A large Amazon forest area is needed to recycle atmospheric water by transpiration, causing cooling, air movement and rainfall that help maintain the forest.
Deforestation lowers transpiration and rainfall, increases drying and fire risk, and fragments habitat; further forest loss can then reinforce the original change. The minimum area needed to maintain these processes remains uncertain.
The mapped local textbook reports 3,399,308 km² in 2017 and 3,390,835 km² in 2018: ((3,390,835 − 3,399,308) ÷ 3,399,308) × 100 = −0.25%, so estimated cover fell by 0.25%.
A proposed tipping range is uncertain, so a calculated percentage loss must not be presented as proof that an irreversible threshold has already been crossed.