'Empire of the Beetle': Reflections on the Kenai spruce bark beetle outbreak
When the spruce bark beetle outbreak hit Homer in the mid-1990s, I spent my weekends felling trees, cutting firewood and burning slash. My wife and I lived in a thick old-growth Sitka spruce forest, with no view of Kachemak Bay and hidden from the road. As the trees came down, our land became what realtors gleefully called an "emerging view" property. When a 160-acre clearcut appeared below us, our view of the Bay improved dramatically but cold day breezes meant the end of shorts on sunny summer days, and we found ourselves in full view from a noisy road. We loved our Sitka spruce and underlying thick moss, and it was heart wrenching to see it turned into a grass-filled stump farm.
Those troubled memories vividly resurfaced when I read Canadian journalist Andrew Nikiforuk's ""Empire of the Beetle": How Human Folly and a Tiny Bug are Killing North America's Great Forests" (Greystone Books, 2011). I couldn't have known it in the 1990s, but the Kenai outbreak was only the opening wave of a tsunami that has since swept British Columbia and most of the western United States, fueled by a rapidly warming climate. The mountain pine beetle (Dendroctonus ponderosae) has been the primary culprit further south, targeting lodgepole, ponderosa, and whitebark pines, with our spruce bark beetle (D. rufipennis) being a relatively minor player. Similarly, the pinyon engraver beetle (Ips confusus) has stripped the pinyon pine from pinyon-juniper forests in the Southwest.
As an ecologist at the Kenai National Wildlife Refuge in the 1990s, I had an insider's vantage point on the spruce bark beetle outbreak in Southcentral Alaska. As the Kenai forests turned red, I and my colleagues wondered if the magnitude of this outbreak was unprecedented. There had been a modest beetle kill in the 1970s on the northern peninsula, but it was peanuts compared to what was now happening. Using tree-ring methodology, we discovered growth releases in the 1810s, 1870s, 1910s, and 1970s throughout the peninsula and across Cook Inlet, indicating that beetles have long been major players in our forests.
The Kenai was the initial epicenter of the present North American outbreak, and Nikiforuk begins his odyssey with an account of "The Alaska Storm." He spent four years researching this book, which included an extensive review of more than a hundred years of bark beetle studies in the U.S., Canada and Scandinavia, as well as spending time in Canadian logging communities and traveling in the field with some of the top bark beetle experts.
"Empire of the Beetle" tells lots of interesting stories about bark beetle life, and the lives of the people who have studied them or been impacted by them. I found especially fascinating his description of the beetles as "buses" carrying fungi, mites, nematodes, yeasts and bacteria. Each beetle is a mini-ecosystem. Adult beetles, for example, carry fungi that release nitrogen from the wood, which larvae require because they can't live on the sugar-rich inner bark (phloem) alone.
The real message of this book, however, is the human response to the beetles. Ecologists have long noted that the human response to most natural disturbances is usually much worse than the disturbance itself. The bark beetle story is an extreme example of this proposition.
Lower-48 reporters often asked me about the ecological consequences of the Kenai outbreak. They expected stories of starving moose, massive forest fires and homeless songbirds. I told them instead that the most important consequences were logging, new roads and land subdivision. When the trees died, most private landowners on the Kenai logged their forests, seeking to salvage what little value remained. Logging usually required new roads, thereby improving the land for building (especially if the new view was attractive). Dense, roadless forests that wouldn't have been subdivided for decades were suddenly ready for subdivision and sales.
Reading Nikiforuk's book I feel that the Kenai got off very lightly compared to British Columbia in the logging aspect. In BC, most of the land is owned by the Crown. The BC Forest Service essentially gave loggers carte blanche to clearcut everything saleable, dead or alive, with few environmental restrictions. Some clearcuts exceeded 250,000 acres. Green pines were harvested in anticipation of beetle attack, and unaffected species like fir, balsam and spruce were also swept up in this frantic "gold rush" during the early 2000s. But the boom is winding down now and communities have lots of unemployed loggers, even as BC has spent more than a billion dollars repairing road damage caused by heavy logging trucks.
What lessons can be learned from all this? Except for a cold winter, Nikiforuk shows that a bark beetle outbreak cannot be stopped by logging, spraying, electrocution, burning, or explosives once it has gotten under way. Nevertheless, the public and politicians feel the need "to do something" about the problem, even if the cure is worse than the disease.
The second lesson is that unselective logging can intensify and prolong a beetle outbreak by leaving slash which breeds more beetles. Trees on clearcut perimeters typically are blown down and provide the best possible beetle nurseries. Slash and bucked up logs left along the Bradley Lake powerline in the late 1980s probably helped spread the outbreak at the head of Kachemak Bay.
The third lesson is that massive fires did not follow beetle kill in either Colorado or Alaska. Beetle-killed spruce does indeed burn, especially in the first-year red-needle stage, but drought-stressed live trees with dry needles burn even better. The rate of spread of most fires on the Kenai is determined by ground fuel moisture in litter or grass, and not by tree crowns, whether dead or alive. Dry weather, especially in the spring, is the chief fire danger.
The fourth lesson is that diverse forests are the best guarantee of healthy forests in the future. BC forests were mostly even-aged, post-fire stands that had been protected with years of fire suppression. The southern Kenai forests were also quite homogeneous with a long fire cycle of 400-600 years, historically protected by a cool and moist climate. In both cases these forests were loaded guns, waiting for a trigger to be pulled. The trigger was climate warming. In BC, prior to the 1980s, cold winters often reached the lethal temperature of minus 40 degrees Fahrenheit, which kills beetle larvae. Once winters warmed up, beetle populations exploded. On the Kenai, winters of that severity rarely occur and aren't a limiting factor; it was consecutive warm summers that pulled the trigger. An unprecedented 11-year run of warm summers from 1987 to 1997 allowed beetle populations to increase exponentially until they simply ate themselves out of house and home.
What should we do with logged land, if anything? I wish that Nikiforuk had addressed this conundrum. It is certainly on the minds of Kenai landowners. In my opinion, the best response is to do nothing. Planting white, Sitka or Lutz spruce is pointless because they will be susceptible to beetle kill with warming summers. Planted spruce could be harvested for pulp in 40-50 years, but I expect beetles will hammer these trees when their diameters reach 6-8 inches. Some landowners have successfully planted lodgepole pine, but it is only a matter of time before mountain pine beetles arrive from northern BC. Monoculture stands of lodgepole pine provide poor wildlife habitat and require fire to open their pitch-sealed (serotinus) cones for reproduction. Siberian larch also grows here, but it is susceptible to moose and hare browsing, and to larch sawfly, and it is expected to do poorly with warmer summers. Birch and aspen are nice in the yard, but they require fences or wire mesh to keep the moose off. From either an economic or ecological point of view, there appears to be no tree species worth planting on the Kenai on a large scale.
Cutover grasslands on the Kenai will eventually burn, as some have already done. If they burn late in the season, which we expect with warmer and drier summers, exposed mineral soil will provide a good seedbed for both spruce and hardwood germination. In beetle-killed forests that haven't been logged, the trees are falling down and rotting, becoming nurse wood for the next generation of trees.
The Canadian experience, as chronicled by Nikiforuk, makes a strong case that the best defense against massive insect outbreaks and large forest fires is to have a diverse landscape with a variety of stand ages and tree composition. The central and northern Kenai forests have this diversity because of the short fire cycle of 130 years in upland mixed white spruce and hardwoods, and 80 years in lowland black spruce. The southern Kenai could well achieve similar diversity because new forests will be recruited very unevenly if we wait for fire and nurse wood to do their natural work at their own pace.
In British Columbia there is great political pressure to reforest cutover Crown lands. Forestry is big business in BC, but it should be approached with great care and with an eye to the future. To simply replant monoculture crops of pine and spruce will create a mosaic of even-aged stands that serve as beetle fodder in a warming climate. A safer approach is to plant a variety of species, both softwoods and hardwood, on the same plots so as to mimic a natural forest. Forest pests like bark beetles, defoliators or blight can take out one tree species but not the whole stand. Foresters are developing poly-crop methods in the tropics and these methods certainly deserve study in our northern forests.
Ed Berg, PhD, was the ecologist at the Kenai National Wildlife Refuge from 1993-2010. He is now retired and lives with his wife Sara in Homer, where he is researching a book on the geology of the Kenai Peninsula, as well as teaching at the Kenai Peninsula College. This article is condensed from a longer version published in the Homer Tribune.