Trees in old growth forests across the West are dying at a small, but increasing rate. Scientists conclude it's probably caused by longer and hotter summers from a changing climate.
The death rate isn't noticeable to someone walking through the forests. But according to a study published in the Friday edition of the journal Science, the rate' doubling every 17 to 29 years.
The study's lead author says if current trends continue, forests will become sparser over time.
He says there also could be cascading decline in forests that leads to less habitat for fish and wildlife, an increased risk of wildfires, and a vulnerability to sudden forest die-offs.
Beetle infestations are another culprit in the decline of forests in the western United States. Invasive species frequently attack trees already weakened by other environemental factor such a warmer climate.