. . . a short list of respected thinkers . . .
For full article see here
(Section Title Slide) Given the current level of hysteria on this subject, it's time for a reality check.
Purple loosestrife [Lythrum salicaria], the poster weed of invasion hysteria, is said to be aggressive, forming dense, monotypic stands, displacing native vegetation and destroying waterfowl habitat, quote "reducing its wildlife value to roughly that of a parking lot" (Bright 1998). The NISC [National Invasive Species Council] places it in their top ten invaders. Bright calls the plant a "monster." Not one of these claims is true. Whitt and coworkers (1999) studied 258 plots and found higher avian densities in loosestrife stands than other vegetation types, including ten breeding species. Treberg and Husband (1999) studied 41 plots and found no significant difference in vascular plant species richness, regardless of the percentage of loosestrife cover. A number of native species were found more likely to grow in plots containing purple loosestrife. Hager and McCoy (1998) traced the history of purple loosestrife and found little scientific evidence that it has deleterious effects, and state that, quote "there is currently no scientific justification for the control of loosestrife."
Saltcedar [Tamarix spp.] is said to be a disastrous ecological menace, one of the nation's worst weeds, changing river hydrology, increasing flooding, sedimentation, and salinization, crowding out cottonwood [Populus deltoides] and willow [Salix spp.], and driving native species "to the edge" (Malakoff 1999; U.S. Congress Office of Technology Assessment 1993). Yet, studies have demonstrated that native seedlings are competitively superior to saltcedar (Sher et al. 2000), and that it establishes in soils too saline for natives to germinate (Anderson 1996). Stromberg (1998) found that saltcedar actually enhances floristic diversity - herbaceous species richness and cover is significantly greater in saltcedar than cottonwood, and stem densities of native woody successional species are equivalent. Anderson (1998) has found that avian species richness and density in saltcedar is equivalent to native vegetation, and "biomass and diversity of insects in saltcedar stands is comparable to those in cottonwood and willow."In fact, 90% of the endangered willow flycatcher [Empidonax traillii extimus] nest in saltcedar (Malakoff 1999). Over 20 years ago Everitt (1980) pointed out that saltcedar is only a symptom of abuse of riparian areas, and he has recently stated that quote"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). These are not biased people - all have killed saltcedar during riparian restorations.
Eucalyptus [Eucalyptus spp.] is said to invade and destroy native ecosystems, killing plants and birds - quote:
"Their silent beauty masks a quiet destructiveness, for they are among the most monstrous organisms on earth. Outside of their native Australia, their leaves and bark are so toxic that they kill all plants around them and ensure that there will be no competition" (Ward 1994).
The cost of invaders was placed by Pimentel and coworkers (2000) at $137 billion annually in the US, and this figure has become one of the most widely quoted "facts" on invasion. Yet this figure is entirely fictitious - damage from cats, fully 12% of the total was fabricated out of thin air, and has no factual or economic basis whatsoever. They claim that St. Johnswort [Hypericum perforatum] is a quote "newly introduced non-native plant" when 5 minutes in a library would show that it has been present here for probably two centuries, nearly complete bio-control achieved 50 years ago, and the plant is a multi-million-dollar medicinal crop with compounds showing activity against HIV. Pimentel's paper has zero credibility.
The second-most quoted "fact" about invasion - that invaders are the "second greatest threat to biodiversity", or "the second greatest cause of endangerment" is equally vacuous. Matt Chew (2002) has investigated the origin of this claim and found that there is zero hard data to back it up - it is based entirely on anecdote and supposition.
I repeat, there is no credible evidence that this is true.
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