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Scientists track how blueberries behave in climate change

By ERIC BARKER, The Lewiston Tribune

LEWISTON, Idaho (AP) — Blueberries are highly sought after, but the coveted mountain fruit was hard to come by in much of northern Idaho and eastern Washington this year.

Pickers were able to locate some productive plants and plots, but they frequently encountered healthy bushes that had few or no berries, the Lewiston Tribune reported on Friday.

“In general terms, it’s not been a very good year,” said Wayne Kasworm, a grizzly bear biologist for the US Fish and Wildlife Service who tracks blueberry production in the Selkirk, Cabinet and Yaak mountain ranges.

With a changing climate, scientists like him are increasingly tracking blueberries which are an important food source for grizzly bears and other wildlife and are also coveted by people. Native Americans have been harvesting blueberries for thousands of years and continue to do so today. Small berries with a pleasant mix of sweet and tart are also targeted by recreational and commercial pickers. They are used to make pies, ice cream and other desserts, added to pancakes, milkshakes and smoothies.

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Grizzly bears rely on berries as their primary food source.

“I started looking at blueberries in part because they’re such a big part of the bears’ diet,” said US Geological Survey scientist Tabitah Graves. “Glacier National Park, where most of my work is focused, blueberries make up over 50% of their diet at the height of summer, so that’s a pretty big component and during the time they’re getting bigger to be able to hibernate. ”

During the study of plants, she learned how important they are to Native Americans and other peoples, and how they play a small role in rural economies. Small restaurants and stores sell blueberry products, and some people make extra money by picking and selling them.

But it’s not just people and bears looking for the berries.

“The other thing I learned during this work is how many other species depend on blueberries. It really is a keystone species,” Graves said. “We found coyote, marten and weasel droppings (with berries) and recorded pictures of all kinds of birds and small mammals also eating blueberries. I don’t know how important they are to all these species, but I do know that they are part of their diet.

Graves studies what blueberry plants need at different stages of their development to produce berries and how plant distribution might change in response to climatic factors such as larger and more frequent high-intensity wildfires.

She and a graduate student have identified five species of bumblebees and other bees that help pollinate plants. One of them, the western bumblebee, is in decline and a candidate for protection under the Endangered Species Act.

“Occupancy was down 93% from 1998 to 2018, which is all across the western United States. It wasn’t as bad here in the Northwest, which is fine, but it’s concerning,” Graves said.

Researchers like her want to know how new fire regimes may affect the plant. Blueberries need lots of sun and tend to like the kinds of openings that fires often create. When the forest canopies close due to vegetation succession, the bays are often shaded.

Some Native American tribes used fire to manage bilberry habitat. But these burns tended to be of low intensity. Many fires today, driven in part by climate change and a buildup of biomass from past fire suppression, are burning much more intensely.

“Historically, fire was intentionally used to regenerate shrub fields and make them produce more blueberries, but now we’re under a different system and a different climate,” Graves said. “We don’t really know yet what more severe fires – what kind of impacts that will have on (berry) distribution.”

Graves developed a method to track the distribution of blueberry plants using aerial photography to capture the plant’s seasonal color change. They turn red in late summer and fall. She and her team used color to map blueberry habitat, then conducted site visits to determine the accuracy of the method.

Janet Prevey, another USGS scientist, studied how the plant may respond to climate change. It could be dramatic. Plants may become less prevalent at some lower elevations and drier sites. This could mean blueberries are retreating from part of the plant’s southern range and advancing into northern latitudes.

Prevey found that blueberry habitat, under certain carbon emission scenarios, could be reduced by 5-40% in the northwest and could expand by 5-60% in northern British Columbia, Canada. Likewise, the timing of flowering and fruiting could change. She found that flowering could move forward 23-50 days on the calendar and fruiting could move forward 24-52 days.

“Where there are lots of blueberries now, we may see less blueberry growth in the future,” she said. “But all of this is based on climate modeling and projections.”

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