Human-forced climate change has already many effects that are
visible today. An article that appears in today’s Science
introduces another candidate: trees in the Western U.S. are
living only half as long as they did 50 years ago. In the
climate most of us grew up in, western forests acted as carbon
sinks. Their growth “scrubbed” carbon from the atmosphere.
Climate change has introduced conditions that are drier than
normal; severe drought has ensued across the region. As a
result, trees are growing less and dying earlier than they used
to. That could result in less carbon being removed from the
atmosphere, creating yet another positive feedback loop in the
climate system. Researchers focused on what’s called
“background” mortality – trees dying from events that do not
include infestations of insects like the mountain pine beetle
currently afflicting the West, which is identified as “abrupt”
mortality. They studied 76 plots where trees were at least 200
years old. They were undisturbed by logging (harder to d