Pine beetle infestation radically increases downstream runoff:

EDMONTON — Research indicates mountain pine beetles are likely to cause water problems for communities downstream of the forests they infest. I

EDMONTON — Research indicates mountain pine beetles are likely to cause water problems for communities downstream of the forests they infest.

Increased runoff from dead forests is likely to reduce the quality of the water in the streams and rivers that flow out of them, says Uldis Silins, a professor at the University of Alberta.

He suggests water treatment plants will have to be able to filter out more sediment and organic nutrients. As well, rivers downstream of the beetle-infected forests could also suffer algae blooms.

“When mountain pine beetles attack, it changes how much water the trees consume,” said Silins. “By killing these trees, the beetle is making a lot more water available.”

Silins said his research shows that, in a healthy forest, all water that falls during a growing season is either used by the pines or evaporates off their needles. In fact, those factors account for more than the total amount of rainfall and the trees depend partly on snow melt.

But all that changes in a forest killed by pine beetles.

“After they die, it means a good chunk of all that extra water is going to soak into the ground and start producing more runoff,” said Silins.

His study shows that water from a forest freshly killed by the beetles — when the pine needles have turned red but remain on the trees — increases by 40 per cent.

“That’s a lot of water.”

It ends up containing a lot of nutrients dissolved from the forest floor and soil.

“Those nutrients are a natural feature of our forest landscapes, but if we start flushing those nutrients out, that can cause the ecology of the rivers to change,” said Silins. “We’ll get more algae, more plants.

“That can also affect things like water treatment. If we have a lot more nutrients coming in to these municipalities downstream, that’s going to create challenges to treat the water.”

Silins points out that he is only partway through a three-year research project.

But what he’s already learned has important ramifications for forestry officials in beetle-ravaged jurisdictions from Colorado to British Columbia, he said.

“One of the big challenges for policymakers is going to be what kind of interventions should we be thinking about now to minimize those effects?”

There’s also a need to start thinking about how to get forests to grow back, he said.

“What can we be doing now to speed the redevelopment of the next forest, to shorten the period of time that we’ll have to deal with these water challenges?”

The Alberta government, which helped fund Silins’ research, is already considering the issue of beetle-resistant forests.

“We’re shifting to this area now — forest renewal,” said Duncan MacDonnell, spokesman for the province’s department of sustainable resource development. “That’s becoming a bigger priority.”

For example, forestry companies are being urged to cut the old stands of the trees the beetles prefer in an effort to change the age profile of the forest, he said.

Next week, the department expects to release its most recent survey of how many beetles survived the winter, said MacDonnell.

There’s plenty of knowledge about how forests respond to wildfires or clear-cutting, but scientists are just beginning to work out the long-term impacts of the mountain pine beetle, Silins said.

“This disturbance is unlike anything we’ve got information on.”