There’s a great scene in West Wing about a fire in Yellowstone. “When something catches on fire, it’s no longer out policy to put it out?”
The scene was based off a real incident of fire management strategy. In 1988, Yellowstone suffered the largest wildfire recorded in it’s history, burning 30% of the total acreage of the park. The fires called into question the National Park Service’s “let it burn” strategy.
Implemented in 1972, this policy let natural fires run their course and remains policy today. As per a 2008 order from the director of the National Park Service, “Wildland fire will be used to protect, maintain, and enhance natural and cultural resources and, as nearly as possible, be allowed to function in its natural ecological role.”
The let it burn strategy may have had impact on the Yellowstone fires, but as a 1998 article in Science argued, the problem may have been that they hadn’t implemented the policy soon enough.
Using network analysis to model the spread of forest fires, the researchers conclude, “the best way to prevent the largest forest fires is to allow the small and medium fires to burn.”
This is because forest fires follow a power law distribution: small fires are more frequent and large fires are rare. Most fires won’t reach 1988 magnitude and will burn themselves out before doing much damage. Allowing these fires to burn mitigates the risk of larger fires – because large fires are more likely in a dense forest.
This logic can be generalizable to other systems.
A 2008 paper by Adilson E. Motter argued that cascade failures can be mitigated by intentionally removing select nodes and edges after an initial failure.
Cascade failures are typically caused when “the removal of an even small fraction of highly loaded nodes (due to attack or failure)…trigger global cascades of overload failures.” The classic example is a 2003 blackout of the northeast which was triggered by one seemingly unimportant failure. But that one failure lead to other failures which lead to other failures, and soon a large swath of the U.S. had lost power.
Motter argues that such cascades can be mitigated by acting immediately after the initial failure – intentionally removing those nodes which put more of a strain on they system in order to protect those nodes that can handle greater loads.
This strategy is not entirely unlike the “let it burn” policy of the park service. Cutting off weak nodes protects the whole and mitigates the risk of larger, catastrophic events.