[APWG] Fw: Ideas for thought.

[Marc Imlay]

I once read a review on fire managed ecosystems maintained for millennia by
the original inhabitants in the East. Fortunately, they managed natural
fires rather than setting new fires.  Cheers.
 
Marc Imlay, PhD

Conservation biologist, M-NCPPC

Board member of the Mid-Atlantic Invasive Plant Council,

Hui o Laka at Kokee State Park, Hawaii

Vice president of the Maryland Native Plant Society,

Chair of the Biodiversity and Habitat Stewardship Committee

for the Maryland Chapter of the Sierra Club.


  _____  

From: apwg-bounces at lists.plantconservation.org
[mailto:apwg-bounces at lists.plantconservation.org] On Behalf Of Ty Harrison
Sent: Tuesday, April 05, 2011 3:26 AM
To: apwg at lists.plantconservation.org
Subject: [APWG] Fw: Ideas for thought.


Please find below an interesting essay by Toby Heminway, the polyculture
guru,  which members of APWG may like to discuss.  Some of his points
deserve a critical analysis.  I'm not sure we can accept some of his
generalizations. Are we really wasting time and money figting invasives?
Regards,  Ty Harrison

Native Plants: Restoring to an Idea

Thursday, December 02, 2010 3:44 PM

Let me tell you about the invasive plant that scares me more than all the
others. It's one that has infested over 80 million acres in the US, usually
in virtual monocultures. It is a heavy feeder, depleting soil of nutrients.
Everywhere it grows, the soil is badly eroded. The plant offers almost no
wildlife habitat, and since it is wind pollinated, it does not provide
nectar to insects. It's a plant that is often overlooked on blacklists, yet
it is responsible for the destruction of perhaps more native habitat than
any other species. Research shows that when land is lost to this species,
native plants rarely return; they can't compete with it. It should go at the
top of every native-plant lover's list of enemies. This plant's name: Zea
mays, or corn. Corn is non-native. It's from Central America. Next on my
list is the soybean, with 70 million acres of native habitat lost to this
invasive exotic. Following those two scourges on this roll call of
devastating plants is the European invader called wheat.

Wait, you say: these plants are deliberately spread by people; that's
different! But to an ecologist, it is irrelevant that the dispersion vector
of these plants is a primate. After all, we don't excuse holly or Autumn
olive, even though without bird dispersal, they could not spread. Why are
corn, soy, and wheat not on any blacklists? Because we think of them
differently than plants spread by non-humans. This suggests that an invasive
species is an idea, a product of our thinking, not an objective phenomenon.
When we restore land, we restore to an idea, not to objective criteria.

Let me give another example of how our ideas dictate which species we'll
tolerate and which we won't. The wooded hillside on rural Oregon where I
once lived was thick with 40- to 120-year-old Douglas fir and hemlock.. But
as I walked these forests, I noticed that scattered every few acres were
occasional ancient oak trees, four to six feet in diameter, much older than
the conifers and now being overtopped by them. I realized that in these
ancient oaks I was seeing the remnants of the oak savanna that had been
maintained for millennia by fire set by the original inhabitants, the
Calapuya people. The fir forest moved in when the whites arrived and drove
off the Calapuya, and suppressed fire. So what I was seeing was a conifer
forest created by human-induced fire-suppression, and it had replaced the
oak savanna that had been preserved by fire setting. Which was the native
landscape? Both were made by humans. If we say, let's restore to what
existed before humans altered it, we'd need to go back to birches and
willows, since humans arrived as the glaciers retreated. But clearly that's
not appropriate.

In a similar vein, one of the rarest and most valued ecosystems in the
Northwest are the native prairies, such as those found in the Willamette and
other valleys. Yet these prairies are also the product of human
manipulation. Prairies occurred naturally in the Willamette over 5000 years
ago, but began to disappear after that. Ecologist Mark Wilson has written
"As climate turned cooler and moister 4,000 years ago, oak savanna and
prairie ecosystems were maintained only by frequent fires set by native
people to stimulate food plants and help in hunting." The local people used
fire technology to maintain an environment that supported them even when the
climate no longer supported that ecosystem.

So I applaud and encourage efforts to preserve native prairie in the
region-they are valuable as endangered species habitat, examples of cultural
heritage, and a way of preserving planetary biological wisdom. But we should
restore these prairies with the strict recognition that we are creating-not
recreating or restoring--a state that can not be supported by current
climate and other conditions. Prairies are artificial in the Willamette
Valley. The preservation of prairies there isn't a matter of simply
repairing and replanting a degraded landscape and then watching the prairie
thrive, but constructing a species community and an environment for it that
must remain on intensive life support, with constant intervention, for it to
survive at all, as long as the climate remains unsuitable to it. The
Willamette prairie remnants can't be considered native; the only criteria
they meet is that they were here in small patches when botanists first
catalogued them. But so were dandelions. Botanists knew dandelions weren't
native, but the didn't know that the prairies were human created, so the
prairies were catalogued as native. Prairies in the Northwest haven't been
indigenous for 4000 years.

We love the local prairies and I firmly believe in the efforts to preserve
them. But I want us to be clear that we are restoring to an idea. We are
restoring because we want these things here, and not because there is a
master blueprint that says they are the right ecosystem for the place.
Ecosystems exist because current conditions favor those particular
assemblages. Change the conditions, and the ecosystems will, absolutely,
change. Both the climate and humans have changed the conditions plenty.
Environmental change is the driving force behind shifting species makeup.
With plants and most animal species, no evil species showed up and through
sheer cussedness, killed off the locals. Instead, the conditions changed

The very concept of wild land, for most Americans, is founded on a
misunderstanding: a very brief ecological moment during which a once-managed
ecosystem was at the height of its degradation due to loss of its keystone
species. The dark and tangled primeval forests, written about by Thoreau and
Emerson, are simply the declining remnants of open and spacious Eastern food
forests, turned to thicket after a century or two of neglect. But this idea
of wilderness is deep in our mythology, national imagery, and consciousness.

Let's look at some of the causes of species change. First: terminology. The
word "invasive" is loaded. We hate invaders. The term also places focus
solely on the incoming species, yet the ability of a species to survive is
due to interactions with the biological and physical environment. So I
prefer a more neutral, and I think, ecological more correct and descriptive
term, such as opportunistic. Kudzu is not much of a problem in its native
habitat, but it will take advantage of opportunities.

What creates those opportunities for species shifts? Intact ecosystems are
notoriously hard to invade. We know this because, for example, seed
dispersal rates are truly astounding.. Birds are a major dispersal agent.
They can carry seeds from multiple plant species in their gut, stuck to
their feathers, and in mud on their feet. So picture billions and billions
of birds, for 60 million years or so, traveling tens to thousands of miles,
seeds dropping off of them every wing-beat of the way. Add to that bats,
which are actually more effective at seed dispersal, per bat, than birds.
Plus land-animal dispersals, not as far-ranging as birds but bringing much
larger seed loads via droppings and fur. Include water-rafted trees and
other plants, wind-dispersed species, and more.

This gives a picture of the whole planet crisscrossed with billions of birds
and animals for millions of years, seeds and spores going everywhere, eggs
being carried to new environments, dispersal, dispersal, dispersal! So why
isn't the whole planet a weedy thicket? Because the mere arrival of a new
species, even in large numbers, is not what causes a successful
colonization. Ecosystems are very hard to invade, and several conditions
must be present for that to happen.

A major reason for ecosystems being tough to invade is that nearly all the
resources in undisturbed ecosystems are being exploited. Nearly every niche
is filled, every nutrient flow is being consumed, almost every opportunity
is taken. Two major changes make ecosystems invasible: disturbance, and the
appearance of new resources. Take disturbance. Perennially disturbed places,
like riparian zones, are sensitive to opportunistic species. So is farmland,
or developed areas, or anywhere than humans or nature cause disturbance. It
drives me nuts when I read that "species X" has destroyed 50,000 acres of
habitat. When you do a little digging you find that, no, that area was
farmed, or new roads cut, or logged, or polluted, or otherwise disturbed,
and then the new species moved in.

For example, one poster child of invasion biologists is the brown tree
snake, blamed for invading Guam and killing off several species of birds.
The untold story is that for decades the US Navy used over half of the
island as a bombing range, leaving most of it unfit for life. Much of what
remained was crowded by displaced people, and developed by the military, and
thus turned into poor and disturbed habitat. The tree snake just cleaned up
the struggling remnants that were already in serious decline.

Stop the disturbance, and you'll almost always eliminate or reduce the
effect of the new species. Land I lived on was clear-cut in the early 1970s
and not replanted with fir until the 1980s, and was covered with patches of
Himalayan blackberry and Scot's broom when I arrived in the early 1990s. By
the late 1990s, both species were gone from most places and nearly dead
everywhere else, because the trees had grown back and shaded them out. The
problem is disturbance, not that a species pushes out others because it's
tough or mean.

This suggests that we need to take care of naturally disturbed areas like
riverbanks, since most of the species we've labeled as problematical thrive
on disturbance. Even in these riparian zones, though, conditions are altered
from what they once were because of the loss of the beaver and from damming.
Thus nature is just trying to deal with our changes as best as she can, and
she'll use whatever resources she can find. A return to the former, natural
disturbance regime may allow the once-present vegetation to return, if that
is our choice for that land,

The second cause of successful invasion is the appearance of new resources.
Often the new resources that that allow an otherwise intact ecosystem to be
colonized are pollution and fertilizer runoff. For example, a number of
aquatic opportunists, such as purple loosestrife, thrive in more polluted
and higher-nutrient environments than the plants they replace. Many species
that evolved in clean water are harmed by pollutants. Loosestrife, though,
has high rates of nutrient uptake, and this trait allows it to out-compete
many other species in polluted water.. But in permaculture, we say that that
every problem carries within it the seeds of its own solution. And so
loosestrife can be used in constructed wetlands and in natural environments
to clean nutrient-rich water. They are an indicator of a problem, a response
to it, and nature's way of solving a problem, not the problem itself. If you
really hate loosestrife and want it to go away, clean up the water. Without
doing that, you'll be flailing away at the problem forever. Spraying and
yanking is not an effective strategy to remove unwanted species. Nature is
far more patient and persistent, and has a bigger budget, than we do. To
remove an unwanted species, change the conditions that made it more favored
than the desired vegetation.

Unwanted species generally arrive because humans have changed the
environment to make conditions more favorable for the new species. And when
we "restore" landscapes, or more often, introduce a set of species that we
have decided are the ones we want to see there, we are altering the
landscape to suit our idea of what should be there, not to match some divine
plan. These two understandings burden us with a huge responsibility to make
intelligent choices, but more importantly, to recognize that we are often
arbitrarily making a choice based on our own preferences, not because there
is only one right choice for a landscape, When we put resources into
landscape management, however, we direct the shape of that landscape toward
only one choice. That's the best we can do. Thus I'd like to see us be less
dogmatic in the way we cling to those choices.

Unfortunately, dogma is present on all sides. Friends of mine approached the
Portland city government with a plan to create some edible plant corridors
along Springwater Trail, a 40-mile bicycle and pedestrian loop around the
city. Their idea was for bikers and pedestrians to be able to snack on
berries and fruit. The city official in charge said, "Nope, we have a
natives-only policy on the trail." The trail is a paved pathway that goes
through industrial areas and along backyards, road right-of-ways, and
scrubby vacant lots. It probably goes through a dozen or more different
environments, based on soil, water, sunlight, and all the other factors that
determine what plant communities will grow there. But the policy is natives
only. Wouldn't it make sense for the primary species that will be using that
trail to have a habitat that suits that species' needs for food and comfort,
particularly since it's in a busy urban area? But instead the landscaping is
to be driven by an idea, by dogma. I totally support the idea of having
natives-only areas on the trail. But let's allow the new landscaping to
serve those that it's being built for, too.

I began this with corn and soybeans. One of my favorite snarky questions for
natives-only people is: "What did you eat for breakfast?" I ask that because
it is our choices that determine how much of our landscape is going to be
consumed by non-native species.. I didn't eat camas cakes with
pink-flowering currant syrup this morning, and I'll bet you didn't eat any
local plants either. Of course, I'd rather see someone growing indigenous
species in their yard rather than having a sterile, resource gobbling lawn.
But my Portland yard is not, in my or several other lifetimes, going to be
part of a natural ecosystem. I might be able to cultivate some endangered
native species in an attempt to pull a rare plant back from extinction.
That's one good reason I can see for growing indigenous plants in my yard.
But the most frequent native plants I see grown in yards are salal, Oregon
grape, and others that are in no danger of extinction and don't, to my
knowledge, support specialist species dependent only upon them. And since
much of my yard is watered, it is inappropriate for me to grow natives that
are adapted to our dry summers. It's always stuck me as bizarre to see
Northwest natives being irrigated.

But even more than indigenous plants, I'd rather see someone providing for
some of their own needs from their yard. When we eat a bowl of cornflakes
for breakfast, or oatmeal, or store-bought eggs, we are commissioning with
our dollars the conversion of wild land into monoculture farms. I'll bet
that a large percentage people reading this buy local food, shop organic,
and so forth. But the farms growing that food are almost all moncultures,
and out of the urban matrix. In other words, it is farmland that, if
consumption decreased, has a far better chance of being restored to a
functioning ecosystem than a home lot. If I grow some of my own food, that
means that somewhere out in the country, a farmer won't have to plow so
close to the riverbank, or could let some of that back field go wild. That
land has a far better chance of functioning as an ecosystem than my yard
will. Oh, I have visions of how city and suburban landscapes could be
functional ecosystems, but that's another subject.. My point is, we need to
be putting money and energy into growing indigenous species where they will
do the most good, where they can truly contribute to ecosystems and their
functions. Much of our efforts in eliminating exotics is a complete waste of
resources at best, and at worst is a terrible use of poisons to destroy a
hybrid habitat whose function we don't yet grasp. Let's be honest at what we
are restoring to: an idea of what belongs in a place. If we want to get rid
of an invasive exotic, let's get rid of some monocultured corn, and let a
bit of farmland return to being a real ecosystem.

Copyright 2007 by Toby Hemenway

(presented at the Native Plants and Permaculture Conference, Lost Valley
Educational Center, Dexter, Oregon, in May 2007.)


 
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