The State of the Trees · Episode 4 of 13 · 20 min
The Beetle Summer: How Warming Unleashed the Bark Beetles
An insect the size of a rice grain has killed forests the size of states, because winter stopped doing its job. Milder winters no longer freeze overwintering brood, longer warm seasons let beetles finish a generation in a year, and drought-stressed trees cannot pitch out an attack with resin. The episode traces British Columbia's epidemic across some 18 million hectares and Colorado's outbreaks, and asks whether beetle-killed forests burn worse.
Where it happens
- British Columbia interior, CanadaEpicenter of the mountain pine beetle epidemic, about 18 million hectares
- Colorado+7 more episodesLodgepole pine and spruce beetle outbreaks
- California+30 more episodesWestern pine beetle in 2012-2016 drought die-off
Timeline
- 1999-2015British Columbia's mountain pine beetle outbreak runs its course
- 2008-2009Colorado's lodgepole outbreak peaks
- 2012-2016California drought and western pine beetle kill about 129 million trees
- 2022-2023Drought-linked fir engraver becomes the leading mortality agent in national surveys
Still debated
Whether beetle-killed forests actually burn worse is unsettled; a study of 81 fires challenged the intuitive story, and the evidence is mixed.
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