|
Keystones
and Cops: An
Eco-Mystery Thriller
by Peter Bane
If you'd just witnessed the
crime of the century and you
thought you knew the culprit
and the story, wouldn't you
be eager to tell it? No, I don't
mean Dubya and the Twin Towers
- that one's already been figured
out, but another story, from
another century, copiously reported
but equally misunderstood.
Ninety-nine years ago, also
in New York, officials identified
a sinister Asian invader as
the cause of what would become
the catastrophe of modern North
American history. Livelihoods
would be devastated, vast tracts
of the country depopulated,
violence and crime would explode
in the wake of the disaster;
whole communities were dragged
into drug trafficking. Slow
at first to react, the nation
soon grasped the full implications
of the tragedy. A crash program
to defend the homeland was launched
with support of the government
in Washington. Restrictions
on transit were imposed. Chemical
warfare was initiated. A scorched
earth policy was attempted but
ultimately failed because the
enemy was too wily. Escaping
from the government legions
sent to hunt it down and contain
its villainy, the menace reproduced
invisibly and spread rapidly
throughout the population, wreaking
havoc with the economy.
For a more innocent and optimistic
America, Cryphonectria parasitica
was the Osama bin Laden
of its day. A cruel and ruthless
murderer, it would ultimately
slay one in every four American...
...trees. Chestnuts: the dominant
tree of the Eastern forests.
Four billion in number, ranging
from Maine to Mississippi with
outliers in the Midwest, they
comprised 25-40% of the mixed
deciduous hardwoods. Called
"Redwoods of the East"
because of their towering height
and immense girth (some reached
20 feet in diameter, over 100
feet in both height and spread),
the trees formed the backbone
of the rural economy over the
full length of the Appalachian
Mountains and foothills. Valued
for their straight-grained,
lightweight, and rot-resistant
timber; the tannins from their
bark and wood; and for their
tremendous crops of sweet, delicious,
nuts avidly eaten by humans
and wildlife alike; the Chestnut
was without peers in the vegetable
kingdom. Today, all that remain
are millions of shrubby stump
sprouts (some trees not killed
entirely have put up new shoots,
but these succumb to the disease
after a few years), a handful
of erratics in unique situations,
and a small number of declining
groves in Wisconsin and Michigan
that were late to be infected:
Victims of the blight, every
one.
Every school child in America
hears this story sooner or later.
It's been repeated in thousands
of publications. It's old news,
a tragedy long past, if not
forgotten: perhaps an early
harbinger of America's fall
from grace. For the record there
are new and promising developments,
too. Chestnut enthusiasts began
breeding blight resistance (from
Asian chestnuts, the presumed
agents of infection) into American
chestnuts in the late 1970's
and expect to have a quantity
of blight-resistant seeds and
trees for planting out by 2005
or 2006. [1] Other groups have
been working to diminish the
virulence of the pathogen by
inoculating infected trees with
another fungal agent from Europe
that renders chestnut blight
much less harmful, thus allowing
the tree to survive and reproduce,
a process known as hypervirulence.
[2] There have even been attempts
to bioengineer the disease to
limit its destructiveness. These
are worthy efforts and the individuals
involved are dedicated visionaries,
but let's step back for a moment
from the drama of loss and recovery
to examine what may have been
behind this shocking set of
events.
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Understanding
the Terrain
To develop a full sense of the
crime that happened to the American
chestnut (Castanea dentata),
we have to understand its life
cycle and evolutionary history,
its botany, and its role in
the vast biome for botany, and
its role in the vast biome for
which it had become emblematic.
We also need to look at the
chronology of its demise to
learn what we can about the
roots of this epidemic. The
pathways of our investigation
may take us in some unexpected
directions.
When the chestnut blight (Cryphonectria
parasitica, sometimes called
Endothia parasitica)
was first identified on American
chestnut in 1904 at the New
York Zoological Garden, it's
likely that the disease had
already been at work for as
much as a generation. This is
inferred because the spread
of the disease was very rapid
after 1904.
The first Japanese chestnuts
were imported to the United
States in 1876 for the nursery
trade. Japanese chestnuts (C.
crenata), which have very
large nuts, are the most blight
resistant of the main chestnut
species. Their Chinese cousins
(C. mollissima) share
some of this resistance. The
European species (C. sativa)
was susceptible, and was infected
by the blight in the 1950's
after its American cousins had
already collapsed, but surprisingly,
a hypovirulent (less potent)
strain of the fungus appeared
in Italy and spread through
European groves. After about
15 years of infection the European
chestnuts seemed to have recovered;
they continue to bear commercial
crops.
Not so lucky the American chestnut.
Soon after the blight was discovered
in the Bronx, infected trees
were found in southern New England
and New Jersey. The blight began
its slow, deadly march south
along the Appalachian chain.
A
Tree Nonpareil
Chestnuts were more than an
important tree in Appalachia
- they had been the ridgepole
of the economy. Chestnut lumber
was far and away the greatest
part of the economic value of
the hardwood forest. It was
used for everything from barns
to caskets. The trees provided
the nations's main source of
tannin for leather processing.
Animals, including large herds
of domestic hogs, fattened on
the nuts, and perhaps most socially
significant, the chestnut provided
a ready cash income to millions
of rural dwellers. In an era
when the daily wage averaged
$1.75, chestnuts sold for ten
cents a pound. A man working
the harvest could easily gather
100 pounds in a day, and could
put by a year's savings from
a few weeks work. [3] The subsequent
loss of the chestnut, simultaneous
in most places with Prohibition,
drove rural mountain dwellers
to "moonshining,"
converting their corn into mash
and thence to bootleg whiskey,
as the only way to derive a
cash income from the land and
to pay the taxes. Later tobacco
would join alcohol as a principal
replacement for the chestnut
in the region's cash economy.
About 1911, as it became obvious
that a catastrophe was in the
making, the federal government
began funding efforts to avert
the impending disaster. Plant
quarantine legislation was passed
in 1912. Fungicides were tried
unsuccessfully. Chemical treatment
proved ineffective. Attempts
were made to cut a wide "firebreak"
barrier to prevent the advance
of the disease, but the blight
jumped past it, spreading as
much as 50 miles a year. By
1938, most of the chestnuts
were dead.
In the early years of the 20th
century, scientific forestry
was in its infancy. Evolutionary
biology was still a relatively
new science, and ecology was
scarcely known. Although the
chestnut emergency stimulated
scientific research into the
etiology of the fungal disease,
and breeding work based on this
research appears promising,
a holistic view of the phenomenon
has yet to emerge. A crisis
and bottom-up action appears,
through these same tools of
analysis, to be random and chaotic.
Its true meaning may only be
understood by taking a systems
approach or top-down view.
Chestnut
Botany
Chestnut first appeared in North
America about 40 million years
ago. It is a member of the beech
family, Fagaceae, to which belong
also the oaks, all relatively
long-lived, crown-bearing nut
trees common to the forests
of Europe, North America, and
east Asia. These trees are all
"mast" bearers, that
is, they throw large crops of
seed every two to three years
rather than annually. Their
highly nutritious nuts are rich
in carbohydrates and less oily
that the walnuts and hickories,
to which they are more distantly
related. The mast provided seasonal
food for a huge number of birds
and mammals, as well as humans,
and the irregular pulsing of
the tree's reproductive cycle
was an adaptation to this heavy
seed predation, a strategy biologists
call "satiation."
A periodic dearth of mast suppresses
populations of the deer, turkey,
squirrels, pigeons, and others
who prey upon the tree's seeds.
This ensures that when abundance
returns a year or two later,
some of the billions of seeds
will survive the (much reduced)
onslaught of hungry seed predators.
Anatomy
of a Forest Giant
Among the chestnuts, the American
produces the smallest but the
sweetest nut, a food that was
highly prized by native Americans,
the European settlers in the
region, and by a plethora of
wildlife.
Within the 200 million acres
of its native range, American
chestnut dominated the forest.
At the time of its collapse
it was at least one in every
four trees throughout the eastern
U.S. Favoring north- and east-facing
cove slopes where it comprised
over half of the forest, it
often occurred in pure stands.
Dominance was supported by it
ability to persist shrub-like
in the undergrowth for many
years (the reason it has not
been eliminated biologically
from the forest), its habit
of rapid growth following disturbance,
and by the production of allelopathic
chemicals in its leaves and
bark. These substances, leachates
of which were constantly dripped
into the surrounding soils by
regular rains, suppressed the
seed germination and growth
of other trees such as white
pine and hemlock which might
otherwise have competed successfully
for the same niches chestnut
favored. [4] Great height assured
its ability to photosynthesize
and bear seed, while rot-resistant
wood allowed the tree to persist
in the constantly moist environments
of its native terrain.
The chestnut, unlike its cousins
the oaks and beeches, with which
it was often associated, is
a shallow-rooted tree. It achieved
its towering heights and great
spreads by the use of lightweight
wood and a massive reach of
lateral roots. It typically
grew on well-drained, sloping
soils, in moist microclimates
under high rainfall regimes,
all factors consistent with
its rooting habit.
So, we should ask: How did this
tree, which grew so fast and
bore copious crops of nutrient-rich
seeds, feed itself?
Like other deciduous species
in the Eastern North American
forest, chestnut dropped its
leaves each autumn to blanket
the soils at its roots, and
these droppings over millennia
built up deep humus-rich soils
which, like a battery, were
able to hold the vast quantities
of nutrient needed to feed the
trees. But what charged the
battery? Soils in the southern
Appalachians (where the chestnuts
reached their greatest glory),
despite present forest cover,
are heavily leached and nutrient-poor.
The trees still drop their leaves,
but the soil battery has been
run down. Some of this, to be
sure, is a historic consequence:
logging throughout the Appalachians
was ruthless and soil erosion
losses were immense. But we
have to see past this. Chestnuts
grew on slopes where soils were
always thinner and less fertile
than in the bottomlands. Rainfall
of 50-60 inches per year promotes
soil acidity which in turn ties
up some minerals, and together
with warm summer temperatures
stimulates rapid leaching of
the rest. Are we facing a paradox?
The heaviest logging and the
most destructive erosion occurred
after the chestnut blight began
to spread, in the 1920's. In
part this was an effect of the
blight, which encouraged landowners
to cut chestnuts for their wood
before, or shortly after infection.
With one of every four trees
removed from the forest, some
in pure stands, a shock wave
rolled over the mountains. In
the wake of this logging and
with the loss of the chestnut
gutting the local cash economy,
massive depopulation took place
throughout rural Appalachia.
Our question remains, however,
what was at the root of this
collapse, the end phases of
which were so grim? Human activity
without a doubt: The chestnuts
fell victim to foreign imports.
They were an early casualty
of global trade: a host of helpful,
noble, innocent natives felled
by a dastardly foreign villain.
That story played well to a
society grappling with endemic
racism, but it's rather too
simple. Something is missing.
Let's consider the heroic success
of the chestnut.
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The
Chestnut Ascendancy
Following the last glaciation
and southward retreat of the
hardwood forests, the chestnut
began to spread out of the southern
Appalachian coves where it had
taken refuge, back into the
Ohio Valley and New England.
Pollen records indicate that
it reached Connecticut and Massachusetts
in large numbers about 2500
years ago. [5] A parallel
but even more pronounced spike
in New England chestnut populations
appears to have followed on
the arrival of Europeans in
the area some four hundred years
ago, suggesting that disturbance
favors its spread.
We appear to be dealing with
an opportunistic and aggressive
tribal tree species that was
at the same time long-lived
and dependent on relatively
high levels of available soil
nutrient. It both suppressed
unrelated competitors in its
own niche by the use of allelopathic
chemicals, and outstripped the
growth of those close relatives,
oak and beech, which could tolerate
its chemical effusions. What
sustained it?
Plants that produce fruits are
always interested in attracting
bird or other animal seed dispersers
as part of their reproductive
strategies. The energetic investment
in fruit is paid back by the
manifold opportunities to reach
distant niches with one's offspring
delivered in a high-nutrient
packet of fertilizer. But chestnut
seems not to have adopted this
evolutionary approach; rather
it depended on the scatterbrained
habit of squirrels to plant
its seeds nearby and forget
where most of them went! Since
the tree was tolerant of understory
conditions and content to live
in pure stands, distant spread
of its progeny apparently wasn't
needed, while the advantages
of growth close by the protective
boughs and chemistry of the
tribe were considerable.
Most of the animals that fed
on chestnuts were seed predators:
deer, turkey, and the now extinct
passenger pigeon. While deer
populations at upwards of 10
million may now exceed historic
levels (because of the increase
of patchiness in the landscape
and the absence of large predators),
and turkey numbers are recovering
from a low of 30,000 a century
ago to nearly a million and
a half today, in sheer numbers,
in total biomass, and in the
rapidity of cycling of food
resources, these surviving creatures
were completely dwarfed by the
passenger pigeon. It is to the
saga of the pigeon's glory and
final days that we must turn
for clues to the nutrient base
of the chestnut.
A
Bird Made for Flight
There was never a sight in all
the world we humans have known
to match the splendor of the
passenger pigeon in its flights.
Vivid in their red, gold, and
purple plumage, with long tails
and streamlined bodies, they
were grace incarnate as they
sped by overhead in veritable
torrents of birds, wheeling
and turing, rising and diving
with a thunderous flapping of
their wings, as if the whole
were an avian embodiment of
the aurora borealis. Perhaps
the great herds of wildlife
moving over the Serengeti may
inspire a similar feeling of
awe.
Numbering, like the chestnut,
about four billion individuals
in the early 19th century, the
passenger pigeon may have been
the most successful social bird
ever to have lived. Completely
dominating the skies within
its range, it may have been
as much as 40% of the bird population
of the continent, the most numerous
higher animal species on earth
at the time. [6] Intensely gregarious,
it massed in numbers beyond
comprehension. J.J. Audubon
describes a flock that passed
him over Kentucky. He began
tallying groups as they passed
overhead but soon gave up as
the sky was darkened with their
vast number for more than three
days. Hundreds of millions of
birds in each mass may have
flown together. The largest
roosting of passenger pigeons
ever recorded was seen in Wisconsin
in 1871: it spread over 850
square miles, and was estimate
at 136 million, over 250 birds
per acre. This, however, was
after their numbers had already
begun to decline significantly.
The pigeons were adapted to
prime functions: they fed voraciously
and systematically, and they
flew like mad. Having effectively
escaped the limits of predation,
they drew strength in sheer
numbers and great speed, overwhelming
the ability of any predators
(save ultimately humans) to
seriously dent the size of the
colony. Audubon again reports
that birds taken in New York
had undigested grains of rice
in their crops, seed that could
only have been eaten fresh from
the fields in South Carolina
or Georgia. Since the power
of the bird's digestion is great
and complete passage of food
takes no more than 12 hours,
he concluded that they must
have exceeded a sustained speed
of 60 miles per hour in their
marathon flights.
With keen eyesight they could
survey the countryside at high
speed to assess the availability
of large food resources. After
locating a sufficiently rich
country the colony would roost
in dense forest, settling into
the upper branches at such densities
that large limbs regularly fell
crashing through the masses
of birds perched below, and
"many trees two feet in
diameter, I observed, were broken
off at no great distance above
the ground..."wrote the
master artist and naturalist.
On their departure the roosting
areas would resemble "very
much a section of country over
which has passed a violent hurricane,"
noted Col. David Crockett in
1835.
Once roosted, the colony would
range, en masse, up to 200 miles
a day in search of food, returning
at night to the woods. They
ate like the whirlwind, observers
commenting on the rolling wheel
of birds that would move through
an area. The colony would land
and the lead birds would move
systematically through the fields
or wood, eating seeds, nuts,
berries, earthworms, grasshoppers,
and even burrowing with their
beaks for tubers and legume
nodules. As the front exhausted
an area, birds in the rear would
rise up, swoop over the flock,
and settling to earth just ahead
of the colony's advance, take
their place on the feeding line.
This continued patiently throughout
the day or until predators menaced,
then the whole mass would take
wing and speed off to another
area. They continued harvesting
until the resources of
the whole region were depleted;
then they would depart to find
the next landscape of surplus.
In their migrations they never
took the same path twice, but
always sought territories rich
with food.
Undaunted by cold (they ranged
north to Hudson's Bay and to
the south end of Lake Winnipeg,
58 degrees and 62 degrees N.
latitude respectively), they
were recorded moving north in
early March while temperatures
hovered at -20 degrees F. Winters
were spent in the upland of
Louisiana, Mississippi, Alabama,
Georgia, and the Carolinas.
They reached the Atlantic only
sporadically, but inhabited
both flanks of the Appalachians
and ranged west of the Mississippi
River and south to the Texas
Hill country.
Long-lived (the last passenger
pigeon died in captivity at
29 years of age), the birds
bred in affectionate, talkative
pairs, nested clumsily, and
raised one or two squabs per
nesting, most typically one
male, the other female. The
nests, made hastily of coarse
twigs, were so poorly constructed
that often one of the two eggs
laid or the two squabs hatched
would fall to the ground inadvertently,
there to make a meal for some
eager animal. The breeding cycle
took a little less than a month
and was repeated several times
each season. Audubon estimates
their increase to be two to
four times their number per
year. Since the population had
probably peaked near the capacity
of the subcontinent to support
their profligacy, it can be
imagined that several billion
passenger year (at 10-12 oz
/ 280-335g each, some 10 to
the 9th power kilograms of protein)
were consumed by various organisms,
and that they converted an immense
amount of vegetable and insect
matter into meat and dung.
"...and their dung would
fall like hail." [7]
"The dung fell in spots
not unlike melting flakes of
snow."
"The dung lay several inches
deep covering the whole extent
of the roosting places."
They favored beechnuts, chestnuts,
and oaks, eating so avidly that
on swallowing a particularly
large acorn, a bird might be
seen to gasp for some time as
if choking. Undoubtedly they
preferred the smaller beech
and chestnut mast for its ease
of consumption. They harvested
not only fallen nuts but those
still on the tree, having perfected
a method of grasping the nuts
in the husks and flapping their
wings backwards to extract the
kernels.
What the observers imply, but
do not record, is the action
of the birds in concentrating
nutrients from the surrounding
territories onto the soils of
the larger forest tracts. For
the birds always sought out
large unbroken woodlands for
their roosts (so much so that
late 19th-century deforestation
together with commercial hunting
almost ensured the pigeons'
doom). No more perfect description
of a nutrient pump ideally matched
to the demands of the shallow-rooted
deep-forest dominating chestnut
could be conceived. The birds,
which began their nesting in
mid-May, would lay down a thick
mat of mineral-rich manure just
ahead of the chestnut's June-July
bloom, a delivery of trace elements
well-timed to support the chestnut's
profuse flowering, its white
blossoms giving the mountains
the appearance of freshly fallen
snow at mid-summer.
In addition, the devastation
wrought by the pigeons' roosting
would have been an advantage
for young chestnuts growing
understory, opening holes in
the canopy that probably allowed
the trees to consolidate their
hold on an area.
But the flocks Audubon had observed
in the 1830's began to diminish
after the Civil War. By the
1870's clearing of forests for
farmland accelerated their decline
as the telegraph and railroad
networks allowed commercial
hunters at last to compete with
the birds' prodigious speed.
Markets in teeming eastern cities
made wholesale slaughter financially
attractive and literally trainloads
of pigeons were shipped to the
cities. Huge volumes were fed
to hogs. Michigan recorded its
last large nesting in
1878, Oklahoma and Pennsylvania
in 1886. By 1890 the passenger
pigeon was functionally extinct,
though isolated birds were still
seen in the wild for another
ten years. The last wild pigeon
was shot about 1900. [8]
Though they had bred successfully
in captivity since the 1870's,
efforts to raise the pigeons
artificially failed when they
disappeared from the wild.
The first phase of the crime
was complete. "Martha,"
the last captive pigeon in the
Cincinnati Zoo, took with her
to eternity the heartbeat of
this remarkable race on September
1st, 1914.
The thesis that these two great
American extinctions may be
causally linked appears to have
received little attention. Popular
historians and ecologists of
every stripe list them in virtually
the same breath as landmark,
human-generated events, yet
the ornithologists seem to not
be communicating with the forest
biologists. Ecologists might
seem a likely group to have
given this notion a passing
glance. Surely a few have at
least entertained the thought.
A
Possible Test
This hypothesis, which, absent
one of its main components,
is not susceptible to ironclad
proof, could nevertheless be
tested by exploring in greater
detail than has been done heretofore,
the link between mineral availability
and blight infection in chestnut.
My brief researches turned up
some references to present-day
blight-free (though stunted)
populations of chestnut in association
with mineral tailings from a
zinc mine in Pennsylvania. If
zinc tailings (containing who
knows what, at undoubtedly hideous
levels of acidity) can keep
chestnut blight-free, what about
two or three inches a year of
bird manure?
Forest clearance has been widely
understood as contributing to
the demise of the pigeon, but
the bird's pre-eminence - let
me now call it a keystone species
- in cycling nutrients over
the eastern half of the continent
cannot be underestimated. Writers
have noted, in the context of
pigeon extinction, the "inexplicable"
shrinkage of the beech forests
since early colonial times,
but have made little of it.
I posit that the chestnuts (which
did indeed succumb to the blight
organism, truly imported from
the Orient)were rendered dramatically
more susceptible than they might
otherwise have been by the choking
off of a main nutrient flow
in the generation immediately
preceding 1904. Indeed, the
blight, probably present from
the 1870's onward, may have
been kept in check by the residual
effects of the great nutrient
pump. I suspect that European
chestnuts weathered the attack
of the blight and survived
because of agricultureal cycling
of nutrients in the orchards
by the sue of swine, a creature
whose manure is even higher
in zinc than that of poultry.
We must ask ourselves: Might
not more of the American chestnuts
have survived had the pigeons
still been roosting in them,
and had the trees not been mowed
down in a kind of "salvage-logging"
hysteria, which surely eliminated
any evidence of native genetic
resistance? These surface-feeding
trees required a powerful replenishment
of mineral nutrient for their
steady production of mast and
their rapid growth. In the high-rainfall
environments of their native
range, soils are readily leached
of these nutrients unless continuously
"topped up". The balance
is a delicate one.
A
Modern Parallel
Though no one cognizant of modern
ecological theory was able to
record the interactions of pigeons
with chestnut trees, I have
personally observed parallels
with other surface-feeding nut
trees.
Macadamia nuts were established
in Hawaii from about 1964 to
diversify an agriculture heavily
dependent on sugarcane. These
large nut plantations, managed
by the Big Five sugar companies
throughout the islands, were
treated to the full range of
conventional agro-technology:
chemicals and mechanical harvesting.
By the early nineties a mysterious
fungal organism had appeared
which caused many macadamia
trees to die suddenly, within
90 days of infection. I witnessed
in one orchard the harvesting
of nuts by mechanical vacuum
acton that sucked everything
of the orchard floor up to and
including stones the size of
golf balls. Simultaneous with
the pillage, a scientist on
the other side of the orchard
was explaining earnestly to
a group of tourist about the
grim fate of trees growing sick
with this mystery fungus. Since
the macadamia is a surface-feeding
rain forest species, it should
have been no surprise that 30
years of abuse to the roots
of these trees, even on rich
volcanic soils, would result
in nutrient depletion, and weakening,
for which the mystery fungus
was only the cleanup crew.
Restoration of the chestnut
proceeds and I await it as eagerly
as any, but the eventual re-establishment
of chestnut groves would be
greatly supported by the incorporation
of an element of rapid nutrient
cycling such as the pigeons
once supplied.
Our confounding by the germ
theory of disease and a century
of phony medicine has crippled
our civilization's ability to
understand biological phenomena
holistically, especially in
the arena of death. [9] The
same focus on actors and objects
rather than processes and energies
has crippled our political understanding
as well. But let me conclude
with a brief consideration of
the concept of key species.
A
Keystone of the Continent's
Arch
I believe that the passenger
pigeon was a key nutrient cycler
that maintained forest health
on a sub-continental scale throughout
the eastern forest biome. By
the nature of its scale it could
have but few parallels. Two
others that come to mind
immediately are the bison, which
numbering in excess of 50 millions
maintained the tall-and short-grass
prairies over a million square
miles of the mid-continent -
and which were also ecologically
extinguished in the late 19th
century; and secondly, the salmon,
whose final days we may be tragically
fated to mark soon. These anadromous
(ocean-living, river-spawning)
fish translocated huge quantities
of marine minerals and protein
to the headwaters of western
rivers where they form a key
link in the food web, supplying,
with the help of top carnivore
bear and birds of prey, phosphorus,
calcium, and trace minerals
of inestimable value to inland
ecosystems. [10] These minerals
moved not in the salmon's feces,
as did the nutrients harvested
by the bison and the passenger
pigeon, but as their bodies,
which are sacrificed annually
by the millions of pounds.
Of course the bison and the
pigeon all fed large numbers
of carnivores and small consumers.
Nutrient flows from the pigeon
may have reached 10 billion
kilograms / year or more (concentrated
on the forests); from the bison
herds, two or three times as
much, though more uniformly
spread across the grasslands.
In aggregate these volumes approach
the scale of modern commercial
fertilizer use (much of which
is wasted anyway). Salon harvest
(over a smaller though still
significant territory) may have
reached approximately 500 million
pounds annually in Washington,
Oregon, California and Idaho;
we can only guess what prehistoric
quantities were involved, to
say nothing of the Canadian
and Alaskan streams. [11]
Toby Hemenway has written in
the magazine (PcA #48) of the
profound role played by beavers
in shaping North American river
valleys. To encompass the full
suite of ecological functions
now derelict (not merely species
extinct), we must look beyond
the beaver, the pigeon, the
bison, and the salmon, to see
the key role of elephants (gone
a mere 10,000 years) in maintaining
the nearly vanished American
savannas of the southern plains,
and of camels (more distantly
removed) in cycling nutrient
through the deserts of the Southwest.
We are looking out at a landscape
bereft of its most dramatic
living forces. If we are seriously
interested in restoring North
American ecosystems, we must
at least admit the abundance
that once was here and that
humans have destroyed, before
we can hope to reclaim it. We
might also entertain, as ecologist
Paul Martin and others have
proposed, the return of a few
elephants. [12] It might
give the California condor (our
top-order avian scavenger, which
once ranged to New England)
an invitation to move east again.
Ecologists argue over the meaning
of the term keystone species.
Strict constructionists prefer
the definition they attribute
to R.T. Paine, a biologist who
coined the term in 1966, which
insists that keystone species
are predators whose selective
predation helps to maintain
greater diversity at lower trophic
levels (that is, among smaller
prey organisms). [13] The other
school of thought holds that
keystone functions can be played
by many actors on the ecological
stage: prey species, habitat
modifiers, predators, and more.
I prefer the latter view, as
it invites free play of the
imagination; we are in a situation
where the scientific method
alone will not save us. Great
engagement by the public in
scientific inquiry is desperately
needed.
At the level of events and organisms,
ecological systems are inherently
chaotic. To understand the dynamics
of North American ecosystems
we must lift our view. We can't
afford to neglect either history
or the system's fundamental
organizing processes. Upstream,
upwind, and antecedent factors
are frequently decisive. Where
once the surplus energies of
the continent were channeled
through animal bodies, great
storages that have been squandered,
today they are harnessed to
human constructs, the greatest
of which are our cities. And
just as we have seen the collapse
of the largest-order populations
of the crucial birds, ruminants,
trees, and fish due to sporadic
action based on the bottom-up
fragmented, or strictly social
thinking, we are likely seeing
the incipient collapse of our
largest-order settlements from
the same kinds of action; this
time I fear, from a very different
kind of thinking. [14, 15]
Camels, elephants, pigeons,
bison, and salmon. These are
the keystones. Now, where are
the cops?
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References
1.
American Chestnut Foundation.
www.acf.org
2. American Chestnut Cooperators
Foundation. www.accf-online.org
3. Judy C. Treadwell, Mar. 1996
NC Natural
4. D.B. Vandermasta, D.H. Van
Lear, B.D. Clinton. "American
chestnut as an allelopath in
southern Appalachians",
in Forest Ecology and Management
(2002) pp. 165, 173-181.
www.elesvier.com/locate/foreco.
5. F.L. Paillet. "Chestnut:
history & ecology of a transformed
species: in Journal of Biogeography,
29, 1517-1530
6. Chipper Woods Bird Observatory.
www.cwbo.org.
7. Illinois Natural History
Survey Reports, May-June '98.
www.inhs.uiuc.edu
8. David E. Blockstein, "Passenger
Pigeons, Lyme Disease, and Us:
the unintended consequences
of the death of a species."
www.ncseonline.org/Directory/Staff/DBlockstein/birding_Aug_01.pdf
9. Adeha Feustel, "Bacteria:
Pathogens or Agents of Decay,"
in Permaculture Activist
45, Feb. 2000 10. Associated
Press, "Salmon are Natural
Recyclers." March,
2000
11. Brock Dolman, personal communication,
October, 2000
12. Connie Barlow, Ghosts
of Evolution. 2000
13. R.D.Davic, 2000. "Ecological
dominants vs. keystone species:
A call for reason."
Conservation Ecology 4(1):
r2. www.consecol.org/vol4/iss1/resp2
14.David Holmgren, Permaculture:
Principles and Pathways Beyond
Sustainability. 2002
15. Mike Davis, Dead Cities.
2001
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