The environmental media is full of grim warnings about how much primary forest the world is losing and the impact this is having on biodiversity and our ability to reduce greenhouse gas emissions. But what exactly is “primary” forest, and how much does Canada have?

These are not easy questions to answer because people use different definitions and measure things differently. But let’s get one bit of confusion out of the way first. “Primary” forest is not the same thing as “old-growth” forest. Primary forest includes all ages of trees (young, middle-aged and old, all together) while “old-growth” is a specific, age-related criteria.

There is worldwide agreement, however, on four key aspects of primary forest: it is naturally generated forest (that is, not planted by man); comprises native tree species (not introduced species); there are no clearly visible indications of human activities; and ecological processes are not significantly disturbed[1].

The last two aspects require some clarification because the data to support them is sometimes tenuous or does not exist, or the extent of their impact is debateable or disputed. According to the definition used by the Food and Agriculture Organization of the United Nations (FAO), primary forest exists if there has been no known significant human intervention or “the last significant human intervention was long enough ago to have allowed the natural species composition and processes to have become re-established.” Human “managed” forests can fit in there (more on this in a minute).

Primary forest also includes forest where Indigenous peoples engage in traditional forest stewardship activities, but excludes forest where hunting, poaching, trapping, or gathering have caused significant native species loss or disturbance. The FAO definition also includes forest with visible signs of abiotic damage (storm, snow or drought) and biotic damage (insects, pests, and diseases). The area also needs to be large enough to maintain its natural ecological processes.

Using this definition, the FAO estimates that about one-third (34%) of the world’s forests can be considered primary. More than half of these forests (61%) are found in three countries (Brazil, Canada, and the Russian Federation)[2].

How do you measure it? 

So how much “primary” forest does Canada have? This would seem to be a simple enough question. But in reality, it’s a much harder one to answer. Because academic agreement on a definition is one thing. Being able to actually measure primary forest is something quite different. The FAO freely acknowledges the challenge when it says “the lack of an operational definition and consistent, easy-to-map indicators (means) some inconsistencies and bias are inherent” in what countries report. “Instead,” it says, “most countries use proxies based on land use and/or land cover to extrapolate data on primary forest, and these proxies vary.[3]”  

It’s not an easy problem, then. And while Canada does have a massive amount of data, fed into a National Forestry Inventory (NFI) dataset by provincial and territorial governments, it does not yet have any original data specifically on primary forest. What it does instead, when reporting in five-yearly intervals to the FAO, is rely on estimates based on extrapolations from multiple sources and methodologies, after using a combination of remote sensing from satellites, thousands of photo plots, and estimates by foresters on the ground.

You would think that the “easy” part of this highly complicated process would be to assess Canada’s unmanaged forest. This is a huge chunk of Canada’s total forest area (41%), according to a study commissioned by the Forest Products Association of Canada (FPAC)[4]. Much of it is remote and inaccessible and left in a wilderness state, disturbed only by fire, insects and beetles, winds, floods, and avalanches. And more recently by a rapidly warming climate. Clearly, most of this area fits the FAO definition of primary forest. It is also where most of Canada’s so-called “intact forest landscapes” (IFLs) are concentrated.

What is also “relatively easy” to measure is Canada’s legally protected forest areas. Human activities like harvesting, mining, and hydro-electric development are banned in nearly 95% of this. So, the remaining 5% has to be excluded from the primary forest count. As does the area around any roads that snake through our many national, provincial, and territorial parks.

The most difficult area to estimate for primary forest is what is called Canada’s managed forest (48% of the total, using the FPAC study). Managed forest does not mean harvested. This is forest land under a provincial or territorial government forest management plan using the science of forestry. But there’s a glitch here because the federal government uses a broader definition of managed forest. For carbon-reporting purposes, it includes both formal protected areas, plus hectares under fire suppression plans, and long-term forest management. Confusing!

Other complications

There are other complications. A recent study[5] indicated that over half of Canada’s managed forest contains conservation areas within it (for example, riparian and woodland caribou management zones) where harvesting does not occur or is deferred. How much of this meets the UN’s primary forest definition?

These are not easy questions to resolve. How can we be sure, in the absence of good historical records in the eighteenth and nineteenth centuries, for example, that an area that is now displaying every sign of being primary forest was not, in fact, logged many years, or decades, ago?

And now, time for the answer, or, at least, a best-guess estimate. Using proxy indicators such as forest land protection areas and proximity to human settlement and access (mainly through roads), the Natural Resources Canada team reporting Canada’s performance for the FAO’s latest (2020) report came up with a total: 205.1 million hectares[6]. That translates into 59% of Canada’s forest lands meeting the UN definition of primary forest in 2020, a pretty impressive number.

It also raises all sorts of other questions. There is an underlying assumption that primary forest necessarily provides greater benefits than other forests. Many forest scientists contest this assertion, arguing that eco-system-based management practices can emulate natural disturbance regimes and provide a mosaic of habitats with a natural range of variability. And in terms of carbon sequestration, research suggests that conservation is not always the optimal strategy[7], particularly where climate change is increasing wildfire risk[8].

Clearly, there is a need to improve the gathering of data on our forests. How best can Canada achieve its goal of conserving 30% of its lands and waters by 2030? (That 41% of Canada’s unmanaged forest would seem to be an inviting initial target). Will Canada ever stop harvesting trees from primary forests? Should it? And, how does Canada avoid trade barriers being placed on wood and pulp sourced from its primary forests by countries that themselves have already removed most of their own primary forests? Some big questions there!

[1] FAO, Global Forest Resources Assessment 2020: Terms and Definitions, 2020, (working paper 118) 2018, pp. 5-6,

[2] FAO and UNEP, The State of the World’s Forests 2020: Forests, Biodiversity and People, 2020, page 16  “According to FRA 2020 (Global Forest Resources Assessment 2020), approximately one-third (34 percent) of the world’s forests are primary forests (FAO, 2020). More than half of these (61 percent) are found in only three countries: Brazil, Canada, and the Russian Federation.”

[3] FAO and UNEP, The State of the World’s Forests 2020: Forests, Biodiversity and People, ibid.

[4] Forest Products Association of Canada (FPAC), Conservation Forestry – Careful Use of Canada’s Forest Resources. Unmanaged forest represents 41% of Canada’s forest lands; legally protected forest 11%; and managed forest 48%. For a summary see John Mullinder Who’s “Spinning” Who? Some Facts on Canada’s Forests, Logging, and the Caribou,

[5] Belanger, E, Roddy, D, and D. Baldwin, 2020. Calculating the extent of conservation lands within Canada’s managed forests, Forest Products Association of Canada.

[6] FAO of the UN, Global Forest Resources Assessment 2020: Country Reports 2020 (Canada)

[7] Sharma T, Kurz WA, Stinson G, Pellatt MG, Li Q. 2013. A 100-year conservation experiment: impacts on forest carbon stocks and fluxes. Forest Ecology and Management 310:242-255. and Smyth CE, Stinson G, Neilson ET, Lempriere TC, Hafer M, Rampley GJ, Kurz WA, 2014. Quantifying the biophysical mitigation potential of Canada’s forest sector. Biogeosciences 11: 3515-3529.

[8] Wotton BM, Flannigan MD, Marshall GA 2017. Potential climate change impacts on fire intensity and key wildfire thresholds in Canada. Environmental Research Letters 12, 095003.