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David I. Theodoropoulos, Las Sombras Biological Preserve, Box 337, La Honda, CA 94020-0337 USA
(408) 236-3728


The "Invasive Species" Crisis: Is it real?
Prediction: Is it possible?
Unanswered Questions
Literature Cited

As a conservation biologist, I am very concerned by the NISC plans to institute a "comprehensive screening system" to be applied to all organisms introduced into the U.S., as well as "applying similar principles...to species currently in the trade." The institution of such a sweeping, intrusive, expensive, and unprecedented policy must be fully justified on the basis of current scientific knowledge, it must be fully justified economically, and it must be fully justified ecologically. Such a policy must be practical and realistic - it must actually be possible to predict harm or invasiveness of the species screened. I am deeply disturbed that such a policy would be considered, and a timetable for its complete implementation imposed, entirely in the absence of effective screening methodologies, or even a theoretical basis for developing such methodologies. Such a policy, which will profoundly affect all sectors of our society, must not be hastily imposed. The public, the research community, landowners, farmers, and the business community must all be fully and openly informed of this policy and the full ramifications of its imposition. Adequate time must be allowed for full public discussion. I have found the research community in particular to be almost completely unaware of this proposed policy and the negative effects it will have on many areas of research and many important conservation strategies. The NISC has engaged in a pattern of biased reportage of the facts surrounding anthropogenically-dispersed species and has systematically excluded scientific evidence contrary to their agenda (see below for citations. The breathless hysteria-mongering of the government's websites and press releases, and the systematic exclusion of opposing views cannot be justified. The NISC appears to have selectively publicized its efforts to groups already convinced of the need for such a sweeping intrusion. The NISC has engaged in what appears to be a pattern of delays which could be construed as intended to prevent adequate time for the public and research communities to fully evaluate the ramifications of such a policy. For example, the failure to publish the Draft Management Plan until the morning of the first "listening session" for public comment is unconscionable. The failure of the NISC to provide a website (other than an "under construction" placeholder) until after public "listening sessions" had begun also demonstrates their failure to adequately inform the public and allow time for evaluation of their plans, or suggests a deliberate attempt at obscuring the issues. The NISC Invasive Species Committee Members are a stacked deck, filled with persons with a vested interest in promoting a one-sided view of anthropogenically-dispersed species. The presence of an herbicide manufacturer representative (Mr. Jackson), industry representatives and academics with careers promoting "invader" fears is very troubling in light of the absence of representatives from associations of botanic gardens, zoological gardens, germplasm banks and others whose research and conservation work requires that the movement of species be free of unnecessary roadblocks. There is a notable absence of skeptical voices on the Committee. The NISC has apparently engaged in a pattern of deliberately misleading and confusing the public concerning the comprehensive screening system. For example, the letter from Executive Director Lori Williams to concerned citizens appears to me to clearly display an intent to mislead by making sweeping denials couched with enough vague qualifiers to perhaps be technically true, but which do not address the issue at hand.


Purple loosestrife (Lythrum salicaria) is claimed to be "an aggressive invader, it has displaced native vegetation and destroyed waterfowl habitat by forming dense, nearly monotypic stands" (Hight 1993). The National Invasive Species Council (NISC) places it among their top invaders. However, Anderson (1995) reviewed 34 papers on loosestrife and found records of 29 native species of wildlife using the plant, and many records of native species outcompeting it. In 41 plots in Ontario, no significant difference in vascular plant species richness was found, regardless of the presence of purple loosestrife, no differences in number of introduced species, nor was species richness affected by increasing percent cover of loosestrife. A number of native species were more likely to grow in plots containing purple loosestrife (Treberg & Husband 1999). Hager and McCoy "traced the history of purple loosestrife and its control in North America and found little scientific evidence consistent with the hypothesis that [it] has deleterious effects... Loosestrife was initially assumed to be a problem without actually determining whether this was the case... there is currently no scientific justification for the control of loosestrife..." (Hager & McCoy 1998). Yet loosestrife is still touted as an "invader" - Pimental et al (2000) give it top billing and claim $45 million in control and loss costs in the U. S. alone, and the NISC features it prominently on their website. Although it has been five years since Anderson's paper, and Hager and McCoy's and Treberg's papers are a couple of years old, the NISC has ignored their work -- is this dishonesty on the part of the NISC, or mere incompetence?

Malakoff (1999) claims saltcedar (Tamarix spp.) is an "ecological menace", and has "proved disastrous for many native species, crowding out the cottonwood trees and willows... Fears that saltcedar will drive more species to the edge have put the plant at the top of ecologists' hit lists." The OTA (U.S. Congress 1993) claims it is one of the nation's worst weeds and that it increases flooding and sedimentation, alters hydrology, and crowds out native plants. However, as early as 1980, Everitt (1980) pointed out that it is a "slow starter that does not compete well" and that "there is as yet no convincing evidence, although the literature is rampant with charges that saltcedar is a potential flood hazard'.... [It] occupied land made available by the plow, the bulldozer, and the shrinking of a channel depleted of flow by upstream water development. Changes in both the physical environment and the native vegetation were well underway by the time tamarisk became widespread. There is no evidence that it actively displaced native species nor that it played an active role in changing the hydraulic or morphological properties of the river." (Everitt 1998) [emphasis mine]. Also, saltcedar stands are artificially "maintained in a youthful thicket' stage by burning, chemical treatment, or mechanical disturbance, so that seral species are not able to occupy..." In a study of the free-flowing middle San Pedro River "mean values for 22 of 30 soil, geomorphology, and vegetation structure traits did not differ significantly between saltcedar and Fremont cottonwood stands. Twenty-six of the 30 traits had similar patterns of change over time... Saltcedar was functionally equivalent to Fremont cottonwood for about half of the traits construed as indicators of riparian ecosystem function. Also in contrast to the working paradigm, saltcedar appeared to enhance the maintenance of floristic biodiversity. Understory herbaceous cover and species richness were significantly greater than cottonwood stands... Stem densities of velvet mesquite (Prosopis velutina) and other woody successional species did not differ between saltcedar and cottonwood stands." (Stromberg 1998). Saltcedar is said to salinize the soil, yet under natural flooding regimes, the salty leaf litter "is frequently flushed downstream" (Everitt 1998), and Anderson (1996) has pointed out that anthropogenic salinization frequently precedes saltcedar establishment, preventing the germination of native species. It is called a "water guzzler," lowering water tables and drying springs, yet its evapotranspiration rate does not exceed native cottonwood. The U.S. Fish and Wildlife Service originally cite saltcedar as a cause of decline of the endangered southwestern willow flycatcher, yet 90% of Arizona's 150 flycatcher pairs nest in it (Malakoff 1999). The extermination of beavers (Castor canadensis) in the Southwest has altered hydrology, water quality and species composition, and their reintroduction increased riparian habitat and raised water levels have killed saltcedar in some areas (Albert & Trimble 2000). It has declined in the middle basin of the San Pedro due to recent environmental changes, including flooding, greater stream flow and cattle exclusion. Clearly, this organism is anthropogenic, a disturbance indicator, and not a cause for alarm. Twenty years ago, Everitt (1980) eloquently stated that "An apparently widely held belief is the 'devil theory'... widespread use of the terms 'aggressive colonizer' and 'invader'... implies at least a subconscious belief that the species is somehow capable of actively destroying preexisting plant communities... It is doubtful whether many ecologists can be found who espouse such an anthropomorphic explanation of plant behavior..." and he made "A plea for research." Sound advice indeed.

Eucalyptus has been called "the tree Californians love to hate." It is said to invade and destroy diverse native ecosystems by allelopathically suppressing understory and being of no value to native wildlife, as well as being an explosive fire-hazard. However, in reviewing research on the tree, Stein & Moxley (1992) note that California eucalyptus forests are "far from faunal deserts'... a number of species not found [in surrounding chaparral] were found in eucalyptus plantings at Montana de Oro State Park. These species included monarch butterfly, Anna's hummingbird, golden-crowned kinglet, starling, dark- eyed junco, great horned owl, and yellow-bellied sapsucker.... Forty-seven species of native birds were known to use eucalyptus in the Golden Gate National Recreation Area..." Eucalyptus understory in the GGNRA included 36 species, cover and abundance was correlated with moisture availability not tree density, and eucalyptus created a microclimate which "permits some native herbs, shrubs and trees to grow on sites that did not support these species before..." (Stein & Moxley 1992). I have found many sites on which native species cover, richness and diversity increase as one approaches a eucalyptus trunk (Theodoropoulos, unpublished field notes). A study found that 3 cm of eucalyptus mulch did not inhibit germination and establishment of 5 of 6 species of native plants (Yamada & Sandoval 2000). Eucalyptus do not spread at most California sites, and this is mostly unquantified, and site-specific (Stein & Moxley 1992). Eucalyptus groves are the preferred sites for monarch butterfly overwintering congregations in California - 17 of the most prominent 25 sites are in eucalyptus trees (another 4 sites are in other non- natives) (Marriott 1997). Eucalyptus were blamed for spreading the disastrous October 1991 Oakland hills fire, yet many homes were actually shielded from burning debris by the trees (Anonymous firefighter, personal communication), and often eucalyptus were untouched while neighboring houses were incinerated (Larson 1991). In spite of the lack of credible justification, hundreds or thousands of hectares of eucalyptus are being removed as "invaders", including controversial projects such as at Angel Island, which destroyed valuable cultural, historical and scenic resources.

Hydrilla (Hydrilla verticillata) is called one of Florida's "most aggressive alien plant species." Yet its presence is linked to increased nutrient loading of waters from agricultural and urban runoff. The plant increases benthic and epiphytic invertebrate populations and species density, provides a haven for juvenile fish and is important for maintaining a high yield of fisheries. It is heavily used by waterfowl, is an important food for ducks, coots and moorhens, and hydrilla supports the highest avian species diversity in Florida (Schmitz et al. 1993). Fish density, biomass, species diversity and composition were compared between H. verticillata and the natives Panicum hemitomon and Potamogeton illinoiensis in Lake Okeechobee, Florida. Hydrilla had the highest fish density and biomass, with 3.27 times the density, and 2.5 times the biomass as the native Panicum, and 6.3 times the density and 5 times the biomass as the native Potamogeton, and species density did not vary significantly between the types (Chick & McIvor 1994).

Fish introductions are said to destroy native fish faunas. However, like other groups, they are primarily disturbance indicators. In Puerto Rican streams, the presence of dams was the determining factor in exotic fish presence, with natives abundant in undammed and below-dam streams, and exotics dominating above-dam (Holmquist & Schmidt 1998). In sampling a California reservoir, of 24 fish species, 5 native species accounted for 77% of catches (Vondracek et al. 1989). "The native non-game fishes have maintained large populations in the reservoir despite continued introductions of non-native species." The "catastrophic" introduction of Nile perch (Laetes nilotica) is said to have "virtually wiped out an entire icthyofauna of several hundred endemic haplochromine species" in Lake Victoria (Coblentz 1990). However, there has been a recent resurgence of indigenous species. Many species thought to have disappeared survive in refugia, and other indigenous species persist and are abundant in open waters. Haplochromines have increased in Lake Kyoga with the spread of water hyacinth, which may provide cover (Chapman et al. 1996). Although introduced fish are often blamed for amphibian declines, in Yosemite, California, frog populations persisted in high numbers for decades after repeated yearly large scale introductions, and they also have disappeared from fish-free sites (Drost & Fellers 1996). "Are fish introductions a threat?... Because of the paucity of information, the effects of introductions on endemic species remain controversial." (Crivelli 1995).

The spread of introduced fire ants (Solenopsis invicta) is said to "obliterate most native ants, plus a good many spiders, worms, and other invertebrates" (Devine 1998), as well as eliminate small mammals and ground-nesting birds. Again, they are primarily disturbance-dependent (Tschinkel 1993) (Fig.4), and spread was aided by the Mirex fire-ant extermination program, which destroyed native ant species. Fire ants were suggested as being linked to decline of overwintering birds, loggerhead shrikes (Lanius ludovicianus) in particular (Lymn & Temple 1991), but Yosef & Lohrer (1995) found no association between fire ant density and shrike reproductive performance and found other causes for the decline, including ant-control pesticides. "In no case have we observed fire ants to attack or kill eggs, nestlings or adult shrikes." Declining northern bobwhite (Colinus virginianus) populations have been blamed on fire ants, but experimental work (Brennan 1991, 1993) found "that fire ants have no influence on quail production ...bobwhite density is 2 birds per ha, and the density of active fire ant mounds is 200 per ha... Still the fire ant myth persists, and must be eliminated through education."

Called "a destroyer of forests... rampaging across millions of acres in summertime blitzkriegs..." (Devine 1998), the gypsy moth (Lymantria dispar) actually causes selective mortality in eastern hardwood forests - weaker trees succumb, and outbreaks are correlated with disturbance and urbanization (Dahlsten 1986). Subsequent outbreaks are less damaging. Also, "thirty eight species of birds and small mammals" eat the moth (Sharples 1983).

Chinese tallow tree (Sapium sebiferum) is called a "pernicious pest" in the South, where it is "one of the most destructive invasive plants in the U.S." (Devine 1998). Young stands are nearly monospecific, but within 20 years native riparian trees and shrubs were present and increase with stand age. With time, a new type of woodland is expected (Bruce et al. 1995).

Clearly, these few examples demonstrate that the simplistic view of an "invasive species crisis" trumpeted by the NISC is not scientifically justifiable. They also demonstrate that the NISC has either failed to do the most basic library research on the subject, or has engaged in deliberate deception of the American people by a selective and one-sided presentation of evidence. If there are any other possibilities than incompetence or dishonesty, please enlighten us.


PREDICTION: Is it possible?
"In dealing with invasions, ecologists are... attempting to predict the fate of diverse, often little-known organisms launched at diverse, complex, usually barely studied environments. And they are attempting to do so even though natural systems are so complex that it is usually very difficult to predict population size changes in well-studied organisms in well-studied environments." (Ehrlich 1986)

Attempts to predict invasion face the immediate limitation of the rudimentary state of our knowledge of the environment. We have named perhaps one-tenth of the earth's species, and our knowledge of the ecology of the majority of these species is non-existent. Our knowledge of the capacities of individual species and the composition and properties of communities and ecosystems is so limited and fragmentary that prediction is effectively impossible. In spite of over 50 years of scientific study of wildlife-habitat relationships we are still unable to accurately model or predict the abundance and distribution of well-studied wildlife (Morrison 1991). Concerning predicting species ranges in response to climate change, Lawton (1998) states that the "overwhelming evidence" from history is that species "respond idiosyncratically" to change, existing interactions uncouple, and "totally new interactions" form. "Even though virtually all the species still survive, there are combinations of species (communities) from these earlier times that have no modern equivalents, and many modern communities that have no ancestors in the sub-fossil record." Even well-recognized modern communities vary widely in species composition. Each site carries its own unique set of environmental factors, which may vary widely over small temporal and spatial scales. Single-year or regionally-restricted studies will lead to fallacious conclusions. Resident species may vary widely in habitats occupied, and interactions with other species change seasonally and among years. Species interactions vary continuously over wide ranges with changing conditions and stochastic events, and individual organisms are continuously confronted with novel conditions. Changing interactions with other species play key roles in determining the distribution and abundance of organisms, and metapopulation structure and source-sink dynamics change with changes in range (Lawton 1998). Each new species, whether native or exotic, entering an area where it is absent brings with it a new set of variables. "No prediction that fails to include all the variables in the case to be predicted can hope to succeed, yet each new invader introduces its own novel set of characters." (Williamson 1999). New properties may arise, and new interactions are unknowable. Exotics in New Zealand did not inhabit the same realized niche as in their English homeland, but were pre-adapted to different niches (Wilson et al. 1988). Such unpredictable emergent phenomena are unknowable. "Predicting the ecological behavior of a species in a new environment may be effectively impossible." (Williamson 1999). For example, the mild behavior of the zebra mussel in Europe, where it "invaded" long before it reached North America, is quite different from its behavior here.

Intrinsic properties of individual species are not predictive. Berman et al. (1992) studied three species of introduced marine invertebrates and found "that ecological similarity among species is not an accurate criterion to predict either the mechanism of invasion or the means of persistence." Analyzing introduced birds in New Zealand, Duncan (1997) found no support for the "hypothesis that successful and failed species were inherently different in their invasive abilities." Typha spp. are troublesome aquatics weeds in North America, as is Cyperus papyrus in Africa and Asia, yet when naturalized in New South Wales they have shown no evidence of aggressive spread (Arthington & Mitchell 1986). Unknown intrinsic capacities of species that are not expressed in their current ranges may manifest in new environments. High genetic variability of founder populations has been proposed as making invasion more likely, but some of the world's worst weeds are sterile, clonally-propagating species - Salvinia, Eichhornia, Oxalis, etc. (Barrett & Richardson 1986). Propagule pressure (introduction effort) may affect success of introduction, but Karieva et al. (1996) analyzed an extensive data set on weeds of the northwest U.S., and found that neither initial extent of inoculation or velocity of spread were predictive of ultimate range. Success of previous introduction may have small predictive power - "So far the only consistent predictor is success in previous invasions." (Williamson 1999). However, failures of these species have never been analyzed, and Moulton & Sanderson (1999) found that previous introduction outcome did not predict success of passeriform introductions. Carp (Cyprinus carpio) is well-known for its ability to inhabit new regions (Courtenay 1993). Three strains have been introduced into Australia - Prospect,' Singapore,' and Boolara'. Only Boolara spread rapidly outside the area of introduction, however it is now in decline (Arthington & Mitchell 1986). Brooke et al. (1995) found that extrinsic forces are more important than the intrinsic properties of invading species, and found no evidence that early successes are intrinsically superior invaders.

Prediction is further compounded by the time lags between introduction or establishment and spread. This has been attributed to various causes, but in most cases time lags are likely an illusory artifact of the failure to account for changes in climate or anthropogenic disturbance regimes. Kowarik (1995) found the average time elapsed between woody plant introduction and escape into the wild is 147 years in Europe. Clearly, no amount of study short of multi-century, multi-site trials could test for this. Reasoning from this, anti-alien crusaders now consider all non-expanding introduced populations to be "incipient invasions."

The new selective pressures faced by immigrating species may cause genetic adaptation allowing dispersal. Changes in flowering time have been noted in invaders (Kowarik 1995). This continued adaptive evolution towards integration into new environments cannot be predicted.

Future changes in environment whether climatic or anthropogenic will affect the range, population and dispersal of species. The nature, direction and extent of these changes are unknown, and further confound prediction.

Williamson (1999) cites ten reasons why prediction may fail: target not precise enough, significance statistical but not useful, extrapolation fails, statistical shrinkage, base rate effect (disproportionate false positives), new variables, lack of phylogenetic correlation, time lags, non-linearity and chaos, and complexity and situation-specific detail.

"All the theory pertaining to invasions developed to date assumes that there is a community with knowable properties to be invaded. If the community that is to be invaded is itself sufficiently variable, the predicting anything about an invasion will assume the status of a weather report." (Roughgarden 1986)

Although predicting establishment and dispersal is biologically problematic, attempts have been made to develop predictive models for assessing introduced species (Reichard & Hamilton 1997; Rejmanek & Richardson 1996). Although superficially appearing to have some success, a critical examination in light of the above points reveals serious inadequacies. Statistical analysis is no better than the data analyzed, and the subjective, anecdotal, qualitative and contaminated information-pool characterizing invasion biology is inadequate for accurate analysis. Failure to factor in anthropogenic disturbance, introduction effort, adequate lag time, suitability of habitat and failure to operationally define invasion (apparently, mere establishment = "invasion") are further problems. Although these models were explicitly designed to apply to regulatory control of the movement of species based on the presumed harmfulness of invaders, there was no consideration of the type of impact on the recipient ecosystem, degree of ecological integration, positive interactions with other species or positive effects on ecosystem function, or conservation value of introduced populations. An unacceptably high rate of false positives is also apparent.

Clearly, this brief overview of the difficulty or impossibility of predicting "invasion" illustrates that the NISC plans for implementing "comprehensive screening" are scientifically unjustifiable. In their current status, models predicting "invasiveness" have all the legitimacy and accuracy of a newspaper astrology column. They are naive at best, and at worst will be a disaster, another expensive boondoggle, hamstringing scientific research and valuable conservation efforts, and will serve to discredit legitimate governmental regulation.


Clearly, no "invasion crisis" exists which would warrant such sweeping changes to public policy. The effects of "invaders" on natural areas do not warrant any massive intervention, but a careful, case-by- case consideration. Clearly, "invasiveness" cannot be effectively predicted, and any system of pre- screening species will constitute an unacceptable roadblock to scientific research and conservation efforts, as well as going down in history as yet another porkbarrel boondoggle. We cannot afford to hamstring our scientific community with hastily-imposed regulatory roadblocks which are based on a popular hysteria, not sound science, and implemented via a fictitious ability to predict invasiveness. Our research and conservation communities need ready access to the earth's biological diversity. Unnecessary and unjustifiable roadblocks to the free movement of biological materials will hamstring many areas of research and important conservation efforts. It will increase our dependence on foreign supplies of raw materials and decrease our competitiveness in world markets. It will slow the important work of diversifying our agriculture, and prevent the ex situ conservation of important germplasm resources. The weedy relatives of crop plants are a vital reservoir of genetic material used in crop breeding. With the advent of genetic engineering, the entire biota of the earth is a possible source for these genes. [Note: I am personally opposed to genetic engineering.] We cannot afford to cut ourselves off from the rest of the world. Even amateurs have an important role to play, as witnessed by the number of endangered species preserved in their gardens and by their efforts alone. The discovery of important genetic variability in Sophora toromiro, now extinct in the wild, in the hands of a Chilean nurseryman and other individuals outside of botanic gardens points to the importance of not restricting public access to biological diversity (Maunder 2000).

If the Executive Order mandates risk analysis, prescreening of all species simply cannot be justified.

Invasion biology has been demonstrated to be a pseudoscience (Theodoropoulos 1999). Examination of the origins of "natural" communities, ongoing natural movements of species, and the plasticity of natural successional trajectories demonstrates that the concepts of "nativeness" and "alienness" on which invasion biology rests are non-operational constructs dependent on arbitrary spatial and temporal scales, and useless in the construction of testable scientific theory. In invasion biology literature, concepts are redefined at will, and all data are reinterpreted to support the theory of harm resulting from "invasion." The literature of invasion biology is a deeply contaminated information-pool, with low standards of evidence, unsupported causal attributions, circular reasoning, selective data-mining, high dependence on anecdotal reports, undefined jargon, unfalsifiable hypotheses, and other pseudoscientific characteristics. Results depend on highly subjective judgements and are for the most part based on anecdotal reports. Dire warnings of harm from "invaders" are for the most part purely speculative. Invasion biology displays an extraordinary lack of rigor. Contradictory evidence is resisted, as witnessed by the failure of the NISC to include data on the beneficial effects of anthropogenically-dispersed species, or opposing views of anthropogenic dispersal. Public policy must be founded on objective reality, or its effects will be harmful and expensive, as witness the disastrous Mirex program.


  1. What is the nature of the methodologies proposed for "comprehensive screening? What is the scientific basis for such methodologies? If methodologies have not yet been developed, on what factual basis does the NISC presume that they can be developed? How does the NISC propose to overcome each of the enormous obstacles to accurate prediction of "invasiveness" which are detailed above? On what factual basis does the NISC believe that such methodologies may be developed within the proposed schedule for implementation? What level of accuracy will be deemed acceptable, and what percentage of false positives will be acceptable, and how were these levels determined? How will the adopted methodologies be tested in the real world?
  2. What operational definitions has the NISC established for key terms, such as "native", "alien", "invasion", "harm", etc? These must be operational definitions, suitable for constructing testable scientific theory, and based on objective, measurable criteria which may be universally applied, and objectively identified in the field. What temporal and spatial scales will be employed in these definitions, and what objective and factual basis exists for using them? If arbitrary and subjective definitions are to be employed, on what basis does the NISC believe that they will be adequate for the formulation of public policy?
  3. What are the NISC's criteria for "ecological harm?" Again, these must be objective and measurable, not mere subjective speculation, and applicable to all species inhabiting a community, regardless of putative native or alien status. In the absence of such criteria, on what basis does the NISC intend to determine which species to control or exterminate?
  4. What objective ecological criteria identify "invaders?" These must be sufficiently precise to allow any biologist to identify the "invaders" in an ecosystem through the measurement of the criteria, without prior knowledge of putative native or alien status. For example, they must allow distinguishing between "native" and "alien" monocultures, between expanding native and alien populations, and between the ecosystemic effects of native and alien species. If such objective criteria cannot be developed, this will demonstrate the entirely subjective and pseudoscientific nature of invasion biology. In the absence of such criteria, on what basis does the NISC justify actions taken against putatively "alien" species?
  5. How will the NISC determine the cause of "invasion?" If anthropogenically-dispersed species are only present as the result of disturbance, will their extermination solve the "problem," or will this just create a downward spiral of inappropriate intervention? Treating symptoms and not underlying causes is a recipe for disaster.
  6. What attempts has the NISC made to fully inform the community of botanic gardens and zoological gardens of the full ramifications of comprehensive screening? How has the NISC solicited informed comment from these interested parties? What will the costs of screening be? Will even herbarium specimens have to be sterilized to insure non-viability of seeds or spores? How will this affect taxonomists needing living material for critical study? Will the NISC insure that adequate funding be made available to these grossly under-funded institutions? At a time when we should be greatly expanding the number of species maintained in these repositories, how will placing roadblocks in front of those who are "loading the arks" benefit the conservation of biological diversity?
  7. How will NISC policies affect the important conservation strategies of translocation and ex situ conservation? When the creation of hyperdiverse preserves through species packing in safe new environments would appear to be an essential conservation strategy, how will placing roadblocks before such efforts benefit the conservation of biological diversity?
  8. How will the NISC distinguish the harmless or beneficial establishment of a new species from "invasion," particularly in the early stages? If all new species are seen as "incipient invasions," and exterminated, valuable opportunities for ex situ conservation will be lost. What protocols has the NISC proposed for determining the conservation value of new populations of species which have been moved outside their historic ranges? Or does the NISC consider all such populations to be "invasions" to be exterminated without regard for their possible conservation value? For example, does the NISC, in common with other anti-"alien" extremists, consider introduced populations of the highly restricted at- risk endemic Cupressus macrocarpa "invasions" which must be exterminated? Certainly the mere presence of a species cannot be considered evidence for need to control. Does the NISC consider the mere presence of a species alleged to be non-native to be sufficient evidence for control or extermination? If so, on what factual basis does the NISC take such a position? If mere presence is not considered sufficient evidence for action, what are the criteria for action? Who will make these decisions, and under what authority? If there are disagreements as to whether a species is harmful, how will such disagreements be adjudicated? What processes will be put in place to insure that harmless species, or species of ex situ conservation value are not the object of harmful control or extermination measures?
  9. What attempts has the NISC made to contact and fully inform new crops researchers and economic botanists of the ramifications of their policies? How has the NISC solicited informed comment from these interested parties? How will the NISC insure that these workers have continued ready access to germplasm, particularly of important weedy wild relatives of crop plants? Considering that economically important new crops such as amaranth and St. Johnswort were considered weeds mere decades ago, how will researchers of the future develop such crops if denied access to germplasm? Since some weeds and pests may have important undiscovered value, such as the valuable hepatoprotective compounds discovered in recent decades in milk thistle (Silybum) or the recent discovery of bioactive compounds in many species of insects such as the Colorado potato beetle, how will this research proceed if populations of such currently undesirable species are exterminated?
  10. What attempts has the NISC made to hear skeptical voices and insure that all sides of the issue are fully and accurately presented to the public?
  11. How has the NISC evaluated the possible harm to ecosystems from the greatly increased use of herbicides and other methods of control of species? What protocols will be instituted to insure that benefit will outweigh harm? What long-term monitoring of both the introduced species and the proposed methods of control will be instituted to insure that the introduced species is actually causing harm, that the possible beneficial effects of the new species are not overlooked, and that the proposed methods of control will not be harmful in themselves? Long term monitoring will be essential on a site-by-site basis, due to the fact that each species behaves differently on each site, and each site has entirely new sets of conditions and ecological interactions. How will such monitoring be funded? If funds for monitoring are not available, will extermination or control projects be allowed to proceed?
  12. Has the presence of certain interested parties (such as an herbicide manufacturer's representative), and the exclusion of other interested parties compromised the objectivity of the NISC? What actions has the NISC taken to insure all stakeholders are represented?
  13. What form of independent oversight exists to determine that the NISC is fully and objectively informing the public and research communities of all facets of this complex issue, and to prevent the NISC from abusing its authority?

These are just a few of the questions which need to be answered - many more are implied by the information presented above. There are many other aspects of the Management Plan which deserve closer scrutiny that I have been unable to address here due to time constraints.

Clearly, insufficient time has been allowed for evaluation of the claims and proposals of the NISC. We must demand a "cooling off" period during which the NISC makes honest attempts to fully inform the public and research communities of the full ramifications of its proposals, and makes an honest attempt to hear the increasing number of skeptical voices in the academic community. We must allow time for the current "invasion" hysteria to cool off. The number of skeptical papers being published in invasion biology is on the rise. We are clearly on the verge of a "paradigm shift," and the hysteria which has characterized its proponents will give way to more reasoned and balanced approaches. Just as the harmful predator control and fire suppression policies of the past have given way in the face of new evidence, invasion biology must be discarded.

D. Theodoropoulos
Las Sombras Biological Preserve
Star Route 2, Box 337
La Honda, CA 94020-9733


Albert, S., and T. Trimble. 2000. Beavers are partners in riparian restorations on the Zuni Indian Reservation. Ecological Restoration 18:87-92.

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