Ethiopian Review

The number of large-diameter trees in Yosemite National Park have declined 24-percent between the 1930s and 1990s.

The findings are based on a study done by the U.S. Geological Survey and the University of Washington. Scientists compared tree densities from 1932-1936 to those from 1988-1999 where large-diameter trees are those with a diameter greater than three feet.

Along with large-diameter tree loss, they also found a shift to fire-intolerant trees. Amazingly, this shift was experienced in areas that hadn’t seen a wildfire in nearly a century. Trees changed from fire-tolerant ponderosa pines to fire-intolerant white fir and incense cedar. In burned areas, however, the pines remained dominant.

Since large trees resist fire more than smaller ones, this loss could slow forest regeneration if an uncontrolled fire occurs. It could also lead to a decline in habitat. A reduction in species such as spotted owls, mosses, orchids and fishers is quite likely.

“We should be aware that more frequent and severe wildfires are possible in Yosemite because of the recent shift to fire-intolerant trees in unburned areas and warmer climates bring drier conditions,” said USGS scientist emeritus Jan van Wagtendonk.

But what’s the cause? Climate change is definitely a suspect.

“Although this study did not investigate the causes of decline, climate change is a likely contributor to these events and should be taken into consideration,” said Wagtendonk. “Warmer conditions increase the length of the summer dry season and decrease the snowpack that provides much of the water for the growing season. A longer summer dry season can also reduce tree growth and vigor, and can reduce trees’ ability to resist insects and pathogens.”

These conditions thwart heartier trees like ponderosas and sugar pines from taking root.

“Most of the water that becomes available in the Sierra Nevada comes from the snow pack,” said Jim Lutz, a researcher at the University of Washington who co-wrote the study. “Higher temperatures might increase populations of insects or make fungi more aggressive … which all could increasingly contribute to tree mortality.”

One fix might be a good old fashioned burning. Parts of Yosemite haven’t seen a wildfire for 100 years. This might have allowed other species to compete with the bigger trees.

“What we are really concerned with, is can all of the species that make up the ecosystem continue to persist with characteristic abundance,” Lutz said.

This decline could accelerate as the California climate becomes warmer the report warned.

My mom in 1963 drove through the tree with her dad and her dad’s cousin.

By Jerry James Stone | ecoworldly