² of clearings outside, and it is kept on purpose.10 min
- 2Two hundred and seventy-one tilesA figure for five million km², calculated over a little more than half the territory, tested by three thousand simulations, and corrected against itself where clouds blocked the view.10 min
- 3Who checks the checkerAn institute’s defence is worth only as much as whoever checked it: here an outside laboratory, an international protocol, 1,495 points, 98.8% plus or minus 0.4, and an 88% published along with the rest.10 min
How these lessons are written
Each lesson starts from first-hand sources: Wikisource, Gallica, Persée, archives, museums and institutes. A fact without a source does not get written, and every lesson lists its own as direct links.
The rhythm
A lesson is five minutes of cards and four questions. Those questions then come back the next day, then at 3, 7, 21 and 60 days, and that return is what makes it stick. One a day is enough, and you can do several in a row.