Ken Wu hunts down giant, old trees for a living.

As executive director of the Ancient Forest Alliance, he has hiked most of the watersheds on Vancouver Island and the Lower Mainland, hoping to find – and save from logging – the last remaining pockets of old growth.

At Echo Lake, just a 90-minute drive east of Vancouver near Harrison Hot Springs, local landowners brought him a few years ago to see a magical forest, draped in moss, with towering trees where up to 700 eagles come to nest when salmon are spawning in the nearby Harrison River.

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"Echo Lake is home to the largest night-roosting site for bald eagles on Earth," said Mr. Wu, who in 2012 launched a campaign to save the area, then slated for logging.

In 2013, the British Columbia government set aside 55 hectares, protecting just over half the old-growth cedars and Douglas firs around the lake.

Mr. Wu wasn't satisfied and since then has been pushing for the addition of another 40 to 60 hectares to the reserve, which would protect the key eagle area. "That would get the bowl, essentially the mountain and forest that rings Echo Lake. So it should be a no-brainer at this point," he said.

But last week, he was shocked when he walked through the forest around the lake to find that the biggest and oldest trees in the unprotected area had been tagged and numbered. A small company with cutting rights to a woodlot on Crown land at the lake has laid out the route for an access road, which it plans to build while awaiting logging authorization, Mr. Wu said.

"The government hasn't approved any cutting plans yet … so I think there's still some time here to fight this. My worry is that if the road-building progresses too far, they will have sunk enough cost into the whole thing that they are going to argue they have to recover those costs by logging the cut blocks. So right now, we are cranking up the pressure," said Mr. Wu, who is trying to raise public awareness about the threat to Echo Lake.

The Harrison area was logged in the early 1900s, but Mr. Wu said pockets of trees around Echo Lake weren't touched because they couldn't be easily reached. Others were passed up because they were considered too small at the time. Since then, they have grown into giants.

"Those cedars that are flagged now I suspect were about 50 years old [when the area was first logged] and 100 years later they are … essentially old-growth trees," he said.

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And they are rare.

"If you look at the entire region, and we've done it, we've explored this whole area, and it is exceedingly hard to find these types of lowland stands of ancient cedars. They are virtually non-existent – all logged, long ago," Mr. Wu said.

In an e-mail, Vivian Thomas, a spokeswoman for B.C.'s Ministry of Forests, Lands and Natural Resource Operations, said trees have been marked by the woodlot owner as an inventory, "with the goal of retaining as many of the large Douglas fir older trees as possible."

She also provided a fact sheet that states appropriate environmental measures are being taken around Echo Lake.

"Forest and resource values, including eagle habitat, are being adequately addressed by balancing established OGMAs [Old Growth Management Areas], a proposed wildlife management area and other reserve areas, with areas that remain available for timber harvesting," the ministry states. "The woodlot holder is aware of the eagle roosting habitat potential and has committed to further identify and manage the values within the woodlot area."

But Mr. Wu said it is clear when hiking through the forest that many giant, old cedars and firs will be lost if the government doesn't change course. And if those trees fall, the eagles and other wildlife will suffer, he said.

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"I would say logging these trees would have a detrimental effect because the eagles use the entire bowl. Essentially you see them come in from the Harrison River, they circle around the bowl and then they settle in the big trees along the side of the lake," he said.

"Even if they left some high-value eagle trees, essentially you get the loss of the ecosystem on the north and west side of the lake," Mr. Wu said. "When you go there, it is jam-packed with wildlife. There's a giant bear that hangs out there, … there are cougars in the area; you can see the trees that they've scratched. There's a little bobcat. … Ospreys are always over the lake. There's a group of otters … so it's not just an eagle issue, it's a biodiversity issue."

In his treks through the forests of the Lower Mainland, Mr. Wu has found only a few places with giant, old trees like those around Echo Lake.

And they are all in parks.