Marcus Zwicker: Managed forests sequester more carbon than unmanaged forests

Some do, some don’t; the statement is unlikely to apply to current management of the forests of Nova Scotia

In a post on Marcus Zwicker’s Facebook page, the WestFor General Manager presented the diagram below, with the comment “Managed forests sequester more carbon than unmanaged forests, here’s how……”

The post seems to have been popular, with 45 shares and laudatory comments including one by RM, a senior L&F bureaucrat, and a request to share widely by RB, an advocate of producing biofuels from NS forests .

I could see the page, but not comment (that’s apparently limited to Facebook friends of MZ) so… I will offer my perspective here.

Whether or not the statement “Managed forests sequester more carbon than unmanaged forests” is true or not depends on the geographic location and history of the site and the landscape in which it is embedded. I think no credible climate modeller would suggest the diagram accurately depicts all forests; it may be true for some, not for others, with many in-between, depending on recent conditions (e.g. the fires in Western Canada in the last few years), management etc.

The diagram suggests a fire return interval in unmanaged forests of approximately 150-200 years, with all carbon in the unmanaged forest apparently returned to the atmosphere at the end of the cycle. That simply does NOT apply to the Acadian forest and Nova Scotia, except perhaps for a couple of centuries following the initial arrival of Europeans. In the latter 20th century and in pre-European times, the fire return interval is well over 1000 years (see, e.g., Wein and Moore, 1978; and a popular article by Donna Crossland)

To address the issue of how forest management affects carbon storage for Nova Scotia, what needs to be documented/modelled are the stocks of carbon in forest soil and vegetation,  how those stocks have been changing over last 50 or so years, and how they will change in the next 12- 50 years under current management practices, under a range of alternative management practices, a range of uses of harvested products, and under a range of climate scenarios.

I say 12 to 50 years because of the IPCC warning that “We have 12 years to limit climate change catastrophe“. What happens over the next 10-20 years is very important.

Presumably, this sort of modelling/accounting is what the new Carbon Modeller at L&F is tasked with doing.

It would be nice if L&F could tell us what in fact is going on in the department in this regard – and perhaps, how the department views the statement of Mr. Zwicker as a major client/manager of Crown lands.

At least one study for Nova Scotia, that by Cameron and Bush of Nova Scotia Environment (Bush has since moved to DNR/L&F), indicates quite the opposite of what Mr. Zwicker is suggesting (bolding is mine)

Are Protected Areas an Effective Way to Help Mitigate Climate Change? A Comparative Carbon Sequestration Model for Protected Areas and Forestry Management in Nova Scotia, Canada
By Robert Cameron and Peter Bush, 2016. The International Journal of Interdisciplinary Environmental Studies 11: 2329-1621. ABSTRACT Abstract: Protected areas have been proposed as a tool for mitigating climate change through carbon storage and sequestration. A C forest model was developed using carbon yield curves from the US Forest Service. The model was run on existing protected areas comprising 514,000 ha and 245,000 ha of proposed protected areas in Nova Scotia, Canada under three scenarios: 1. complete protected status; 2. forestry management which maximized timber yield; and 3. forestry management with environmental considerations. The model suggested 112 million tonnes of C is stored in existing and proposed protected areas and if protected these forests would sequester C over the next 130 years. If the proposed and existing protected areas were managed for forestry they would become a C source for the next 130 years for both maximum yield and forestry management with environmental considerations scenarios. There was a decrease of about 2 percent and 11 percent in total amount of C stored for forestry management with environmental considerations and maximum yield scenarios respectively. Frequent disturbance from clear-cut harvesting likely increases decomposition of organic matter in the forest which exceeds C sequestration by regrowth. The greatest advantage of protected areas is the greater certainty in land use and in maintaining the current and future C store.

I could not locate the exact source of the diagram presented by MZ, which is credited to – the Forest Products Association of Canada, however, that diagram and versions of it popped up in several forestry company Facebook pages and the like. FPAC is an advocacy organization and promotes wood construction and forest bioenergy as key components of the “Green Economy”. It offers little or no recognition (I could find none) of the well recognized issues surrounding the GHG emissions associated with forest bioenergy, e.g., there is no mention of abuses to be avoided such as those documented in Burned, the Movie and that we have experienced in Nova Scotia.

Perhaps the next diagram Mr. Zwicker posts and discusses will be of soil nutrient depletion in SW Nova Scotia and the implications for management. It is a topic well documented by L&F but which neither L&F or MZ/WestFor seem to want to discuss.

Some related links

Using forests to manage carbon: a heated debate
July 25, 2017 on
“Young, rapidly growing forests remove atmospheric carbon quickly, but have relatively small carbon reservoirs. Ageing forests capture carbon at decreasing rates, but build up large carbon reservoirs in biomass and soils. When an older forest is logged, not only the wood is removed, but carbon from unused biomass and soil is also released back into the atmosphere, creating a “carbon debt”. Especially large, old trees store most carbon, but are often over 100 years old. Repayment of the carbon debt may, therefore, take a long time.”

When old growth beats old school: New forestry technique imitates old growth to capture more carbon and profit
April 6, 2017, University of Vermont on
“Using an approach called “structural complexity enhancement”—a suite of forestry techniques designed to imitate the complexity of old forests and natural disturbances (like wind storms)—a team of scientist at the University of Vermont show that they can maintain high levels of carbon storage on managed timberland. Under this new style of forestry, the scientists report that, a decade after harvesting, carbon storage was just fifteen percent less than what would accumulate over time in forests that were not logged at all. In contrast, the study shows that conventionally managed timberland holds about forty-five percent less carbon than uncut forests.”

Protected Areas in Nova Scotia help to mitigate climate change, clearcuts do not
Post, NSFN May 26, 2017


From FPAC:

Tackle Climate Change Use Wood (No Date; ~2017)


Canadian Innovation in Bio-energy  (no date)

Bio-energy and Bio-chemicals Synthesis Report (2011)


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