Bissell:
> The term "patch" is relatively new in ecology. It is used in a couple of
> ways, but most commonly as a sub-unit of either ecosystem or biotic
> community. In most cases it is meant to mean a relatively small unit of
> vegetation within some larger group. Like a meadow in a forest.

This really depends on who is using the term 'patch'. For instance in a
disturbance regime where wildfire is frequent, the patch may be as large as
240,000 hectares. The patch in a rainforest where a group of trees is blown
down by wind is often only one quarter hectare in size. In the first
example, a boreal forest, the disturbance is referred to as a patch simply
because from a distance it looks similar in composition, has the same or
similar history, but in reality there may be 'patches' within the Boreal
forest patch that vastly exceed the size of the windthrown patch in the
rainforest. So on the one hand the definition of a patch in the rainforests
is minute in comparison to the patch as defined in the boreal forest....

So much of the discourse on patch size, patch retention and definition
consists of a 'social construct' that requires 'deconstruction'.  For
instance a patch made by clearcutting and planted immediately is vastly
different than a natural regenerated patch that was killed by insects. In
terms of wildfires too, it is now very difficult to determine what is a
natural rate of wildfire frequency, as well as what is a natural patch size
in the sub-boreal forest because the composition of much of the forest is
now much different than it was prior to Europeans arriving here.

During the Gold Rush and up until the time of the completion of the
railroads vast areas of forest were simply burned off. One of the galling
consequences in the Yukon has been the virtual elimination of old growth
climax spruce forests in the low elevations along rivers. The majority of
the forests in center of British Columbia in the western and southern
portions of the Prince George Region where a complex mosaic of age classes
(old and young), but these were replaced by frequent and large scale stand
replacement events associated with anthropogenic fires caused firstly by
miners who simply wanted some dry firewood, or easy country to prospect in.
When the settlers came they to burned off the forests so as to increase
grazing opportunities, and of course the old steam locomotives were
notorious for starting wildfires.

Because of this 'change' in the distribution of age classes toward a
predominately young pioneer forest composed of mainly of lodgepole pine
versus alpine fir and spruce, the forest has lost it's resilience to
stresses caused by insects like the lodgepine pine bark beetle. Currently
this insect is decimating millions of hectares of mature lodgepole pine in
the Prince George, Prince Rupert and Williams Lake Region (an area larger
than France and Germany). The effects of this 'anthropogenic' based change
in the regional ecology will be a negative feed back, more wildfires,
accelerated harvest of affected trees, and a gradual change toward a very
unsteady state (dis-equilibrium) of more young lodgepole pine dominated
forests. By reducing complexity and diversity, the tendency toward
maintainance of homeostatic buffers (tree species and age diversity) is
truncated much too early. The long term outcome will be seen in reduced
predation of insects by insectivorous birds, fewer parasatoids of bark
beetles, younger and younger trees being attacked, dense immature almost
continuous single age classes, all leading to a sort of perpetual
dis-equilibrium where man is required to introduce biocides such as
arsenical insecticides in individual trees which are attacked.


Of course stability and equilibrium is desireable for humanity becuase
industry relies on it, but it is not capable of maintainence of it yet. The
forest industry here refuses in large part to accept the ecological limits
of clearcutting, and even has launched numerous attempts to log parks as big
as Tweedsmuir Park on the justification that in order to save the forest
from devastation by bark beetles it will be necessary to harvest the live
attack trees in all Parks. And they have succeeded so far on a small
scale...but the facts about the role of anthropogenic disturbances is not
going to change the beetle epidemics which are now attacking smaller and
smaller diameter trees.











>
> As to whether or not this discussion has been over terms, I tend to think
> not. At one time the idea that ecosystems, biotic communities and such
were
> governed by certain rules and that those rules were largely deterministic.
> In other words, an ecosystem was a highly stable unit, which was
undergoing
> slow change toward a defined state; the climax state. Given this view, any
> change other than the "natural" changes of the ecosystem can be view as
> "bad." The other view that ecosystems are largely stochastic, in other
words
> not progressing toward any certain state, but rather changing in random
> ways, allows some induced changes. The first view has some intuitive value
> in that you can simply label all human change as "bad." The second view is
> more difficult because it allows for change, but means you have to
determine
> how much change, when, where, all that sort of thing.
>
> Are ecosystems real or conceptual? Well, I suppose in some ways they are
> both. You can take the concept of ecosystem in the field and use it to
> determine the unit of study, or management, or policy. Once a unit is
> labeled an "ecosystem" in policy it does take on a legal reality, which
can
> be good. For example there was an effort to define a large area around
> Yellowstone National Park the "Yellowstone Ecosystem" back during the Bush
> the First's reign. It got several top level Federal Government policy
people
> fired. If it had gone thru, there would have been a "real" ecosystem. I
> don't have other examples, but I guess my answer is that ecosystems are
not
> fully real, but they are not merely conceptual either.
>
> Hope this clarifies my point of view Ray, thanks for asking.
>
> Steven
>
>  "Our human ecology is that of a rare species of mammal in a social,
> omnivorous niche. Our demography is one of a slow-breeding, large,
> intelligent primate. To shatter our population structure, to become
abundant
> in the way of rodents, not only destroys our ecological relations with the
> rest of nature, it sets the stage for our mass insanity."
>         Paul Shepard
>
>
> -----Original Message-----
> From: Discussion forum for environmental ethics.
> [mailto:[log in to unmask]]On Behalf Of Ray Lanier
> Sent: Monday, October 29, 2001 12:21 PM
> To: [log in to unmask]
> Subject: Re: Ethical implications of environmental change
>
>
> Folks,
>
> Interesting discussion.  Tenatively, I'm inclined to think that you folks
> are talking past each other.   I may be wrong, but it seems to me that you
> folks generally agree about the way the overal system operates but are not
> in agreement about what to call the subsets and how they might be defined.
> But then, I'm no ecologist etc.
>
> It would be helpful to me if someone would define the several terms that
are
> being used and the relationships among them.  For example:  landscape,
> ecosystem, patch, and others that you see as relevant, in your
professional
> views.  Or is that too big a question set?
>
> Guidance would be most appreciated.  And please continue the discussion.
>
> Sincerely,
>
> Ray