Sun rays penetrate a forest

Indicators in Nature as a guide for achieving sustainability in our forests

The complexities inherent in a healthy forest ecosystem and the variety of approaches that can be used to manage forests make it appear very challenging to choose a management approach that might achieve health and long term sustainability in our forests. 

However, the fundamental requirement for any ecosystem, large or small, complex or simple, to restore functioning and remain healthy over time comes down to nutrients. 

If it is able to acquire/generate sufficient nutrients to maintain its interconnected, interdependent community of organisms and their functions it will thrive. If not, it will either slowly diminish or die out and be replaced by some other type of system. 

Mature forest ecosystems generate more than enough nutrients to thrive, with excess being stored structurally or in the forest soils. The Pacific Coast Temperate rain forests were sustainable, following the last glaciation, with the harvesting levels that sup- plied the needs of Indigenous people. 

However, as demands for timber grew, exports rose, technology advanced and harvesting rotation periods have diminished, ex- traction rates have risen to the point where these ecosystems are increasingly being degraded and are patently no longer sustainable. 

Following a harvest, most of the nutrients needed by the slowly regenerating young forest are derived from accumulations stored in the landscape from previous generations. Given sufficient time, a wide diversity of organisms re-establish themselves in complex, interconnected and interdependent relationships that are increasingly able to generate the nutrients necessary for sustaining a healthy, complex forest ecosystem. 

Forest soils accumulate very slowly, suggesting that the “surplus” nutrients are a small proportion of the total that is produced, with the larger proportion supporting the ongoing requirements of all the organisms living within the ecosystem. 

A healthy, fully-functioning ecosystem can tolerate losing some portion of its regularly accumulating nutrients but it also requires that a substantial portion remains within the system to ensure its ongoing health. 

Unless ecosystems are managed to grow beyond the age when the nutrients are being extracted by the newly growing forest and well into the later stages when nutrients are being accumulated, the forest system and landscape will be repeatedly degraded by each short rotation harvest. 

Unfortunately this is what is happening in British Columbia. There is growing recognition that the impact of conventional forest man- agement, exacerbated by the shortening of the “rotation age” (of- ten now down to 30 – 60 years between harvests), is removing far too many of the nutrients from these forest landscapes for them to be sustainable. 

The fundamental question remains – how much of the accumulat- ing nutrients in the ecosystem can be extracted in any form, be it timber or biomass, without slowly or rapidly reducing its ability to remain healthy and sustain itself over time? 

The answer exists in nature and its sustain- able ecosystems. 

While it is difficult to find any examples of human managed forests that have proven to be sustainable over millennia, in the natural world, there are many “consumptive” dynamics that have been functioning sustainably within ecosystems for thousands or millions of years. These can provide a useful indicator as to what proportion of the accumulating nutrients might be sustain- ably removed under the management guidelines. 

Looking at the examples found (see below) of those sustainable relationships that have been quantitatively studied, a consumption rate of between 15 and 22% of the Annual Incremental Growth of the consumed has been demonstrated. 

Harvesting timber from a forest is also a consumptive activity but, even more, is an extractive one, as it mostly removes from the forest ecosystem the nutrients required to grow the timber har- vested. In a natural system almost all of the consumed nutrients remain in and are recycled within the ecosystem. 

BENEFITS of the 15% of MAI APPROACH

  • Our Provincial forests will, barring unforeseen catastrophic changes, be sustainable in perpetuity, satisfying the needs of future generations. Eighty-five percent of the annual accumulation of nutrients will remain in the ecosystem to maintain its health.
  • The harvest volume will be responsive to positive or negative changes of the MAI in our forests found through regular updating of data from permanent sample plots.
  • This provides a simple, understandable and measurable foundation for the creation and implementation of an Ecosystem Based Management plan for our forests.
  • The regular annual harvest of timber from Provincial Forests will provide a stable foundation for development of a robust value-added economic sector in B.C.
  • Size, quality and value of timber harvested and made avail- able to entrepreneurs for processing and value-adding will increase over time. Local economic benefits will grow signifi- cantly as competing large, high quality timber from other sources diminishes.
  • The forests will age relatively quickly as the “rotation age” for the timber harvested will be in the 250 – 300 year range.
  • Provincial forests will gain many “old growth” characteris- tics as the portion of the forest that is outside the Timber Harvesting Land Base (THLB) ages and areas within the THLB will incorporate “full cycle” and rotation age trees.
  • Epiphytes and mycorrhizal fungi, potential major sources of nutrients for an older ecosystem, will have adequate time tore-establish healthy populations.
  • The forest will become more biodiverse and robust as it ages, improving resilience and its ability to respond to the impacts of global warming and climate change.

Conclusion

Giving consideration to the indicators from the studies of sustain- able “consumptive“ relationships mentioned below and given that timber harvesting is not a closed loop paradigm (where nutrients remain within the ecosystem), the average annual harvest should be limited to about 15% of the Mean Annual Incremental growth (MAI) within any forest ecosystem. 

Current harvesting rates in British Columbia are grossly in excess of a long-term, sustainable level and need radical reduction, if we truly wish to hand sustainable forests on to future generations. 

Reference material: 

  1. Verbal report about a 1989 CBC “Nature of Things” program on 17 year studies of the Peregrine Falcon/ Ancient Murrelet relationship in Haida Gwaii. The scien- tist found a predation rate by the falcons of around 15 – 20% of the annual growth of the Ancient Murrelet population, which appeared to reflect a sustainable re- lationship over time.
  2. Prof. Ian Stirling, Univ. of Alberta, polar bear specialist, has found predation rates by polar bears of ring seals (95% of the bears annual food) to range between 15 and 22% of the annual incremental growth of the seal population.
  3.  An article in the New York Times on Aug 3, 1999 by Nicholas Wade stated that: “Biologists believe some 15 percent of the leaf production of tropical forest disappears down the nests of leaf-cutter ants”. Leaf cutter ants have existed for over 50 million years, providing an excellent example of a sustainable consumptive relationship.”
  4. Prof. Tom Reimchen, U.Vic., quotes in his article entitled “Some Considerations in Salmon Management”, studies, done for over 40 years by A.R.E. Sinclair, of the population dynamics in the Serengeti concluded that “In the Serengeti, the social and solitary cats take about 16% of the total prey biomass”.
  5. Opinion of Herb Hammond, RPF (Silva Forest Foundation) and referencing Prof. Jerry Franklin, (University of Washington), March, 2014. “I have thought about this issue for 3 decades and had many discussions with practitioners and scientists about this question. Jerry Franklin, new forestry guru at U of W, and I have discussed this on many occa- sions. Our intuitive belief is that not more than 25% of the MAI is “surplus” to ecological function over the long term. Having said that, before forestry got started, natural forest ecosystems utilized all of the MAI annually to maintain the system. So, removing a maxi- mum of 15-20% of the MAI is a sound, conservation- based approach.” 
  6. . Article by Briony Penn (2016) entitled “Fast Bird, Slow Food” about the traditional exploitation of the Sooty Shearwater colonies on islands off South New Zealand that “shows the traditional rate of harvesting oscillates around an average of 18 percent of eggs and chicks annually, a rate that has sustained that traditional food system for well over 700 years.” 

Top image credit: Forest scene by Photo by Sebastian Unrau on Unsplash

Sign-up for Cortes Currents email-out:

To receive an emailed catalogue of articles on Cortes Currents, send a (blank) email to subscribe to your desired frequency: