Amazon tipping-point model sets its threshold at 1.5 degrees and 22% deforestation

A moist tropical forest is rarely flammable. Bernardo Flores draws the distinction this way: forest fires, in his usage, are the ones that penetrate and spread through moist forest, and in dry El Nino years thousands of kilometers of forest that had not been disturbed before have burned ^[5][6]. Flores is a Brazilian ecologist working in the Equalsea-lab at the University of Santiago de Compostela, and his research covers Amazon fire ecology and tipping points ^[4]. El Nino itself is the warm phase of a multiyear natural cycle, and it tends to arrive with rising global temperatures and disruptive weather ^[19].

The loop he describes runs through rain. Lose enough forest and the basin loses enough rain that the system becomes trapped in a self-degrading drought-fire loop ^[10]. Flores said global warming is basically at the level his model uses, which means one of the two conditions in his own threshold is already described as met ^[9][1]. Flores did not give a current figure for cumulative deforestation across the basin, so the distance to the second condition is not on the record ^[20].

The threshold counts deforestation only. Flores said the model does not consider the forest degradation accumulated over past decades, a quantity separate from the deforestation the threshold counts ^[11]. In a recent paper, he and colleagues wrote that the Amazon could undergo a "near systemwide transition" ^[18].

Flores's account of a crossing takes in people as well as climate. Indigenous people and local communities who protect and manage the forest are, in his description, one of the things that makes the Amazon resilient ^[13]. Add drought, fire, and water and food insecurity from these El Ninos, he said, and the risk rises that those regions are abandoned and become easier for organized crime groups to occupy through methods that involve destruction and fires ^[15].

The signal he points to is a rate of increase. Flores said burnt areas are expected to increase, possibly exponentially: "There will be an acceleration, and that's a sign of a tipping point" ^[7]. An acceleration is measured between years, so it takes at least two seasons of burnt-area data to evaluate, and one season's total will not settle whether the basin has crossed anything ^[2]. Flores said, "I have been saying that we could cross a tipping point," and, "This is a very concerning and critical moment to focus on wildfires" ^[16][17].