How adaptive species became “invasive”
From ANIMAL PEOPLE, October 2007:
How adaptive species became “invasive”
Commentary by Merritt Clifton
“Exotic species,” “alien species,” and “invasive species”
are semi-synonymous terms which to most people may seem
Each is a metaphor for species not indigenous to their
habitat: non-native species, to introduce yet another term, less
rich in connotation.
Yet obscure as the distinctions among “exotic,” “alien,”
and “invasive” species may be, the terms are different enough to
have inspired environmental advocacy groups and government agencies
to spend millions of dollars in recent years to bring first “alien”
and then “invasive” into vogue.
Behind the linguistic politics is the belief that terminology
tends to shape attitudes. Thus, at about the same time that the
Natural Resources Defense Council began banging the drums about
“invasive” species, In Defense of Animals began to push use of the
term “guardian” rather than “owner” to describe a person who keeps a
However, while In Defense of Animals sought from the
beginning of the “guardian” campaign to change the language of laws,
the NRDC and others pushing alarm about “invasive” species merely
introduced their preferred terminology into public discourse. The
idea was to increase support for existing policies and programs
against non-native species, not to turn government in a different
direction. Indifferent and often even favorably disposed toward
“exotic” species, the public was believed likely to become more
concerned about “alien” species, and most likely to view “invasive”
species as a threat.
What’s in a name?
Dave Poulson, associate director of the Knight Center for
Environmental Journalism at Michigan State University, maintains an
online glossary of environmental terms. A careful lexicographer,
Poulson recently asked fellow members of the Society of Environmental
Journalists to help him distinguish the differing shades of meaning
among “exotic species,” “alien species,” and “invasive species,”
as used in news coverage.
Doug O’Harra of Far North Science, in Anchorage, Alaska,
offered distinctive definitions which might not withstand all
critical scrutiny, but were accepted by the discussion participants
as accurately reflecting most contemporary newsroom use.
An “exotic species,” O’Harra pronounced, is any species
living somewhere other than where it originated.
An “alien species,” O’Harra opined, is an exotic species
which was deliberately introduced to non-native habitat.
Neither exotic nor alien species “necessarily threaten the
local ecology,” O’Harra stipulated, but an “invasive species” in
his opinion “threatens the ecology of a local habitat by
out-competing or killing off native species–usually because the
native species lack defense mechanisms, “or because the
alien/invasive species no longer faces the predators or parasites
that held it in balance in the species’ original habitat.”
This is more-or-less what is usually taught in biology
classes, nature center visitor lectures, and wildlife
documentaries, but as ANIMAL PEOPLE pointed out, O’Harra’s summary
misses a key component of the process by which “exotic” or “alien”
species become allegedly “invasive.”
Typically, the ecology of the habitat has already been
transformed by climate change, cultivation, deforestation, drought,
volcanic eruption, or other events that take away the survival
advantages evolved by the native species through natural selection.
Whatever the native species came to do, that helped them in the
habitat of long ago, is no longer advantageous.
For example, shallow-burrowing native marsupials in
Australia lost much of their habitat to the introduction of sheep.
The sheep compacted the soil, ate the native plants, monopolized the
water, and were attended by bored shepherds who often amused
themselves by killing wildlife. The brushy dry forests of
pre-settlement times, burned to make pasture, gave way to desert.
Eurasian rabbits, who evolved with sheep, were enabled to
take over huge swaths of habitat, along with rabbit predators
including feral cats and foxes. Each moved into habitat niches which
had been made more favorable to them than to the extirpated
Thylacenes, or “tasmanian tigers,” also called ‘Tasmanian
wolves,” evolved to hunt marsupials in the dry forest. They crashed
toward extinction, and probably would have drastically declined
anyway, even if they had not been persecuted as suspected sheep
predators, because their habitat was radically altered and their
prey base was reduced. Thylacenes had persisted for about 8,000
years in competition with dingoes, who arrived with the first humans
in Australia, but the coming of sheep irrevocably tipped the
balance. Dingo ancestors had hunted rabbits–and sheep–in Asia.
They rapidly made the transition back to a rabbit-based diet, eating
sheep too when they could, and took over the habitat that thylacenes
could no longer hold.
When the adaptive success of “invasive species” to altered
habitat is understood in context, the insidious implications of the
term “invasive” become much more visible.
The history of the phrase “invasive species” is illustrative
of a linguistic parallel to the evolutionary process of how species
become “invasive,” demonstrating how a misguided belief can wreak
havoc when the cultural climate favors it, no matter how wrong it is.
“Invasive species” is actually of surprisingly recent origin
in common use, and despite years of deliberate effort to introduce
it, it only gained currency when the U.S. “cultural ecology” changed
abruptly in 2001.
Tracing the rise of the “invasive species” issue, ANIMAL
PEOPLE ran keyword searches of 1,428 U.S. newspapers indexed
1976-2006 at <www.NewsLib-rary.com>. We proportionally weighted the
findings to compensate for the rising frequency with which newspaper
content was filed electronically during the 30-year sampling.
Before 2002, the relatively neutral term “exotic species”
was the most commonly used collective term for non-native animals and
plants. No other term was even commonly used until 1999. The word
“exotic” is most often associated with “different,” “unusual,” or
even “erotic.” The positive associations of “exotic” long frustrated
ecological nativists, whose environmental philosophy evolved in the
19th century parallel to political nativism.
The basic idea behind both strains of nativism is that
whatever existed in a particular place at a specific time chosen by
the power-holders belongs there, while new arrivals are a threat.
Both strains of nativism have waxed and waned repeatedly in
influence, tending to gain strength whenever and wherever the
dominant culture is challenged by immigration.
For example, California in the 1930s could not legally bar
Dustbowl refugees from entering the state, but it could and did set
up checkpoints at the state borders to minutely inspect immigrants
lest they carry produce that might harbor insect pests.
Ecological nativists sought mostly unsuccessfully until
recent years to rally support for eradicating popular animals whom
they perceived as threats to their own favored species, and often
debatably termed “non-native” as a pretext for extermination.
Time and again, nativists were rebuffed–for example, in
seeking to kill mute swans to expand trumpeter swan habitat,
cutthroat trout blamed for depleting native trout in Lake
Yellowstone, and mountain goats who were accused of eating rare
alpine flowers in Olympic National Park.
Nativist purges of hooved species from the Channel Islands
and of feral cats from many locations were waged mostly against
public opinion, and were often possible only when privately funded
organizations such as The Nature Conservancy bought the land to be
purged, then did the killing before turning the land over to the
U.S. or state governments.
The public has generally supported campaigns against the
likes of the lake weed Eurasian watermilfoil, lampreys, zebra
mussels, and gypsy moths, but even these efforts have been stalled
at times by concern rising ever since Rachel Carson published Silent
Spring in 1963 that the chemicals used to kill so-called pests may be
more harmful, in many instances, than the target animals and plants.
For decades wildlife management publications and conferences
have openly and often discussed ways of persuading the public to
share nativist antipathy toward non-native species. Dire warnings
that popular non-native species might displace seldom-seen native
animals and plants have had little or no effect.
Ecological nativists eventually began trying to introduce the
term “alien species” in place of “exotic species.” This also failed
to kindle. For the first decade or more that “alien species”
appeared in print, it was associated mainly with science fiction and
teenage behavior, rather than ecology and biology.
Only in 1993 did “alien species” gain even marginal
visibility, and the term has never been used by U.S. newspapers at
more than about a third of the frequency of “exotic species.” 1993
also brought an almost fourfold increase in coverage of “illegal
aliens,” and an almost fivefold rise in coverage of “illegal
Indicative of which non-natives were of most public concern,
“illegal aliens” were mentioned seven times more often in 1993 than
“exotic species” and “alien species” combined. “Illegal immigrants”
were mentioned three and a half times more often.
The impact of 9/11
Discussion of “invasive species,” not even mentioned in
print before 1988, likewise rose in 1993, reached statistically
significant visibility in 1995, and achieved a virtual dead heat
with “exotic species” by 2001, coincidental with the first external
attack on Americans on American soil since Pearl Harbor, 60 years
Attention to “invasive species” then nearly doubled in one
year, tripled in two years, and by 2006 occurred at four times the
frequency of “exotic species.”
How that happened appears to have little to do with
increasing recognition of an actual problem, as “exotic species” and
“alien species” were discussed no more often than before. Yet
mentions of “illegal aliens” and “illegal immigrants” surged to
five-year highs in 2001, and rose after 2002. Discussion of
“illegal aliens” in 2006 soared to the highest point in a decade,
while discussion of “illegal immigrants” nearly doubled, far
surpassing the 1994 previous peak.
What this means to animals and public policy appears in the
funding allocated by Congress to support the official U.S. government
extermination agency, USDA Wildlife Services–which originally
focused entirely on killing native predators of introduced livestock.
Ancestrally part of the U.S. Geological Survey, funded to extirpate
wolves from the continental U.S. in the early 20th century, this
agency was moved to the U.S. Fish & Wildlife Service, retitled
Animal Damage Control, and assigned to exterminate coyotes in 1930.
Under the Fish & Wildlife Service, coyotes were massacred in
record numbers year after year, yet spread from the southeastern
quadrant of the U.S. to all 48 states plus Alaska. Amid indications
that the Fish & Wildlife Service had become uncomfortable with the
predator control mission, and under pressure from western ranchers
to kill even more coyotes, former U.S. President Ronald Reagan moved
Animal Damage Control to the USDA in 1986. The USDA renamed the
agency Wildlife Services to try to shake the murderous reputation
established by Animal Damage Control, but without success.
Wildlife Services, with a 1998 budget of $28.7 million, was
nearly abolished in June 1998 by the House of Representatives. A
motion by Peter DeFazio (D-Oregon) that would have in effect
disbanded Wildlife Services actually cleared the House on first
reading, strongly supported by pro-animal organizations and some
environmental groups, who recognized the mandate of exterminating
predators as inherently anti-ecological, and especially mistrusted
the use of chemical sprays and poisons. The DeFazio motion,
unfortunately, was defeated on a second vote after frantic rancher
Ecological nativists then joined with ranchers in ratcheting
up alarm about “invasive species,” managing to nearly triple
coverage during the next year.
At instigation of then-U.S. Vice President Albert Gore,
then-U.S. President Bill Clinton in February 1999 reinforced and
enormously expanded the role of Wildlife Services by creating the
Invasive Species Council, whose continuing existence was
reauthorized by the so-called REPAIR Act passed by the House of
Representatives on October 23, 2007. The main stated goal of the
Invasive Species Council is to eradicate such non-native “nuisance
species” as kudzu weed, gypsy moths, zebra mussels, and fire
ants-by hiring Wildlife Services.
In the fine print, however, the anti-“invasive species”
mandate extends to practically any species hated by anyone
The strategy of preserving Wildlife Services by aligning it
with the nativist philosophies of many major environmental groups
succeeded bigtime. Under current U.S. President George W. Bush, the
USDA Wildlife Services budget has expanded to $78 million in fiscal
2007, nearly three times the 1998 budget. Since the Bush
administration in 2004 pushed through Congress an amendment to the
1918 Migratory Bird Treaty Act that stripped more than 100 bird
species of protection, Wildlife Services can kill animals with less
restraint than at any time since the 1973 passage of the Endangered
And there is no longer much opposition to the killing from
most of the environmental community. Many of the biggest
environmental organizations are now preoccupied with human
immigration issues, ranging from the effects of increased human
population to the question of how fencing the U.S. border with Mexico
may affect jaguars and pronghorn. The Gray Ranch, a Nature
Conservancy property in southern New Mexico, includes routes often
used by illegal immigrants. The Sierra Club has been deeply and
bitterly split by debate over member resolutions, so far not
approved, opposing immigration.
Ecological issues associated with human immigration are real
and must be addressed, not least because they are probably only
beginning. The most recent projections of the effects of global
warming suggest that huge movements of humanity are inevitable, as
result of droughts, floods, fires, rising seas, and possible
famines. The human movements will be only one symptom of
environmental changes that are already starkly evident in the
receding snowcaps on most high mountain ranges, worldwide. Species
evolve in response to habitat, not points identified by a Global
Positioning System, and the habitat that many North American species
prefer is already several hundred miles north of where it was just a
few decades ago.
Climate change and ecological transformation are inevitable,
even if the global warming trend is reversed well short of the
worst-case scenarios. In view of that circumstance, rigidly
defining “native” v.s. “non-native” species is an exercise in
futility, no matter what names are used for them. Nature, not
human intervention, will decide where animals and plants “belong”
Bio-xenophobia looks more and more like just another symptom
of plain old-fashioned xenophobia: the fear of anything exotic or
alien, invasive or not.