Many British Columbia residents have already made the connection between global warming and the onslaught of mountain pine beetles across the province. It has often been reported that these pesky bugs keep surviving warm winters, enabling them to munch their way across a huge swath of B.C. forests. But few of us are aware of the potential links between the mountain pine beetle and large floods in the Fraser River watershed.

At last November's annual meeting of the Fraser Basin Council, Allan Chapman provided some insights into what could happen. Chapman, head of the B.C. Ministry of Environment's River Forecast Centre, cannot be accused of being an ill-informed fearmonger. With training in forest hydrology—the study of stream flows from the forests—he is well-equipped to discuss the impact of dead pine trees on the spring runoff of melting snow.

Chapman said that B.C. is experiencing the most extensive beetle outbreak ever recorded in North America's 500-year colonial history.

In his 20-minute presentation, entitled “Mountain Pine Beetle in the Fraser Basin—Implications for Floods”, he noted that the beetles spread from five separate epicentres, aided by global warming in the 1990s.

Provincial and federal government scientists, he said, are predicting that if abnormal weather trends continue, more than 80 percent of all of B.C.'s pine forests will be dead by the end of 2013.

Pine trees make up about a third of all B.C. forests species. Already, more than 10 million hectares of Interior forest lands—just over 10 percent of B.C.'s land base—have already been infected to varying degrees of mortality, he said.

The beetles previously only attacked older pine trees. But field reports from staff working for the Forests and Environment ministries now say that the bug is zeroing in on seedlings in young plantations.

So what does all this have to do with flooding in the Fraser River watershed, which extends from the City of Richmond all the way to the Rocky Mountains? Chapman said that most of the forests in this region—60 percent, or 13 million hectares—extend from valley bottoms up the sides of mountains. Of those, more than 50 percent are pine forests.

This means that there are seven million hectares of pine forests in the Fraser River watershed—pine forests that are currently being destroyed, have been destroyed, or possibly will be destroyed by the mountain pine beetle.

As any forest hydrologist will tell you, forests slow down the rate of melting snow. The trees partially or completely block the sun, providing shade that delays the melt. In addition, living trees' roots absorb water, which also regulates the runoff.

Chapman pointed out to his audience that the death of so many pine trees will change the forest hydrology in large parts of the Fraser River watershed. Dead forests will not be able to slow down the rate of melting snow as intact forests have traditionally done. This could result in a rapid rise in water levels in the Fraser River from its many affected tributaries. And that, he predicted, will eventually cause widespread flooding.

Chapman wasn't the only speaker at the conference. Monica Mannerstrom, senior project engineer with Northwest Hydraulics Consultants Ltd., gave an overview of the Lower Fraser River's intermunicipal dyking structures from Agassiz to Richmond. She showed old photographs of the last great Fraser River flood in 1948, which inundated homes, businesses, and farms.

Mannerstrom also linked the mountain pine beetles to possible flooding.

“Certainly we need to inform all levels of government that there is a problem, so that nobody can say that they didn't know,” she said.

B.C.'s climate and rainfall patterns are changing from global warming. What was once predictable, such as a dry Interior winter or spring, may no longer be so reliable for predicting spring runoffs. In many western portions of B.C.'s pine-belt Interior, snowfall accumulations are at record highs, elevating flood risks for this spring.

Of course, global warming isn't the only reason for increasing numbers of beetles. Forest-management practices over the past 80 years have been contributing factors. Silviculture methods emphasizing single species and the suppression of natural fires have changed the genetic makeup of the land base. Many forests have also been made vulnerable by the careless dispersal of beetles falling off logs being transported by truck or rail.

But why haven't the federal and provincial governments publicly drawn connections between rapid logging of beetle-infested forests and the likelihood of future floods on the Fraser River? Certainly this information has been available to those interested enough to look for it.

According to a 2004 Alaska state research bibliography report, entomologist Ed Holsten stated that similar beetle epidemics in the United States caused “large increases in stream flow” that endured “25 years after this outbreak”. Holsten's summary was not mentioned in a similar November 2005 federal research report on historical beetle surveys and resultant increases in water flows.

Forest hydrologists study ways in which forests control stream, river, and groundwater sources. But prior to 2005, federal and provincial administrators largely ignored the issue of hydrology in developing strategic logging plans to address the beetle epidemic in B.C.'s watersheds.

In August 2004, Ministry of Forests science researcher Marvin Eng cautioned B.C.'s then–chief forester, Larry Pedersen, about hydrology.

This came in a small paragraph in a ministry document called Technical Report Number 019. Eng wrote that Pedersen's consideration of increasing the rate of Interior logging to “salvage” beetle-infested timber would “adversely” affect water runoff because many areas had already been previously logged.

Pedersen appeared to have ignored Eng's advice, authorizing large increases to annual logging rates in three midnorthern forest regions by October 2004.

Pedersen's replacement as chief forester, Jim Snetsinger, wrote an eight-page “guidance” report in December 2005. It defended Pedersen's controversial decision, although Snetsinger acknowledged that the “80 percent” increase in logging would pose “a significant risk of hydrological problems”. Snetsinger noted that he was “mindful” of the issue.

Instead of a precautionary approach, logging politics had won.

Concerns over hydrology only began to take prominence a year and a half ago. In a July 2005 Forest Ministry report called Beetle Stewardship Research Strategy, this issue was given the “highest priority” rating alongside silviculture research. However, the report noted that numerous hydrological impacts from beetles and logging—such as rising water tables, landslides, road failures, stream channel erosion, increased sediment in water courses, fish-habitat destruction, warming waters, and floods—were all identified as having considerable “knowledge gaps”.

In late August 2006, I took a trip north into B.C.'s Interior, where I observed horizon after horizon of endless red and grey stands of dead pine forests. Afterwards, I spent six weeks contacting university professors and government staff and gathered numerous reports. To my surprise, I discovered that the majority of B.C.'s pine forests are concentrated in the Fraser River watershed.

That raised a big question: were there legitimate concerns about potential flooding in the Lower Fraser River, which is home to a large human population and plays a central role in the provincial economy?

To find the answer, it was necessary to analyze statistics on the amount of previous logging, as well as on areas burned by fires. But I was told that the provincial government had never conducted such a study. One alternative was to use Google Earth to look at visual satellite imagery of the logging. This was a formidable task, given the area was the size of Great Britain.

The second necessary piece of information was estimating the area of pine forests in the watershed killed by beetles. The government's statistics are inconsistent, and not all figures are available.

Chapman's estimate of close to seven million hectares of pine forests in the Fraser River watershed seemed reasonable.

Overlapping information about logging and beetle infestations helps determine the percentage of the land base that has been disturbed. This is a method commonly used by forest hydrologists.

Some fascinating new information emerged at last October's annual conference of the B.C. chapter of the Canadian Water Resources Association. Steve Chatwin, a senior forest hydrologist with the B.C. Forest Practices Board, highlighted unpublished findings from the first forest-hydrology study conducted on beetle-infested timber, at Baker Creek. That's a heavily logged watershed just west of Quesnel.

Chatwin relied on computer modelling. He demonstrated that if dead pine trees were left alone and not logged, this would lessen the severity of the spring runoff by half. This is called “peak runoff”. The shade from the standing trees would slow the rate of melting snow.

Chatwin's conclusions conforms with first-year tested field results from four recent studies on snow-melt characteristics in beetle-killed forests. They were conducted by Prince George hydrology consultant Pierre Beaudry, Williams Lake–based Ministry of Forests hydrologist Paul Teti, Kamloops-based Ministry of Forests hydrologist Rita Winkler, and University of Northern B.C. assistant professor of geography Sarah Boon.

Here's what the public might conclude from all of this. If all the pine forests in B.C.'s Interior had never been logged—and given their conversion from living to dead forests—good forest-hydrology science would recommend against conventional logging operations for decades within a majority of those stands. That would delay the spring runoff, alleviating the risk of flooding in the Fraser River and its tributaries, as well as other rivers.

Already, there is an elevated risk of runoff from industrial clearcut logging, not to mention from the maze of logging roads. For the past 60 years of B.C. history, increases in logging have been associated with fish-habitat destruction, landslides, erosion, flooding, drying of streambeds, and the ruination of drinking-water sources.

There is a close bond between trees and water flows. If the government gives the green light to logging all the beetle-infested forests in the B.C. Interior, it could bring in billions of dollars for forest companies. It could also generate tax revenue for the government. No wonder that the hydrology issue has been sidelined.

In the early 1970s, Idaho-based hydrologist Al Isaacson introduced a phrase called “equivalent clearcut area”, or ECA. It's a hydrological threshold used to provide recommendations when cutting can resume in already logged areas. Here in B.C., forest hydrologists calculate the amount of logging or disturbance that can occur in a given watershed before it begins to seriously affect water runoff and increase erosion.

For instance, a large stand of dead pine trees dominating a watershed has an ECA of about 50 percent. This is well beyond the 35-percent maximum threshold that B.C. hydrologists now allow. But that didn't stop Pedersen and Snetsinger when they approved increased logging rates in beetle-infested forests, ostensibly to make use of the timber.

An unprecedented 40-year study in forest hydrology in Oregon illustrates the seriousness of the “hydrologic” recovery rate. U.S. Forest Service hydrologist Gordon Grant's 1995 report found that full hydrologic recovery only occurs 40 years after logging. The figure extends to 50 years or more in B.C. because its more northern forests grow at a slower rate than those in Oregon.

If Grant's findings were applied to B.C., it would take until 2060 or longer before water flows began to assume their normal patterns in a reforested Fraser River watershed landscape.

The Fraser Basin Council's 2006 State of the Fraser Basin Report conservatively estimates that “potential flood damages” here “range from $2-$6 billion, not including the indirect costs associated with the disruption of critical infrastructure and the economy”. That's a big price to pay.

The council's report does not link flood risks with forest mismanagement. But whatever the costs of flooding turn out to be, don't be surprised if a tide of resentment rises against those who decided to gamble with the Fraser River watershed in the pursuit of short-term profits.

Will Koop is coordinator of the BC Tap Water Alliance, a citizens' group that advocates for the preservation of community watersheds.