Part 1: Bark beetle just getting started on a continent-wide rampage

A tiny gem of a book -- "The Insatiable Bark Beetle" by Dr. Reese Halter -- tells the story of how unchecked global warming threatens to unleash our native bark beetles on a continent-wide killing spree through some of the oldest and largest forests on earth.

Humanity's unchecked emissions of billions of tonnes of fossil fuel pollution are overheating our forests. The ancient climate stability that has allowed long-lived trees and their complex forest ecosystems to thrive is being shattered. Our new ever-hotter climate is rapidly tipping the balance in favour of predatory tree-killing beetles.

New delicacies being served up range from the awe-inspiring 4,800 year old bristlecone pine trees perched atop California's remote desert peaks to the vast pan-Canadian northern boreal forests. From Arizona to Labrador, the future looks very tasty for forest destroying bark beetles.

For the billions of trees being exposed for the first time to the massive, synchronized, chemical warfare attacks of bark beetles, the future looks grim. If we want to save these magnificent forest ecosystems we will have to leave most of the known reserves of oil, natural gas and coal in the ground.

The short, pocket-sized "Insatiable Bark Beetle" packs a wallop. Dr. Halter spent months reading "a couple thousand scientific papers and several dozen books." Readers will be treated to a rare example of enjoyable general-audience nature writing that manages to weave in cutting-edge science from botany, biology, entomology, ecology and climate science.

But best of all it does what all good books do: it tells a compelling story on a grand stage full of rich characters. In this first article I'll cover the first part of the book where Dr. Halter describes the forest stage and the facinating beetles that are swarming across it.

The forests

Dr. Halter, a forest ecologist, sets the stage for this drama:

Earth contains seven naturally occurring biomes…the taiga and the temperate forest biomes provide the setting for the story that I aim to illuminate: the story of the insatiable bark beetle.

Taiga, also known in parts as the northern boreal forest, makes up the largest uninterrupted or contiguous, forested area on the surface of the Earth – the Earth’s emerald crown. ...the taiga contains one-third of all the trees in the world

And the dynamic tension:

All wild forests are teeming with life. They are biological treasure houses … the layers of interdependent life are bewitching.

An incredible balance exists between the characteristics of all components of a forest, from the tiniest insects, to the amount of sunlight, to the various tree species, to water – the lifeblood of the Earth.

His engaging writing goes on to describe the many ways our forests supply critical and widespread services to the global ecosystem and to us. He talks of how they build healthy rich soils; purify our water; control erosion; fill our air with oxygen while removing climate pollution; and build complex stable ecosystems that much of North America's wild plants and animals depend upon.

The tale brims with interesting details, such as: 

… the forest floor in the Carmanah Valley on Vancouver Island enables Sitka spruce, the tallest trees in Canada to reach over 95 meters. A square meter of the soil here can support 2,000 earthworms, 40,000 insects, 120,000 mites, 120,000,000 nematodes and many millions of protozoa and bacteria. They all “make a living” together … perpetuating the life of the forest."

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Nothing is comparable to the efficient filtration of fresh water that is completed by trillions of tree roots…Big trees can pump over 450 litres of moisture into the atmosphere every 24 hours.

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Pacific Northwest old-growth forests are superlative at capturing and storing vast amounts of CO2. Even after 200 years in existence, second-growth low-elevation forests could not compete with the magnificent storage capacity of the ancient forests … [while up north, the] boreal forests contain 47 per cent of the Earth’s stored carbon.

But all is not well. As the author is quick to point out: "in order to flourish and provide these and other benefits, forests have specific requirements and optimal conditions that need to be fulfilled."

It turns out that overheating the forests and unleashing hordes of voracious bark beetles isn't one of them.

The bark beetles

Enter, stage right, the insatiable bugs:

These destructive insects – each about the size of a plump grain of rice – number in the hundreds of billions and have killed billions of mature pine, spruce and Douglas-fir trees.

…bark beetles are devastating the forests like never before in modern times, perhaps in the entire history of conifers. Moreover, the beetles are advancing into regions of high-elevation forests, which typically rarely experience outbreaks. They are also venturing into the northern boreal forest, which has not evolved to defend itself…

The future of our forests in western North America is precarious.

How can such a tiny insect threaten the very existence of giant and ancient forests spanning thousands of kilometres? Dr. Halter goes on to weave the fascinating story of the bark beetles' sophisticated communication systems, biological tricks, chemical toolkits and evolutionary flexibility. These are no simple "bugs". They are formidable, well-armed and hyper-organized predators from which conifers have fled for their lives throughout their mutual history.

The targeted species of trees have survived only where they could effectively use their two main forms of defence against bark beetles:

1)    gobs of gooey resin that literally block the beetles

2)    the ability to survive extreme cold temperatures that kill the beetles

By warming the climate we are destroying both these tree defences across vast stretches of forests.

Rising temperatures are shifting the water cycle causing increasing summer droughts and water stress for trees. Thirsty trees can't make enough resin, or food, to fight off beetle attacks. Those rising temperatures are not just weakening the trees, they are also banishing the extreme cold that held back the beetles.

As Dr. Halter explains, if there is one thing cold-blooded insects thrive on, it is rising temperatures. Every aspect of the bark beetles lives is governed by temperature. Increasing the temperature is like turbo-charging the beetles.

Energized and unleashed into weakened and exposed new forest lands -- from piñon pines in Arizona to boreal jack pines in Alberta -- the bark beetle hordes are now on full attack. And what an attack it is!

I'll highlight just a few of the beetles' fascinating attacking tricks and tactics that the book reveals.

The bark beetles have a suite of specialized abilities that allows them to zero in on water-stressed trees. Water stressed trees can't make enough resin to defend themselves. The beetles can literally hear the ultrasonic noises given off as microscopic water columns in trees break when dried out. They can also detect infrared reflectance, plant surface temperatures, leaf yellowing and biochemical changes in distressed trees.

Bottom line: if a tree is temporarily weakened from a lack of water the beetles know it. And now global warming is increasing the number of trees suffering water stress. The table is set.

Once the victims are identified, the first scout beetles arrive. If the tree is suitable the beetles transform the tree's own defensive compounds into a chemical signal that:

...sparks a mass attack of thousands of mountain pine beetles, which usually lasts for about 48 hours.  Once the tree is completely colonized – 60 attacks per square meter of bark – mountain pine beetles halt the attack by using yet another bio-chemical cue as an anti-aggregate.

The strategy is to overwhelm the tree's resin defence system with sheer numbers. That would be bad enough. But the beetles bring along some nasty friends:

In order to defeat the tree’s autoimmune system, the beetle has evolved a mutualistic relationship with blue-stain fungi and bacteria. … After the beetle bores through the outer bark into the tree’s food supply, spores of blue-stain fungus, bacteria and micro-organisms are released from their mycangia, which are specialized pockets in the beetle’s mandibles.

Quickly germinating, the beetle’s partners effectively stop the tree’s production of resin. They then proliferate, impairing the water-conducting tissue, or xylem cells, in the sapwood. In part, the trees perish from an inability to draw water up to the crown in order to manufacture food in their leaves.

The full story Dr. Halter tells of the beetles amazing attack and coordination -- from bioacoustics to genetic flexibility -- makes for eye-opening reading. Several times I thanked my lucky stars I wasn't one of the billions of newly exposed trees in the beetles' path.

Once the beetles have eaten their fill and the tree has died, it is time to move on and attack another tree. Before they do, the beetles synchronously fill their mycangia with fungi, bacteria and other micro-organisms. Then off they fly in mass flights. Another wave of "biblical-style attacks" fans the deadly hordes outwards.

Our warming of the climate has opened huge new areas of forests to bark beetles. This gigantic new food supply has allowed the beetle populations to explode. Infestations have grown so massive that beetles are now overcoming "tens of millions of healthy, non-stressed trees."

Healthy old-growth trees that have survived for centuries -- and even millennia -- are now dying from this rapid fossil fuelled change to the landscape.

Up, up and away

In one of the books most memorable stories a glimpse of the future literally lands on the author's head:

In 2006 my faithful Chesapeake Bay retriever, Naio, and I were exploring the woods near Grande Prairie when the sky rained billions of beetles on us. It felt like we were being pelted by grains of rice. The shower continued for at least ten minutes. When I figured out that it wasn’t rice but beetles I was absolutely shocked.

…in 2002 and 2006, billions of mountain pine beetles were sucked into the upper atmosphere and spat out hundreds of km to the east, on the east side of the Rockies. Millions of the beetles that experienced this forced migration not only survived but successfully reproduced

What came next shocked the experts:

...Since 2006 the mountain pine beetles have noshed their way through Alberta’s lodgepole-jack pine hybrids in the northwest of the province and into the pure jack pine stands – an amazing adaptation by beetles advancing their way in a warming climate into a pine species that has never evolved to contend with such aggressive predation.

...now the brood adults are significantly smaller than the parent adults. Within one generation, the ravenous bark beetle populations have adapted to and are reproducing in trees with thinner phloem and smaller diameters.

The future of vast boreal is perilous if the warming continues:

Mountain pine beetles have successfully, for the first time in recorded history and likely ever, jumped into the jack pines of the Far North, beginning their march across the Canadian boreal forest to Labrador. In addition, there is a good chance they will infest the jack, red and eastern white pines of the lake states in the US northeast.

Sadly the threat is much larger than even that. Bark beetles are starting to rapidly expand their attacks on a large number of conifer species in forests throughout North America. This book's later chapters are dedicated to the natural history and unfolding beetle threats for several groups of conifers:

• Lodgepole  Pines
• Spruce Forests
• The Pinon Pines
• The Whitebark and Limber Pines
• The Bristlecone Pines

This article was part one of a two part series. The second part will give you taste of Dr. Halter's grand tour of each of these magnificent forest types and the troubled future that awaits them if we continue to overheat our planet.