What is an Old Growth Forest and why it matters
What Are Old-Growth Forests — and Why Do They Matter?
Old-growth forests are among the most complex, resilient, and valuable ecosystems on Earth. Found in pockets around the world — and especially in British Columbia — they are forests that have developed over centuries, sometimes millennia, without large-scale industrial disturbance.
They are not simply collections of old trees. Old-growth forests are living systems: deeply interconnected communities of trees, plants, fungi, animals, water, and soil that function together in ways younger forests cannot replicate.
What Makes a Forest “Old Growth”?
Old-growth forests are typically defined by their structural complexity, not just their age. They often include:
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Large, ancient trees alongside younger saplings
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Multiple layers of canopy rather than a single, uniform treetop layer
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Standing dead trees and fallen logs that recycle nutrients and retain moisture
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Rich communities of mosses, lichens, ferns, and fungi living on bark, branches, and forest floors
This layered structure allows sunlight to reach different levels of the forest, supporting a far greater diversity of life than younger, second-growth forests, which tend to have dense, closed canopies and far fewer ecological niches.
Because of this complexity, many plant and animal species — including birds, mammals, bats, insects, lichens, and fungi — can survive only in old-growth ecosystems.
A Forest That Functions as a Community
Forest ecologist Dr. Suzanne Simard has transformed how we understand old-growth forests. Her research shows that forests are not made up of isolated trees competing for resources, but are instead cooperative communities connected by underground fungal networks, often called the “wood wide web.”
In old-growth forests, the largest and oldest trees — sometimes called Mother Trees — act as central hubs in these networks. They share carbon, water, and nutrients with younger trees and seedlings, increasing their survival rates and helping regenerate healthy forests.
These underground networks also allow trees to communicate, sending chemical signals that warn neighboring trees of drought, pests, or disease. Over centuries, this web of relationships creates a forest that is remarkably resilient and adaptive.
Once an old-growth forest is logged, these networks are destroyed — and they can take hundreds of years to fully re-form, if they return at all.
Biodiversity That Cannot Be Replaced
Old-growth forests are biodiversity strongholds. In British Columbia, they provide habitat for species that struggle or fail to survive in managed forests, including:
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Northern spotted owls
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Southern mountain caribou
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Marbled murrelets
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Martens and fishers
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They also support thousands of lesser-known organisms — fungi, lichens, insects, and microorganisms — that play essential roles in soil health, nutrient cycling, and forest regeneration.
Ecologist Dr. Karen Price describes old-growth forests as ecosystems that have existed long enough for their many species to form an interdependent web — one that communicates, shares resources, and maintains balance across generations.
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Powerful Allies in the Climate Crisis
Old-growth forests are among the most effective natural tools we have for addressing climate change.
As massive carbon sinks, they store extraordinary amounts of carbon in their large trees and deep soils — often far more per hectare than younger forests. In BC’s coastal and interior temperate rainforests, old-growth ecosystems can store up to 1,000 tonnes of carbon per hectare, accumulated over thousands of years.
When old-growth forests are logged, much of this carbon is released back into the atmosphere, accelerating climate change. Protecting these forests keeps carbon safely stored while reducing emissions.
Because of their diversity and structure, old-growth forests are also more resilient to climate impacts such as drought, flooding, pests, and wildfire — helping protect nearby communities, watersheds, and wildlife.
Essential for Water, Land, and People
Old-growth forests play a critical role in regulating water systems. Their complex root networks and forest floors absorb rainfall, reduce flooding, stabilize soils, prevent erosion and landslides, and maintain clean, cool water for fish and human communities.
They also provide profound cultural, spiritual, and social value.
For many Indigenous Nations, old-growth forests are living relatives and teachers. Ancient western redcedar and yellow cedar have been used for thousands of years to build canoes, longhouses, and totem poles. As these trees disappear from many regions, Nations are increasingly forced to travel far from their territories to access remaining ancient cedar.
As Tahltan Nation forester Dr. Garry Merkel explains, old-growth forests are like Elders in a community — offering guidance, resilience, and lessons about how species live together in balance.
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How Much Old Growth Is Left?
Scientific assessments led by Dr. Rachel Holt, Dr. Karen Price, and colleagues reveal a stark reality:
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Only 3% of British Columbia consists of ecosystems capable of growing very large, ancient trees
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Within those areas, only 2.7% of forests remain old growth
Decades of industrial logging have dramatically reduced these ecosystems, leaving many of the most valuable forests unprotected and at immediate risk.
“Unfortunately,” Dr. Holt explains, “the most valuable old-growth forests are also the forests most valuable from a timber perspective. We have to decide whether we’re managing for short-term profit or long-term ecosystem health.”
Maps produced by independent scientists show that in many regions, remaining old-growth forests could be logged within the next 5–10 years without immediate intervention.
A Shift in How We Manage Forests
The Old Growth Strategic Review, led by independent experts including Dr. Merkel and Dr. Price, calls for a fundamental shift in BC’s forest management — moving away from prioritizing timber extraction and toward managing forests for ecosystem health.
Key recommendations include:
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Immediate protection for rare and at-risk old-growth ecosystems
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Temporary deferrals in areas facing imminent logging
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Publicly accessible maps showing the status of old-growth forests
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Strong collaboration with Indigenous Nations as leaders in stewardship
As David Suzuki has long argued, continuing to log old-growth forests reflects an outdated, extractive mindset that ignores the long-term costs to biodiversity, climate stability, water systems, and human wellbeing.
Why Protecting Old Growth Matters — Now
Old-growth forests are not renewable on human timescales. Once they are gone, they are gone for centuries.
They stabilize our climate, protect biodiversity, regulate water, support Indigenous cultures, and teach us how complex systems thrive through cooperation.
Protecting what remains is not just an environmental issue — it is a responsibility to future generations.