Three-quarters of the Amazon rainforest may be speeding toward a “tipping point” that, if passed, could leave the world’s critical tropical biome a relatively dry savanna within a few decades, according to new research published today in the journal Nature Climate Change.
For years, researchers have been using complex models to predict when the region will cross this threshold. What’s new about this research is its reliance on satellite data to measure changes in how quickly the forests bounce back after drought, fire or human activity. Amazon has a significant role to play in regional and global climate systems. It is responsible for redistributing water throughout South America and helping preserve biodiversity.
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The new paper’s authors, from the University of Exeter and the Technical University of Munich, examined the forest’s rate of recovery from disruptive events—mostly drought and human activity—a factor they call “resilience.” They analyzed two kinds of data, one that estimates tree water content by sensing biomass levels, and another that records how green vegetation is. Twenty years of satellite data was enough for them to conclude that the forests’ response rate has worryingly declined in just two decades—but not enough to say with any precision when the Amazon might cross the tipping point.
The “system is losing stability,” said Timothy Lenton, director of the Global Systems Institute at the University of Exeter and a co-author. “What’s important is, it can be losing stability, and we can pick that signal up—without it necessarily showing up as some really massive change in the biomass or the tree cover.”
Timeline projections are difficult because of other challenges than the analysis. “It’s going to depend on defining what counts as catastrophe,” he said. This could be a way to identify a certain percentage of forest destruction. For example, he said, if enormous conflagrations informally called “mega fires” pick up, “you could lose a significant chunk of it in the space of a decade or two.”
Lenton and others have discovered what they believe to be a range of tipping points. These are the limits beyond which major Earth system could change their operation. This includes melting polar and other glaciers, melting permafrost, and ecosystem shifts like coral die-off and forests.
It is millions of year old. Ice ages caused by the Earth’s orbital variations came and went, rainfall rose and fell and its boundaries shifted with time. “It has always survived this,” said Niklas Boers, an Earth system modeling professor at the Technical University of Munich and a co-author. In all that time, not one species of tree has actively degraded vast forests and rendered the world more vulnerable to drought. “There’s no point back in time where we can say that the situation is like this.”
The main cause of climate changes is deforestation. According to research, stopping the deforestation helps keep the Amazon’s local areas healthy and also improves the health of all of Amazon.
In a UN climate science report of 3,675 pages, the threat to tropical forests was given its own section. With 4.2 million square kilometers (1.6 million square miles) of forests lost since 1990—90% of it in the tropics—the scientists concluded that “the complexity of tackling drivers of forest loss and degradation is increasing as climate impacts on forests and ecosystems increase.”
Boers said that there’s still time to work urgently to slow or stop the damage. “We haven’t crossed that tipping point yet,” he said. “So there’s still hope.”
