Old, Large Trees Important for the Climate

June, 2015

As climate disruption accelerates it becomes imperative that we all work together to cut emissions while removing carbon from the atmosphere, sequestering it long term. Yet we have only three options, and only one that truly works— our forests, nature’s greatest carbon storage bank.

The other forms of sequestration currently available are the oceans and geoengineering. Unfortunately, the oceans can no longer handle large amounts of carbon without becoming dangerously acidic, and geoengineering is both environmentally dangerous and prohibitively costly. For these reasons, our forests are our last hope. If left to grow, these same forests would provide habitat for endangered species, clean our water and provide unpolluted oxygen. It’s a no-brainer, yes?

Not if you ask the timber industry. They claim that clearcutting a forest every 40 years is a solution to global warming instead of a crime against humanity, a claim that shapes regulatory policy. An industry website explains the rationale this way: “When trees are harvested and manufactured into products, this carbon remains stored for the life of the wood product... One of the best ways to address climate change is to use more wood, as it is the most abundant, biodegradable and renewable material on our planet!”

This absurd concept is a bold-faced lie. Very little carbon from a forest ends up in a finished wood product. Most of a young tree’s carbon is found in the leaves, branches, stump, roots and soil, all of which is left behind, releasing much of its carbon shortly after harvest. Only about half of what makes it to the mill will become lumber while the rest is mill waste. Of that which does become lumber, roughly 90 percent will be in use for less than 40 years, and only one percent in use for 100 years—a time period that is still not to be considered long term sequestration.

The timber industry also claims a young forest takes in the lion’s share of carbon and not as much as it matures. This too is a lie. As a tree matures it adds ever greater amounts of carbon to its structure. The following quote from recent research highlights this fact; “Large, old trees do not act simply as senescent carbon reservoirs but actively fix large amounts of carbon compared to smaller trees; at the extreme a single big tree can add the same amount of carbon to the forest within a year as is contained in an entire mid-sized tree.”

This point has also been stressed by Andrea Tuttle, former head of CDF, who recently stated; “Forests are a huge carbon-storage bank, and represent our largest opportunity to remove carbon dioxide already in the atmosphere. When forests are lost to development, fire or degradation, they become a major source of emissions."

The key word is degradation. Forest degradation refers to the loss of biomass in forests through timber extraction—particularly clearcuts—and other activities which don’t result in conversion to other land uses. The IPCC has concluded that it would be impossible to solve climate disruption without addressing emissions from degradation, and the only way to address those emissions is by keeping our forests alive and not turned into perpetual carbon emitting tree plantations on short-term rotations.

The forests of western North America hold an important key to our survival in their ability to sequester carbon and store it far into the future. An old growth redwood tree alone can store roughly 2,000,000 pounds of atmospheric carbon and keep it locked up for over 2,000 years. On the other hand, a young redwood tree ready for short rotation harvest contains approximately 25,000 pounds of carbon. If that tree is cut down, over half of that carbon will enter the atmosphere in a short period of time and 90 percent of the rest over the next 40 years. At the same time, the regrowing forest is then ready for harvest and the cycle of cut and emit begins again, with the sequestration potential once again returned to zero.

We have a choice to make. We can continue with business as usual, and kiss this planet goodbye, or we can start looking for real solutions to climate disruption. If we do decide to save this planet it will mean a major shift in building practices, using alternative materials like stone or hay-bales for construction, or even log homes. There are millions of acres of cut over land in need of thinning where the smaller trees could be  used for log homes and the larger trees left to sequester ever more carbon.

But whatever we do it has to be done fast, as every day brings us closer to a climate disaster that the human race has never had to face, and is unprepared to cope with.