California's old-growth sequoia trees are dying at an alarming rate - so land managers across the Sierras are mounting an emergency response. Many of the biggest, oldest trees on earth have fallen victim to mega-fires, bark beetle infestation and drought, all exacerbated by climate change. Jessica Morse, deputy secretary for forest and wildland resilience at the California Natural Resources Agency, said multi-tree die-offs are rare among sequoias - with only about 2 dozen lost between the ice age and 2015 - but now more than 10,000 old-growth trees have died since 2020. ...