The State of the Trees · Episode 10 of 13 · 24 min
Mexico to the Arctic: A Continent Rearranging
A south-to-north transect of roughly four thousand miles follows the trees of a continent that is rearranging under them. The route runs from the pine-oak highlands of Mexico and the Arizona sky islands through Southwest pinyon-juniper die-offs, the Great Plains eastern redcedar spread and Alaska's record spruce-beetle and fire years, to an Arctic treeline advancing far slower than warming would predict.
Where it happens
- Sierra Madre, MexicoWorld center of oak diversity, about 160 oak species
- Madrean sky islands, Arizona and New MexicoNorthern reach of Mexico's pine-oak woodlands
- Southwest pinyon-juniper woodlandsSite of the 2002-2003 pinyon die-off
- Great Plains+2 more episodesEastern redcedar spreading into grassland
- Kenai Peninsula, AlaskaSpruce-beetle outbreak across more than 1.2 million hectares
- Arctic treelineAdvancing north slower than models forecast
Timeline
- 1989-2004Kenai spruce-beetle outbreak kills spruce across south-central Alaska
- 2002-2003Brutally hot drought kills pinyon pine across the Southwest
- 2004Alaska's record fire season burns more than 6.6 million acres
- 2015Alaska's next-worst fire season burns about 5.1 million acres
- 2018-2021Utah juniper begins dying back in the Southwest megadrought
Still debated
Pinyon-juniper is both expanding and dying: it spread into grasslands across the 20th century but is now dying back in drought. Arctic treeline advance also remains well below early forecasts.