General News · 15th February 2014
WHAT IS A FOREST ECOSYSTEM?
I believe that most of us now realize that a mature forest ecosystem is a complex community of interconnected, interdependent organisms demonstrably capable of developing, expanding and sustaining itself. To appreciate this, we only have to consider the forests that existed in much of North America and, more specifically, on our Pacific Coast, when we Europeans arrived.
These forests evolved in all their complexity from a bare landscape following the retreat of the glaciers around 10,000 years ago. Over the millennia, First Nation people may have altered these forests in many modest and generally localized ways, but overall; vigorous, mature forests dominated our B.C. landscape until very recently.
An old growth forest is a “closed loop” system. Nutrients and energy are continuously captured, generated and recycled within and between components in the system, increasing health, complexity and diversity through successive generations.
If we wish to sustain benefits from our forests, we must move beyond the focus on trees and consider the forest as an ecosystem. We must ask ourselves “What does it take to keep such a system healthy, thriving and able to maintain its long-term ability to provide those benefits we desire?”
PROBLEMS WITH MODERN FOREST MANAGEMENT
Planning for forest management deals very superficially with the complexities of the forest ecosystem and its long-term health. Economics drives most of the decisions and the issue of long-term sustainability is largely ignored or, if addressed, dealt with by simply suggesting that the planting of new seedlings will assure future crops.
There are a number of factors, which are seldom, if ever, mentioned in the forest management plans or in public discussion about forestry:
• The reduction of nutrients in the soil of the forest landscape as a result of harvesting trees,
• The role of epiphytes in the health and sustainability of forests,
• The role of mycorrhizal fungi in forest health,
• The benefits of healthy salmon runs,
• The concept of “waste wood”
I am assuming that it is self evident that each extraction of timber from a forested land base will remove, from the reservoir of nutrients and energy accumulated by the post-glaciation development of old growth forests in B.C., much of the nutrients and energy that it has taken to grow those trees.
Subsequent harvests will further deplete those resources unless fertilization occurs or there is sufficient time allowed for the various natural nutrient-accumulating components within a forest ecosystem to regenerate and replace those removed nutrients. Short-term harvesting rotations do not allow this to occur.
THE ROLE OF EPIPHYTES
I have read a study of the role of epiphytes in an old growth forest done by many forest researchers, including Gerry Franklin, a well respected Forester and educator in Washington State, reported in Discover magazine, November, 1995.
The study describes the hundreds of varieties of epiphytes (mosses, lichens and ferns) that live in a mature forest. They have the ability to take nitrogen (an essential element in the growth of plants) and other nutrients straight out of the atmosphere and into their tissues and, during their life cycle, pass these on to the forest floor where they become available to other organisms living within that ecosystem.
These studies have shown that epiphytes in a healthy, older forest steadily introduce nutrients into the system at a rate comparable to the amount a farmer would apply on his land to grow successive crops. These “free natural inputs” are permanently lost when successive harvests occur over short periods.
Why? Because when a forest is felled and harvested, the epiphytes die and release their contained nutrients within a few years. The epiphyte community is only slowly re-established in a young forest, taking 50 – 80 years to begin the process and 150 -250 years to regain most of the varieties that exist in a mature forest. Only when that point is reached is the epiphytic community again capable of delivering the nutrients needed to maintain and sustain a healthy forest.
THE ROLE OF MYCORRHIZAL FUNGI
The great majority of mycorrhizal fungi that permeate the soil and duff of a healthy forest are also engaged in beneficial symbiotic relationships with the trees through their root systems (for further details, see Paul Stamets book “Mycelium Running”). They are able to dissolve stone much more effectively that tree roots, gathering minerals and nutrients from the soil, then transferring them to the trees in exchange for sugars/carbohydrates created through photosynthesis.
The impact of harvesting trees, especially through clear cutting, on the populations of these soil fungi is unknown to me. I have not been able to find any definitive studies related to this question. The death of the trees that formed one half of the beneficial symbiotic relationship, along with the soil temperature increase from the timber harvesting, are just two factors that I suspect would be bound to negatively affect this evolutionary relationship.
I would welcome further information to help me better understand the impact of harvesting upon, and the time needed for recovery of, this beneficial symbiotic relationship.
THE ROLE OF SALMON IN THE FOREST
One other major source of significant “free nutrients” recently discovered to be available to older forests in the Pacific Northwest arrives where there are healthy annual salmon runs returning to the river systems. As salmon grow during their migrations through the oceans they collect a wide range of nutrients in their bodies. On their return to spawn, these are “distributed” into the landscape through the activities of their predators.
I have read that airline pilots, who regularly fly the Pacific Coastal regions, have easily noticed, looking ahead along their flight path, the much more vibrant green of the trees growing in the watersheds where there are healthy salmon runs; a visual illustration of the level of nutrients in those watersheds.
Salmon runs in many of the areas along our Coast have been negatively impacted, by conventional forest/fisheries management practices with the consequent loss of these free, valuable nutrients to the forest landscape. In forest management we need to adjust our practices to assist in the recovery of healthy salmon runs.
REMOVAL OF “WASTE WOOD” FROM THE FOREST
The prevailing attitude that any woody material that remains on the forest floor following timber harvesting is “waste” and should be used in one way or another. Either that, or it should be piled and burned to ease replanting. The unintended result is similar to that of the “scorched earth” policies that were often occurred in past wars; removing support for life from the landscape.
The idea of using “waste” is understandable from an anthropocentric perspective but ignores the reality of what is required to sustain a living system like a forest.
The removal of as much wood as we can use greatly diminishes the nutrients and energy available to grow future generations of trees and the complex of other organisms that make up a healthy ecosystem.
In addition, I suspect that, if we analyzed the whole process, we would conclude that the energy derived from the utilization of waste versus that expended in generating that energy would be a negative result.
If we truly wish to have sustainable forests it would be much more beneficial to leave much of what we now categorize as “waste” in the woods to be recycled and incorporated in succeeding generations.
(Ideally, I would suggest that we should be processing our trees in the forest, taking only those parts that we need and leaving the “waste” behind to be broken down by natural means and recycled.)
NATURAL INDICATORS FOR SUSTAINABILITY
HUMANS AS PREDATORS IN THE FOREST
When I look at the impact of modern forestry activities on the forest ecosystem, I have come to the conclusion that the dynamic is effectively a “predator/prey” relationship (P/PR). A predator extracts energy/nutrients from a prey population, having an impact that is directly related to the level or degree of predation. This, in turn, determines whether or not the relationship will be cyclical or stable as well as sustainable over time.
In the mid- 90’s, a friend mentioned having seen a program on “the Nature of Things” on CBC television of the interaction between the peregrine falcons and the ancient murrelet seabirds during their reproductive season on Haida Gwaii (the Queen Charlotte Islands). He told me that after seventeen years of study, the scientists had recorded an average predation rate by the falcons of the seabirds of approximately 15 – 20 % of the “annual incremental growth” of the ancient murrelet population.
This got me started thinking along the lines of the harvesting of timber from the forest as being a P/PR. I began looking for studies of further examples in the natural world to see if there was a common level of predation that has proven stable and sustainable.
In addition to the falcon/seabird example above, I have found two more studies (polar bear/ring seals and leaf cutter ants/vegetation growth) and know that there will be others that people with superior investigative skills to mine could discover.
These three examples demonstrate a reasonably consistent predation rate ranging from 15 to 21% of the annual incremental growth of the prey population that has proven, over time, to be sustainable.
On a very personal level, I look at my own body as a complex, interconnected, interdependent system and ask myself “How much of the energy and nutrients that I accumulate would I would be willing to sacrifice to a predator within my system before I would feel unsustainable?”
I feel that I could probably tolerate an “extraction rate” of around 15 -20% and still carry on but, if much more were taken, I would feel like I was on a slow or rapid “downhill run”.
On a cautionary note, our forest practices are more negatively impacting than typical P/PR activities. We not only kill the trees and disrupt many supportive ecosystem relationships, but we almost always entirely remove the energy and nutrients represented in the timber we harvest from the ecosystem. Other P/PR activities in nature generally result in the energy and nutrients remaining in and recycling within the ecosystem.
These considerations lead me to conclude that a harvesting rate of 15 – 20% of the annual incremental growth of forests would be a useful, nature-based and meaningful guideline in the development of sustainable forest management plans.
I consider that for any renewable resource to be considered truly sustainable, it must endure for a long time. In the case of forests, I would suggest that we should be looking at a time frame in terms of millennia, not simply the next generation of trees.
I have come to the conclusion that we need to radically revise our approach to forest management if we truly wish to have forest ecosystems sustainable and the benefiting present and future generations.
February 15, 2014