Pattern #1 - Disturbance can be good

WEDNESDAY - I've been watching the rains fall hard all day outside the library window as I work, round two of flooding in the region as we receive the effects of Hurricanes moving up the east coast. This is the second series of heavy rains, flood warnings, and fears of considerable damages to infrastructure amongst a time when towns, cities, and states are struggling to pay the most basic of bills.

This past weekend I was in the Adirondacks hiking with my girlfriend Liz and our two dogs and she made a keen observation as we climbed over and circumvented around hundreds (yes, hundreds) of downed trees that were victims to the recent high winds and heavy rains from Hurricane Irene. She noted that from her understanding, the relatively infrequent nature of these disturbances seemed to be a good thing for the forest while proving to be devastating to anything human-engineered; roads, farms, bridges, etc.

This gap is the landing area for a logging operation, and while it may seem destructive is the source of many healthy young trees that are the next generation in the woods.

Indeed when we look at events that change ecosystems dramatically - often referred to as disturbances in ecology - we see that while the impacts may seem detrimental at first, they tend to have a beneficial impact in the long term. Take the blow downs we witnessed in the Adirondacks - should we see them as a devastating loss for the forest, or is it nature's way of thinning out inferior trees, opening up light gaps in the canopy, and feeding the forest floor with an abundance of biomass?

While it may be clear that I am biased toward the latter opinion in this case, by and large the jury is still out. What we do know is that disturbances (fires, floods, ice storms, etc) definitely happen, that certain species and ecosystems are adapted to disturbance and need it to thrive; and that some disturbance appears to be beneficial in increasing biodiversity, while too much of it does not allow for ecosystems to recover and sustain themselves in the long term.

So...all this toward my first attempt at adding a pattern to the language. For more background on the pattern language I am working on you can see last week's post.

Here is my summary of the pattern, named Design for Disturbance (for now...):

PROBLEM: The phenomena of disturbance is often interpreted as having a negative impact on ecosystems, and human-designed ecosystems are mostly devastated by large disturbances. This is due to our short sighted thinking and lack of design which accepts and anticipates disturbance.

THEREFORE,

1. Disturbances should be accepted as an inevitable part of succession and designed for through building ecosystem resilience. 

2.Disturbances on multiple scales can be human-driven in some cases to benefit the ecosystem in the longer term.

I'll touch on a quick example of #1. While this example touches on #2 we will get into it in more depth next week.

The recent storms in those Adirondack woods were, in effect, a large thinning of inferior species by mother nature, who removed forcibly a number of trees that would likely not live in the long term.

An intervention by thinning out these inferior trees BEFORE the storm hits would have likely increased the number of residual healthy trees. For example, if you had 300 trees on an acre those trees feel an increased amount of stress and competition for light, water, and nutrients as they grow up. Thinning to 100 trees/acre means less overall trees, but that the remaining are able to grow deeper root systems and access all they need to grow. 

Too dense? Just right?

The challenge in thinning is finding that balance between too much and too little. If you overthin a stand, the residual trees may have too much space and the effects of a heavy wind blow could end up devastating the stand. The optimal density depends on many factors, from soil to tree species to the aspect of the site.

A forest with a lot of the same species can also cause challenges. A monoculture stand of plantation pine planted all at the same time is much more susceptible to many disturbances (disease, wind, invasive species) versus the benefits in structure, texture, and resistance to disease with a more mixed species, and mixed aged stand of trees.

Ok, that's all for now. If you come across any readings or research to help develop these thoughts, please pass them my way. 'Til next week...