Canada is opening the floodgates on one of Earth’s greatest living reservoirs of CO2

Canada’s managed forest is one of the largest living reservoirs of carbon on the planet. For centuries it slowly filled, as billions of growing trees pulled CO2 from the air and stored it away in their wood. This ancient, continent-spanning, "carbon sink" helped keep the climate calm and cool. 

But in the last couple of decades, the flow of CO2 has completely reversed. Chainsaws and fossil fuel pollution are cranking open the floodgates that hold back this enormous reservoir of forest carbon. 

What started as a trickle a couple of decades ago has turned into a flood. Billions of tonnes of CO2 that were locked away in the forest have already drained back out on the backs of logging trucks and in the swirling smoke of ever more monstrous wildfires. This outpouring of forest carbon back into the atmosphere now dwarfs the fossil fuel emissions of most nations. And the crisis is accelerating.

That’s the sobering story told by Canada’s latest forest carbon data in its official National Inventory Report (NIR). 

In this article, I dig into government data to illustrate the immense scale and accelerating pace of this crisis, and some of the key ways humans drive it.  

Four billion tonnes of CO2, so far…

My first chart shows the big picture. 

That surging red line on the chart shows how much CO2 has been drained from Canada’s managed forest carbon reservoir and poured back into the atmosphere since 1990. 

The cumulative total reached 3,300 million tonnes of CO2 (MtCO2) by the end of 2022. That’s where the government data ends.

To provide a sense of scale, there are 150 nations that emitted less CO2 over those years from all their fossil fuel burning. I’ve indicated a few examples on the right side of the chart in gray text. For example, the combined fossil fuel emissions from all Central American nations since 1990 were half as much, at 1,700 MtCO2. 

Canada hasn't released its forest carbon data for 2023 yet. But, as you may remember, that was a record-breaking wildfire year. Turbocharged by global warming, the unprecedented fire conditions led to an explosion of wildfires that drained around one billion tonnes of CO2 out of forest storage and sent it billowing into the atmosphere in smoke. That super-sized burst of CO2 has likely pushed cumulative losses up to 4,000 MtCO2. I’ve indicated my estimate with a dotted line on the chart. 

An accelerating threat.

Sharp-eyed readers will have noticed that the red line on the chart continues to grow steeper over time. That’s the telltale sign that the outflow of CO2 is accelerating.

To show this more clearly, I’ve added stairsteps to the chart. Each one shows how many years it took to release another billion tonnes of CO2 from forest storage into the atmosphere.  

The first billion tonnes flowed out over nine years. The next billion took in six years. Then five years -- and most recently just two years. 

With CO2 pouring out so rapidly you might be wondering how much more CO2 there is that could follow. I sure did. Here’s what I found…

Tip of the iceberg.

The four billion tonnes of CO2 that’s already poured into the atmosphere is just the tip of the proverbial iceberg. If we are foolish enough to allow this crisis to continue, the remaining forest carbon on track to be released will wipe out any climate progress Canadians make elsewhere. And there’s more than enough to fill our summers with surging wildfires and choking smoke for centuries to come.

To calculate the remaining carbon, I turned to a Natural Resources Canada study that lists the "wood volume" in Canada’s forests at 50 billion cubic meters. That much wood stores around 60,000 MtCO2. A similar amount is held in roots and soil. This suggests at least 100,000 MtCO2 remains stored in our forest. 

This gigantic reservoir of forest carbon was a hugely valuable gift under our old stable climate. Back then, the forest was healthy enough to regrow more than we extracted. This provided jobs, energy, and materials that magically replenished themselves each year — literally out of thin air. As a bonus, when the reservoir refilled itself by pulling CO2 out of the air, it did a lot of the heavy lifting needed to keep our planet cool. 

In recent decades, humans have started to drain the forest carbon reservoir faster than it refills. That's transformed this wonderous gift into a dangerous threat. The two primary ways humans do this are by logging and fossil fuel burning. Let’s look at logging first.

Billions of tonnes of CO2 from harvested wood

To help illustrate the role of logging, I’ve created the graphic below. The red arrows show cumulative emissions of CO2 between 1990 and 2022. The green arrow shows the opposite -- the cumulative capture and storage of CO2 by new growth over those years (CO2 sink).

The red arrow on the left of the graphic shows the total CO2 transferred from forest storage into the atmosphere between 1990 and 2022. This is the same 3,300 MtCO2 we looked at in the first chart above.

Canada breaks these total emissions down into two parts: harvested wood and forest land. As shown in the graphic, total emissions (3,300 MtCO2) are the result of large emissions from harvested wood (4,600 MtCO2) that were only partially offset by a small CO2 sink from the forest lands (-1,300 MtCO2). The math: 4,600 - 1,300 = 3,300.   

That's a huge amount of CO2 from harvested wood. So, let's look more closely at what exactly is in this category. The category is officially called Harvested Wood Products (HWP). It covers all the wood physically hauled out of the forest. The carbon in these harvested wood products turns back into CO2 when the wood is burned for energy, or when it decays after being discarded. All wood products get burned or discarded eventually. Canada waits to report the CO2 on the books until the year the harvested wood product is burned or discarded. 

Annual emissions from harvested wood products have remained fairly steady at around 140 MtCO2 per year. This is one of Canada’s largest sources of CO2. It exceeds the annual CO2 emitted by all our nation’s passenger cars and trucks, plus all our homes. By the end of this year, 2025, the cumulative total from harvested wood will reach 5,000 MtCO2. That's five billion tonnes of industrially extracted carbon emissions since 1990. 

In addition, there are billions of tonnes more CO2 waiting in harvested wood products that are still being used.  

Billions of tonnes of CO2 in waiting

Harvested wood products still in use contain an additional 2,300 MtCO2 of "zombie CO2" that is waiting to be released. Canada has not reported this harvested wood CO2 on the books yet -- but they will when it is eventually burned or discarded. I've indicated the amount of zombie CO2 in waiting using a pale white arrow on the chart. 

Canada used to report harvested wood CO2 instantly in the year the trees were cut. Several years ago, they switched to the current method where they delay reporting the CO2 until the wood is burned or discarded. This new method requires tracking the fate of harvested wood, which they do using formulas based on the average useful life for each category of wood product.

The amount of carbon "stored" temporarily in harvested wood products is often portrayed as a good thing. But there are downsides. Most of that carbon was already being stored safely in living trees, and often for much longer. In addition, those living trees were actively pulling more CO2 out of the air, increasing the amount stored. Cutting trees reduces that forest carbon sink for decades or longer until new trees capture and store enough CO2 to catch up to what the cut trees would have added to storage. Aside from the CO2 impacts, hauling wood out of the forest hauls out important nutrients, structure, forest stability and habitat.

Logging also produces a lot of CO2 from the mess it leaves behind inside the forest.   

Billions of tonnes of CO2 from logged land

Logging activities disturb forest soils and leave massive piles of dead biomass behind ("slash"). I've updated my graphic to show the CO2 impact of this. To do this, I replaced the single forest land arrow with two arrows – one for logged areas and one for unlogged areas.

Forest areas that were logged at some point in the past are shown by the red arrow on the right of the graphic. These areas have collectively emitted 2,400 MtCO2 since 1990. This total includes the CO2 emitted by logging slash and disturbed soils. It also includes the CO2 removed from the atmosphere and stored away in new trees as they grow back after logging. It’s the net CO2 balance of everything on all lands that were logged at any point in the past.

We can now combine these two logging impacts -- harvested wood and logged landscapes – to see the total emitted since 1990 is roughly seven billion tonnes of CO2. 

Draining seven billion tonnes of CO2 out of forest storage and dumping it back into the atmosphere wouldn't pose such a big climate threat if Canada's managed forest was recapturing and storing away an equal amount of CO2. After all, that's the promise behind "carbon-neutral" wood – that the CO2 lost to logging is being balanced by CO2 recaptured by the forest. I’m guessing that most Canadians probably think this kind of CO2 balancing act is happening in our forest. 

Unfortunately, the government's data tells a different story. It shows that the rest of Canada’s managed forest – the unlogged areas – have only removed half that much. That's shown by the big green arrow on the graphic.  

As bad as those numbers are, the recent trends are decidedly worse. And, as we will see, these trends are being driven by fossil fuel burning.    

Collapse

The forest’s overall carbon sink has been collapsing for decades. It’s now completely gone according to the government's data. Instead of removing CO2 from the atmosphere, Canada’s managed forest is emitting CO2. And that’s piling up on top of the CO2 caused by logging. 

My next chart shows how this collapse unfolded. It breaks Canada’s forest carbon down by decade. 

Harvested wood has a brown bar in each decade. The CO2 emitted by this has remained business-as-usual high even as the forest sink has collapsed. 

Logged areas have a tan bar in each decade. The CO2 emitted by these have decreased but remains significant. (Note: this decrease seems to be the result of more logged area being left to mature, while harvesting targets the unlogged areas.)

The final part, the unlogged areas are primary forest that's never been cut. These have a green bar in each decade. This is where the carbon sink used to be. 

The big green bar on the left of the chart points down. This shows that three decades ago the unlogged areas recaptured two billion tonnes of CO2. That was close to the amount lost to logging back then. 

Now look at the middle decade. The green bar has shrunk in half. That shows that this carbon sink had collapsed in half. As a result, the unlogged areas only replaced half of the CO2 that logging drained out of the forest.

And in the most recent decade, this carbon sink collapsed past the tipping point – turning the unlogged areas into net emitters of CO2 instead. This is indicated by the small green bar on the right of the chart which is now pointing upwards. Logging a forest that didn’t grow back at all resulted in 1,950 MtCO2 of stored forest carbon pouring into the atmosphere during those years – an average of nearly 200 MtCO2 each year. 

What's driving the collapse of this formerly robust carbon sink? 

Surging wildfires and insect outbreaks

In recent years, wildfire and insect outbreaks have exploded in Canada’s managed forest. As the crisis intensified, Canada changed its forest carbon reporting method to separate out these impacts. My chart below shows the result.   

Canada divided the unlogged forest into three groups: 

1. Areas burned by wildfire in the last 60 to 100 years (red);
2. Areas killed by insects in the last 60 to 100 years (blue); and
3. Unlogged areas with mature trees (green). 

This lets you see that the big CO2 changes have been driven by recent wildfires and insect outbreaks. 

Three decades ago, these calamities were infrequent enough that regrowth won out over death. That can be seen by the red bar on the left of the chart. Notice that it points downward, indicating a net CO2 sink from recently burned areas.

Compare that to the tall red bar on the right of the chart. It points upwards, indicating massive emissions of CO2 from recently burned areas. This tells you that severe wildfires are now rampant -- killing the forest much faster than it can grow back.

The third group is the forest areas that escaped logging, wildfires and insect outbreaks during the last 60 to 100 years. These are shown with dark green bars. As you can see, the carbon sink in these mature unlogged areas has only declined a little. (Data detail: Two things are combining to cause this. The first is that harvesting is continually shrinking the number of unlogged hectares that remain. Second, the CO2 removed per hectare in unlogged areas has also been shrinking -- falling ten percent over these decades.) 

Before leaving this chart, I want to highlight the huge amount of CO2 that humans released from forest storage during the last decade. That’s the tall bar highlighted below.

This highlighted bar represents more than three billion tonnes of CO2 released during that decade.

Humans released around 1,800 MtCO2 of that through logging (brown and tan bars).

Humans released another 1,300 MtCO2 by priming the forest to burn more through a combination of land use changes and fossil-fueled climate changes. Wildfire isn’t new. But the dramatic increase (red bar) is new. And humans are responsible. 

Those same human actions have also increased the severity of insect outbreaks, which added another 300 MtCO2 to the pile.

Of all the ways humans are draining CO2 out of the forest, increasing the conditions for wildfire has driven the biggest change.

Wildfire is accelerating

To show how quickly wildfire emissions are growing, my next chart focuses on just the red and blue bars from the chart above. 

The first thing to note is that most of the CO2 surge from recently disturbed forest areas comes from the increase in wildfire (red bars). 

The second critical point is that these wildfire emissions have been accelerating. I highlight this non-linear trend with the curving red line. 

This acceleration of wildfire conditions is one of global warming's least understood threats.

As Jennifer Balch, lead author on a recent study of Western North American wildfires, explained to Bloomberg Green: “What we do know is that it takes just a little bit of warming to lead to a lot more burning”. Or, as another climate scientist, Park Williams, phrased it for The Atlantic, “each degree of warming causes way more fire than the previous degree of warming did. And that’s a really big deal.” 

To make safer decisions about our fossil fuel burning, Canadians need to know that continued global warming will bring far more extreme wildfire conditions to our forests, grasslands, and cities. 

Turning up the heat in Canadian forests

Forests in Canada are especially vulnerable to climate shifts because temperatures are rising here two to three times faster than the global average. That’s caused by a feature of Earth’s climate system called polar amplification. The farther north you are, the more rapidly the temperatures rise.

Extreme heat events are rising exponentially.

The fact that average temperatures are increasing by a few degrees might not seem very dangerous. But average temperatures don’t kill forests, extreme heat events do. And extreme heat events are increasing exponentially as the planet warms.  Climate scientist Dr. James Hansen has been warning about this for decades. Here’s one of his charts.

These bell curves show how summer temperatures have changed over the land areas of the Northern Hemisphere. Extreme heat events are shown by the dark red areas. For the math lovers out there, these are three standard deviations, or more, warmer than the 1951-1980 average. These extreme hot summer events almost never occurred back then -- but now they occur more than 20 per cent of the time. This exponential increase in extreme summer heat has brought a surge in extreme heat impacts, from flash droughts to megafire.

Too fast to adapt.

Natural Resources Canada was blunt about what's coming in their State of Canada's Forests 2020 report: "scientists predict that increasing temperatures and changes in weather patterns associated with climate change will drastically affect Canada’s forests in the near future. With the rate of projected climate change expected to be 10 to 100 times faster than the ability of forests to adapt naturally." 

Our trees don't get to move as we turn their climate 10 to 100 times more hostile. Instead, trees struggle, weaken, and grow less. 

Turbocharging insect outbreaks.

Struggling trees are far more vulnerable to insects, fungi, and disease. Native tree-killing insects, which thrive in warmer temperatures, now survive in larger numbers and breed faster as the climate has warmed. This unleashes population explosions that overwhelm forest areas in sheer numbers. Trees need lots of water to fight back by producing their primary line of defense: copious amounts of pitch used to block and engulf the invaders. Increased heat -- and the droughts that come with it -- have significantly weakened the ability of our trees to produce pitch, leaving them increasingly defenseless.  

Fueling megafires.

In addition, the surge in extreme heat events in our forest is unleashing another tree-killing outbreak -- monster fires. Studies show that just 3 per cent of wildfires in Canada are responsible for nearly all the area burned. These megafires erupt during excessively hot, dry, and windy days. Global warming has already loaded the climate dice to regularly roll out record hot-and-dry conditions outside anything our forests have experienced before. These record-breaking fire conditions produce recording-breaking megafires in size, speed and fury beyond anything experienced.

As NASA notes, extreme wildfire activity has more than doubled worldwide in recent decades – with the temperate conifer forests of Western North America and the northern boreal forests being hit particularly hard. Fire emissions in boreal forests have nearly tripled, "driven by a warmer, drier climate." 

A separate NASA report digs into Canada's record-smashing wildfires in 2023. Climate data shows that this was the warmest and driest fire season on record. By the time it was over five per cent of Canada's forest had burned (18 million hectares). As extreme as the temperatures were that year, NASA says this could become the norm three decades from now if global warming continues unchecked. The report ends with a warning: "if events like the 2023 Canadian forest fires become more typical, they could impact global climate." Destroying one of the planet’s great carbon sinks isn’t going to end well for anyone.

Another recent study found that climate change was driving a sharp increase in both wildfire emissions and intensity. Globally, wildfires now emit 50 per cent more CO2 per hectare. The biggest increases in both wildfire emissions and intensity are happening across the boreal forests of North America and Russia. These increases “pose a major challenge for global targets to tackle climate change, with fire reducing the capacity of forests to act as carbon sinks.” The conclusion states that “addressing the primary causes of climate change, particularly fossil fuel emissions, is central to minimizing future risks of forest fires globally and securing resilient forests for the future.”  

Fossil fuel emissions are priming the landscape to burn more. The threat from these rising wildfire conditions can be amplified by many of our land use changes. For example, logging often replaces fire-resilient older primary forests with more fire-prone young monoculture tree farms. The widespread cutting of trees and hauling them out of the landscape is an unnatural event for forests. And humans are heavily motivated by the value of what they extract -- which can create incentives to put a rosy spin on what they leave behind. The people that financially benefit from extracting trees say that the best way to reduce wildfire risk is more logging for "thinning" and "post-fire salvage". Others say this is an industry "smokescreen" to increase carbon extraction with little or no reduction in wildfire outcomes.     

Back to the big picture

I’m going to wrap up by returning to where we started: the big picture. Canada’s official forest carbon numbers tell us that our nation’s managed forest is in trouble -- and so are we. 

Billions of tonnes of CO2 that were locked away in the forest have already drained back into the atmosphere – intensifying global warming and ocean acidification. 

And this flood of CO2 is accelerating.

Humans are releasing this CO2 that was stored in the forest in two major ways – by logging and by burning fossil fuels which prime the landscape for increasing wildfire.

The time to stop an accelerating crisis is right now -- before the crisis can metastasize beyond our ability to contain it. What can we do?

Reduce logging CO2.

We’ve seen how logging is releasing billions of tonnes of CO2 beyond what the managed forest has taken back in. 

One option would be to give our forest more time to recover by cutting fewer trees -- especially in mature unlogged areas that remain its last large functioning carbon sink. 

Today, the number one use of harvested wood in Canada is burning it for energy. Doing this emits around 50 MtCO2 each year. For scale, that exceeds Canada's entire electricity sector emissions. And the global pressure to burn even more "forest biomass" is rising.  

Burning wood emits more CO2 per unit of energy than burning coal or other fossil fuels. The only situation where burning wood isn’t climate crazy is when the forest is growing back quickly enough to remove the equivalent amount of CO2.

But, as we've seen, that’s not happening with our managed forest. So maybe we need to stop extracting millions of tonnes of carbon from our faltering forest each year just to burn it for super-dirty energy.   

If Canada does allow more to be cut from its managed forest than grows back, we could at least treat the carbon extracted by the logging industry the same as we do the carbon extracted by the fossil fuel industry. The CO2 from both is piling up in the atmosphere and acting the same – overheating and destabilizing our climate. It's time we treated the carbon extracted from both of these industries equally, and put them under the same climate policies and climate targets. 

Stop feeding the wildfire beast.

We’ve also seen how the increase in wildfire is draining billions of tonnes of forest CO2 back into the atmosphere as well. This is tag-teaming with logging to wipe out the critical carbon sink in our managed forest. Climate science tells us burning fossil fuels significantly increases the wildfire threat. 

As the Intergovernmental Panel on Climate Change (IPCC) states clearly: "every tonne of CO₂ emissions adds to global warming." And because the wildfire threat has been accelerating with warming, every tonne of CO2 we emit in the future will spur on wildfire more than a tonne emitted in the past. 

So, we know what to do. If we don’t want to pass along a dystopian future to our kids and future generations of uncontrollable fire weather and summers filled with toxic smoke, then we need to stop feeding the beast with our fossil fuel burning — the gasoline we burn in our cars, the diesel we burn in our trucks and jetliners, the natural gas we burn in our buildings and industry, the coal we burn in our power plants. 

Fortunately, we have plenty of excellent clean and climate-safe alternatives to switch to.