052 Forests, Wood and Carbon: A Living Carbon System

Walk through a forest and carbon probably isn't the first thing that comes to mind.

We see trees.

We see leaves, bark, branches and roots. We see birds, deer, squirrels, insects, mushrooms and countless other forms of life. We see fallen logs slowly returning to the soil. We may see valuable timber, future firewood, beautiful lumber or simply a wonderful place to walk.

But surrounding all of this is something we cannot see:

carbon.

Carbon is moving through the forest all the time — from the atmosphere into leaves, from leaves into wood, from roots into soil, from dead trees into organisms and eventually back into the atmosphere.

A forest is not simply a carbon warehouse.

It is a living carbon system.

It Starts With Photosynthesis

One of the most remarkable processes on Earth happens quietly in the leaves above us.

Trees take carbon dioxide (CO2) from the atmosphere and, using energy from sunlight, convert it into the materials they need to grow.

Oxygen is released in the process.

But the carbon doesn't disappear.

It becomes part of the tree.

Carbon becomes wood.

It becomes bark.

It becomes branches.

It becomes leaves.

It becomes roots.

A portion eventually enters the soil.

Year after year, a growing tree takes carbon that was once moving through the atmosphere as carbon dioxide and incorporates it into physical structure.

When we pick up a board in the woodshop, much of what we are holding was quite literally assembled by a tree using carbon from the atmosphere.

Carbon Storage and Carbon Sequestration Are Not Quite the Same Thing

These two terms are often used interchangeably, but there is an important distinction.

Carbon sequestration describes the process of removing carbon dioxide from the atmosphere and adding carbon to a reservoir.

Carbon storage describes the carbon that is already being held there.

Think about a large mature tree.

It may already contain an enormous amount of stored carbon.

A younger tree may contain much less carbon but may be adding new wood rapidly and therefore sequestering carbon relatively quickly.

That doesn't make one tree "good" and the other "bad."

They are doing different things within the carbon cycle.

The same principle applies to entire forests.

A mature forest may hold a tremendous carbon stock while a vigorously growing younger forest may be adding carbon at a different rate.

This is one reason forest carbon is much more complicated than simply asking how quickly trees grow.

Where Is the Carbon in a Forest?

When most of us imagine forest carbon, we probably picture the trunk of a large tree.

That certainly contains carbon, but it is only one part of the system.

Forest carbon accounting commonly considers five major pools:

1. Aboveground biomass — living trunks, branches, bark, foliage, understory vegetation and other living material above the soil.
2. Belowground biomass — the living roots beneath the forest.
3. Dead wood — standing dead trees, fallen logs and other larger dead woody material.
4. Forest-floor litter — leaves, needles, small twigs, decomposing plant material and organic layers covering the soil.
5. Soil organic carbon — carbon contained in organic material within the soil.

That last category is especially easy to overlook.

Some of the Forest's Greatest Carbon Storage Is Beneath Our Feet

We tend to judge a forest by what we can see.

A towering maple is impressive.

A massive oak is impressive.

A grove of mature hemlocks is impressive.

But beneath those trees is another enormous part of the forest carbon system.

The soil itself stores carbon.

Leaves fall.

Fine roots die and regrow.

Branches fall.

Fungi and microorganisms break organic material apart.

Earthworms, insects and other organisms move material through the soil.

Carbon gradually becomes incorporated into the forest floor and soil.

Some of it returns relatively quickly to the atmosphere through decomposition and respiration. Some can remain stored much longer.

This changes how we should think about forest stewardship.

Protecting trees is important.

Protecting forest soil is important too.

Good Logging Protects More Than the Trees Left Standing

This is another reason thoughtful harvesting practices matter.

When equipment travels through a forest, what happens beneath the tires or tracks deserves attention.

Severe rutting, erosion and unnecessary soil disturbance can damage roots, alter drainage and disturb the forest floor.

Good forestry and good logging therefore aren't simply about deciding which trees remain standing.

They are also about protecting the system those trees depend upon.

That includes water.

That includes regeneration.

That includes wildlife habitat.

And that includes soil.

Dead Trees Are Still Part of the Carbon System

A tree doesn't cease being part of the forest the moment it dies.

A standing dead tree can provide cavities and habitat for wildlife.

Eventually it may fall.

Fungi colonize it.

Insects use it.

Animals shelter beneath and within it.

As the wood decomposes, carbon moves through the forest system. Some returns to the atmosphere and some becomes incorporated into soils and other organisms.

This is why the idea that a well-managed forest should look "clean" can be misleading.

A forest isn't a lawn.

Dead wood can have tremendous ecological value.

Not every dead tree needs to be removed.

Not every fallen log needs to become firewood.

Carbon management is only one consideration within a much larger living ecosystem.

New York's Forests Are an Enormous Carbon Reservoir

New York is fortunate to have extensive forestland.

According to the New York State Department of Environmental Conservation, approximately 18.6 million acres of forest in the state hold roughly 2.9 billion metric tons of carbon.

That is an extraordinary amount of stored carbon.

But perhaps even more important than today's number is what happens to those forests tomorrow.

Will they remain forests?

Will they successfully regenerate?

Will invasive plants and insects change them?

Will young trees survive deer browsing?

Will forest soils remain healthy?

Will landowners be economically able to continue owning them?

The future carbon value of a forest depends upon the future of the forest itself.

Keeping Forests as Forests

This may be one of the most important forest-carbon strategies of all.

Keep forests as forests.

When forestland is converted permanently into another land use, we can lose both existing carbon storage and the ability of that land to continue removing carbon dioxide from the atmosphere through forest growth.

That brings us back to an idea we explored while looking at the future of wood markets.

Private forest ownership has costs.

There are property taxes.

Roads and trails may need maintenance.

Boundaries need attention.

Invasive species may need control.

Forest-management work can cost money.

And eventually one generation has to transfer that property to another.

A forest that can provide responsible periodic income may be easier for a family to keep intact than forestland that is simply an annual expense.

This creates a connection between economics and conservation that is sometimes overlooked.

A working forest can still be a conserved forest.

What Happens to the Carbon When We Harvest a Tree?

This is where the carbon story becomes particularly interesting for woodworkers.

Imagine a tree that has been growing for 100 years.

During those years it has taken carbon dioxide from the atmosphere and incorporated carbon into its wood.

Now imagine that good forest management calls for that tree to be harvested.

What happens to its carbon?

The answer depends heavily upon what happens to the wood.

If wood quickly decomposes or is burned, much of its stored carbon eventually returns to the atmosphere relatively quickly.

But suppose that log becomes lumber.

And suppose that lumber becomes a house.

The carbon hasn't suddenly vanished because the tree was harvested.

Much of it is now stored in the house.

A House Can Be a Carbon Reservoir

This gives us a wonderful new way to look at wooden buildings.

Walk into an old timber-frame house.

Look at the beams.

Look at the floors.

Look at the stairway.

Look at the doors and mouldings.

Those aren't merely architectural features.

They are stored carbon.

The tree may have been harvested 50, 100 or 200 years ago, but much of the carbon contained in that wood can remain there as long as the wood survives.

In effect, the craftsman or builder extended part of that tree's carbon-storage life.

The Woodworker Extends the Carbon Cycle

This idea has special meaning in woodworking.

Suppose we take a beautiful board and make a table.

The tree captured the carbon.

The sawmill turned the log into lumber.

The woodworker turned the lumber into something worth keeping.

If that table lasts 100 years, carbon remains stored in it.

If someone restores the table rather than discarding it, its useful life can become even longer.

If a piece of woodwork is treasured enough to pass from one generation to another, the carbon remains embodied in something useful and beautiful.

That gives craftsmanship an unexpected place in the carbon story.

Durability matters.

Build It Well — and Keep It

We often talk about craftsmanship in terms of beauty, strength and respect for the material.

Carbon adds another dimension.

A disposable wooden object has a short useful life.

A well-made wooden object can have a very long one.

A cheap piece of furniture might be discarded after several years.

A beautifully constructed hardwood table may survive several generations.

A timber-frame building may stand for centuries.

A door can be repaired.

A floor can be refinished.

A piece of furniture can be restored.

Wood has an extraordinary characteristic:

We can keep using it.

Restoration Becomes Part of the Carbon Story

This makes restoration especially interesting.

When we restore an old piece of furniture rather than replace it, we aren't simply preserving craftsmanship.

We are extending the useful life of the material.

The carbon that tree captured perhaps a century ago remains embodied in a useful object.

And we may avoid consuming some of the energy and materials required to manufacture its replacement.

The same principle applies to buildings.

Maintaining a wooden house, repairing old windows, restoring floors, preserving mouldings and reusing sound structural timbers can extend the useful life of wood far beyond the lifetime of the tree that originally produced it.

Suddenly the old saying:

"They don't build them like they used to."

takes on another meaning.

Building something to last can have environmental value too.

From Tree to House to Another House

We can carry this idea even further.

A timber doesn't necessarily reach the end of its useful life when the first building does.

Old beams can be salvaged.

Flooring can be reclaimed.

Barn boards can become furniture.

Structural lumber can sometimes be reused.

A tree might grow for 100 years, spend 150 years as part of a barn, and then spend another century as flooring, furniture or architectural woodwork.

The tree is gone, but its wood — and some of its stored carbon — continues.

Wood Can Also Replace More Carbon-Intensive Materials

There is another potential carbon benefit from using wood.

Producing materials such as steel and concrete can require substantial energy and create greenhouse-gas emissions.

In appropriate applications, wood can sometimes replace a portion of those materials.

This is one reason mass timber has attracted so much attention.

The carbon story isn't simply:

"How much carbon is inside the wood?"

We can also ask:

"What material did the wood allow us not to use?"

That requires careful life-cycle analysis because harvesting, drying, processing, transportation, adhesives, construction, maintenance and eventual disposal all have environmental effects.

Wood isn't automatically carbon-neutral merely because it came from a tree.

But responsibly sourced, efficiently processed, long-lived wood products can be an important part of a lower-carbon materials strategy.

This Changes How We Think About a Sawmill

A sawmill isn't simply cutting trees into boards.

In one sense, it is transferring carbon from one storage form into another.

forest carbon → log → lumber → building or product

The better the utilization of the log, the more opportunities we have to put that material into useful products.

High-grade lumber might become furniture or architectural millwork.

Structural lumber might become houses.

Lower grades might become pallets, engineered products or industrial lumber.

Chips and fiber can enter other products.

Sawdust and bark can have useful destinations.

As we explored in our discussion of future wood markets, perhaps one of the great opportunities for tomorrow's forest-products industry is simply learning how to create greater value from more of each harvested tree.

But Does This Mean We Should Cut More Trees?

No.

This is an important distinction.

The fact that wood products can store carbon is not an argument for indiscriminately harvesting forests.

Large living trees can hold enormous amounts of carbon. Forest soils store carbon. Dead wood has ecological and carbon value. Old forests provide important habitats and other ecological benefits.

Harvesting also changes forest carbon stocks in the short term.

The carbon question therefore cannot be reduced to:

"Cut the old trees and grow young trees because young trees grow faster."

Nor should it automatically become:

"Never harvest trees because standing forests store carbon."

Forests are much more complicated than either statement.

The appropriate management depends upon the forest, its condition, its history, its species, its soils, its wildlife, the owner's goals and many other factors.

Good forestry comes first.

The Forest Comes First

This brings us back to the principle from our discussion about future wood markets:

The existence of a market shouldn't determine whether a tree needs to be cut.

The forest should help determine that.

If good forest management calls for harvesting particular trees, then our job should be to find the highest and best use for the wood that comes out.

If a tree should remain because of its ecological, structural, habitat or other value, the existence of a buyer shouldn't change that decision.

Carbon becomes another factor in thoughtful forestry — not the only factor.

A Forest Managed Only for Carbon Could Miss the Forest

There is an interesting danger in focusing too much on any single measurement.

Suppose we managed every acre solely to maximize a carbon number.

What happens to wildlife habitat?

What happens to young forest species?

What happens to openings?

What happens to biodiversity?

What happens to forest resilience?

What happens when insects, disease, drought or storms arrive?

A forest isn't successful simply because we calculated the largest possible number of tons of carbon.

It is an ecosystem.

A healthy forest may contain huge old trees, middle-aged trees, saplings, seedlings, standing dead trees, fallen logs, openings and dense patches of young regeneration.

Different parts provide different habitat.

Different species perform different ecological roles.

Diversity can also make a forest more resilient when conditions change.

Carbon and Wildlife Can Share the Same Forest

This is where carbon connects naturally to wildlife management.

Some wildlife species depend upon mature forest.

Some require cavities found in older or dead trees.

Some need young forest.

Some thrive along edges and openings.

Others depend upon mast-producing trees such as oak, beech and hickory.

Healthy forests aren't all the same age and they aren't all the same species.

That diversity can benefit wildlife while also creating a resilient carbon system.

The objective shouldn't be to turn the forest into a carbon plantation.

It should be to maintain a functioning forest.

Forest Carbon Is Always Moving

It is tempting to imagine sequestration as a one-way process:

CO2 → tree

But nature doesn't work that way.

A better picture is a cycle:

atmosphere → tree → roots → soil → dead wood → organisms → atmosphere

And when people responsibly harvest wood, another pathway can branch from that cycle:

tree → log → lumber → house, furniture or other wood product → reuse or recycling → eventually back into the carbon cycle

Some pathways are short.

Some can last centuries.

A Wooden House Extends the Forest's Story

I particularly like thinking about an old wooden house this way.

Perhaps its floor began as trees growing in a forest 200 years ago.

Those trees captured atmospheric carbon long before automobiles, airplanes or modern power plants existed.

Someone harvested them.

Someone ran the logs through a sawmill.

Someone dried the boards.

A carpenter fitted them into a house.

Generation after generation walked across that floor.

Someone eventually sanded it and refinished it rather than tearing it out.

And there it remains.

The forest that produced those boards may have changed completely.

New trees may have grown where the original trees once stood.

Those new trees are capturing more carbon.

Meanwhile, some of the carbon captured by the earlier generation remains stored in the house.

The forest continued growing while the wood continued serving.

That is sustainable use at its most interesting.

What Does This Mean for the Woodworker?

Perhaps more than we initially realize.

Use wood thoughtfully.

Don't waste beautiful material unnecessarily.

Learn to use species that are locally available.

Design things that can be repaired.

Use joinery that can survive.

Restore good old woodwork when practical.

Salvage valuable wood.

Build furniture someone will want rather than something someone will throw away.

Build houses worth maintaining.

Make things that last.

The longer our wood products remain useful, the longer their story continues.

The Most Important Carbon Strategy May Still Be Keeping the Forest

After all the calculations, forest models and carbon accounting, we return to something remarkably simple.

We need forests.

We need young forests.

We need mature forests.

We need privately owned working forests.

We need protected forests.

We need healthy forest soils.

We need loggers who understand how to work responsibly in them.

We need foresters who understand how to manage them.

We need wood markets that give harvested trees valuable destinations.

And we need landowners who can afford to keep forestland as forestland for the next generation.

Carbon Credits: Another Possible Value From a Growing Forest

There is also an emerging economic dimension to forest carbon.

In some circumstances, forest owners can participate in carbon markets and receive income for management actions or commitments that increase or maintain qualifying carbon storage beyond an established baseline.

These programs can potentially give forestland another source of economic value without converting the land to another use.

But carbon credits are considerably more complicated than simply calculating how much carbon is contained in a forest and multiplying it by a market price.

Programs can involve inventories, baselines, verification, additionality requirements, long-term commitments, fees and restrictions or conditions affecting future management.

For some landowners they may provide an interesting opportunity.

For others they may not make economic or management sense.

Carbon markets deserve their own discussion.

But the concept raises an important possibility:

Could society increasingly recognize that a healthy, growing forest provides economic value simply by continuing to be a healthy, growing forest?

A Tree Can Have More Than One Carbon Life

Perhaps this is my favorite idea from this entire discussion.

A tree can spend a century growing in a forest.

During that time it captures carbon, provides shade, protects soil, moves water, produces seeds and provides habitat.

If good forestry eventually calls for its harvest, the best portion of that tree might become lumber.

The lumber might become a home that stands for another century or two.

Perhaps some of that wood will eventually be salvaged and used again.

Meanwhile, another tree can be growing in the opening left behind.

That younger tree begins capturing additional carbon.

One carbon story continues in wood.

Another begins in the forest.

The Forest Is Alive

We sometimes talk about carbon as though it were an accounting problem.

How many tons?

How many acres?

How many credits?

Those numbers are useful.

But they shouldn't cause us to forget what they represent.

A forest isn't a spreadsheet full of carbon.

It is sunlight falling on leaves.

It is water moving through soil.

It is fungi surrounding roots.

It is a seedling waiting for an opening in the canopy.

It is an old tree storing decades of growth.

It is a fallen log slowly becoming part of the forest floor.

It is wildlife habitat.

It is lumber waiting to become something useful.

And through all of it, carbon is moving.

A forest is not simply a carbon warehouse. It is a living carbon system.

Perhaps understanding that system changes the way we look at both forests and wood.

The standing tree matters.

The soil beneath it matters.

The wildlife around it matters.

The next generation of trees matters.

And when thoughtful forestry determines that a tree should be harvested, what we do with that wood matters too.

Forest → tree → wood → home → furniture → restoration → reuse.

Carbon can travel through all of them.

And if we manage the forest wisely and build with the wood wisely, that story can continue for generations.