As Alaska warms, birch tree tappers in Talkeetna wrestle with erratic season

A woman's hand holds a tap into a birch tree
SueEllen Bontrager aims a tap into a birch tree. She just drilled a hole into the tree to test if sap would come out. (Lex Treinen/Alaska Public Media)

The sun poked through the thick birch forest, warming the temperatures to a few degrees above freezing on a clear afternoon near Talkeetna. 

SueEllen Bontrager, who works at Kahiltna Birchworks, strapped on her snowshoes to go test the nearby trees to see if they were ready to harvest sap from. She tromped over deep crusty snow, stopped at a tall birch tree and drilled a tiny hole into its thick bark.

 She hammered in a small metal spout. But no sap dripped out. It was still too cold.

“Now it’s just a lot of waiting,” she said. “Because you can’t control the weather.”

The weather has felt more out of control in recent years, said Dulce Ben-East, one of the owners of Kahiltna Birchworks, the longest running birch syrup producer in the state.

As Alaska warms, she said, sap runs are getting earlier and less predictable. 

“I really think of it as climate chaos,” she said. “It seems to get more chaotic every year.”

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Dulce Ben-East (left) talks with employees including SueEllen Bontrager about testing trees for sap. Ben-East was hoping to tap trees today, but colder-than-expected temperatures mean the crew is testing trees and doing other maintenance on the property. (Lex Treinen/Alaska Public Media)

For the best sap production, the trees like temperatures that drop to just below freezing at night and rise above freezing quickly during the day. 

Ben-East has tracked data about the sap harvest since the business started in 1991. She has notebooks full of numbers. In the early years, she said, the first harvests started pretty consistently around mid-April. 

Then, beginning about 10 years ago, the data shows wild swings in the dates of first taps. East said she hasn’t analyzed all the data, but she thinks the sap season has gotten shorter too. National Weather Service climate researcher Brian Brettschneider said that’s not surprising. 

“It’s trending toward an earlier and a shorter window for those kinds of conditions which the sap producers say are ideal,” he said.

Precipitation levels have generally increased in Alaska over the past 50 years . That trend is expected to continue, according to the National Centers for Environmental Information. 

That can leave deep snow packs on the ground. Snow reflects sunlight and keeps air temperatures cold longer in the spring. But once snow melts, the darker soil warms up fast, making for a short, intense breakup. 

“The difference, especially when you have a high sun angle, is just really dramatic snow vs. no snow,” said Brettschneider, “And that’s a big factor in how the evolution of those above freezing temperatures develops into the spring.”

In other words: The sap season is shorter. 

Dulce Ben-East reads logs from early days of the birch syrup operation. She’s kept data from the last three decades years on snow depth, temperatures and sap harvests. (Lex Treinen/Alaska Public Media)

The changes in temperature also impacts sugar.

The process of turning sap into syrup relies on specialized machines to concentrate the sugars. 

When it starts running, sap is collected in 2,500-gallon tanks. Then it’s pumped through a reverse osmosis machine, which concentrates the sugars about 10 times. 

A diagram of the process of going from tree sap to syrup in Kahiltna Birchworks near Talkeetna. (Lex Treinen/Alaska Public Media)

Finally, it’s run through an evaporator which leaves just sweet sugars, turning what started as 100 gallons of sap into one gallon of syrup. 

Warmer temperatures mean less concentrated sap to start with, said Ben-East. 

“In a warm year, you really lose sugar fast,” she said. “Instead of having sap that’s 1.1% sugar, which is great, it’ll start dropping two .9% or .8% and at that point, it’s almost not worth making syrup from it. It just costs too much money.” 

Dulce Ben-East holds a refractometer, which can be used to measure sugar content of sap. “You want to see high sugar, some trees will give us 1.5%. This time of year average is about 1%,” she said. Warmer temperatures are leading to less sugary sap, she said. (Lex Treinen/Alaska Public Media)

There are other climate-induced changes that have Ben-East worried. Hotter summers mean greater chances of wildfires, which could wipe out the trees that the business relies on. A few years ago, the 2019 Deshka Landing fire was just a few miles from the company’s property. 

Ben-East has also noticed pests like aphids and leaf miners are more common. There’s nothing they can do to prevent them, she said. 

Plus, there’s the spruce bark beetles. Scientists believe that the bugs will be more prolific with milder winters. They struck a few years ago, killing scores of trees throughout Kahiltna Birchworks’ property. Then, winter winds brought the dead trees crashing down onto the network of tubing that brings the sap to a central collection site. 

Longtime employee Dylan Armstrong said he spent weeks cleaning up and fixing the damage.

“We’ve got to replace wire, we got to cut them out, we run the risk of cutting the tubing with the chainsaw,” he said. “It’s just tons more labor.”

Beetle-infested spruce trees falling on the sap collecting tubing has cost Kahiltna Birchworks weeks of labor. Scientists believe spruce beetle infestations could become more common as the climate changes. “It’s a total catastrophe,” Michael East, a co-owner of Kahiltna Birchworks said of the spruce beetles. (Lex Treinen/Alaska Public Media)

Later in the afternoon, after Bontrager went out in her snowshoes, temperatures finally warmed up to the mid-40s. Ben-East went to out to test more trees. And this time, sap ran a little more consistently. She hammered in another spout.

Clear drips started to form and drip into a white plastic bucket. 

“That’s what we want to see, the sap coming out as soon as you put the tap in,” she said with a smile. 

Ben-East said even with the challenges, adapting to the climate has always been part of the business.

It takes 100 gallons of sap to make one gallon of birch syrup. For maple trees, the ratio is close to 40:1 (Lex Treinen/Alaska Public Media)

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Lex Treinen covers culture, homelessness, politics and corrections for Alaska Public Media. Reach him at

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