Climate change, wildfires transforming biodiversity hotspot in Northern California

"As the climate continues to warm, big severe wildfires will be more frequent, and the dry conditions that follow will increasingly favor shrubs over conifers," researcher Jonathan Thompson said.
By Brooks Hays  |  April 30, 2018 at 11:59 AM
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April 30 (UPI) -- A region of forest in northern California and southwestern Oregon known as the Klamath is being transformed by droughts and frequent wildfires, new research confirms.

The region is historically well-adapted to wildfire, but rising temperatures and a changing climate are taking their toll on the ecosystem.

New analysis of the species found in the Klamath suggests the forest's iconic conifers are losing out to shrubs and other smaller plant species, which can rebound more quickly in the wake of a blaze. When fire-resistant shrubs and other species regenerate and take over the understory, it becomes more difficult for conifier species to grab a foothold.

"If the fire-free interval is too short or if the growing conditions are too dry, the shrubs can persist indefinitely, and the iconic conifers are squeezed out," Harvard ecologist Jonathan Thompson said in a news release.

For the last several years, Thompson and his colleagues have been surveying the regeneration of trees, shrubs and plants among the more than 500,000 acres charred by the region's record-breaking Biscuit Fire of 2002. Scientists used their findings to build a predictive model and simulate the impacts of climate change on the forest's regenerative abilities.

Their model showed that as global warming continues and the size, intensity, and frequency of wildfires increases, large conifers will increasingly succumb to the flames. Warming trends will also continue to depress the survival rate of new tree seedlings.

Scientists modeled the impacts of different warming trends -- from limited warming to moderate and severe -- on the health and makeup of the forest. They found shrubs and other understory species will continue to benefit at the expense of the regions iconic conifer trees.

While the shifts will be most pronounced under severe warming scenarios, scientists were surprised to find shrubs and other smaller species will continue to make inroads among the Klamath acreage whether warming trends continue or not. Even if current temperatures stabilize, a diversity of shrubs are likely to replace roughly a third of all trees by the end of the century.

Researchers believe decades of fire suppression in the region, disrupting the forest's natural burn and renovation cycles, has benefited the forest's largest trees at the expense of smaller species.

The ecologists published their findings on Monday in the journal Scientific Reports.

"As the climate continues to warm, big severe wildfires will be more frequent, and the dry conditions that follow will increasingly favor shrubs over conifers," Thompson said. "The combination will mean less of the conifer forest that make the Klamath so distinct."

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