[APWG] Fw: The Overstory #196--An introduction to pathways for plant introduction

[Patricia_DeAngelis at fws.gov]

Patricia S. De Angelis, Ph.D.
Botanist - Division of Scientific Authority
Chair - Plant Conservation Alliance - Medicinal Plant Working Group
US Fish & Wildlife Service
4401 N. Fairfax Dr., Suite 750
Arlington, VA  22203
703-358-1708 x1753
FAX: 703-358-2276
Working for the conservation and sustainable use of our green natural 
resources.
<www.nps.gov/plants/medicinal>

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Subject
The Overstory #196--An introduction to pathways for plant introduction






Publication date: September 17, 2007



The Overstory #196--An introduction to pathways for plant introduction
     by Nick Pasiecznik, Agroforestry Enterprises, France



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NEW! Invitation for article submissions to The Overstory: 
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The Overstory #196--An introduction to pathways for plant introduction
     by Nick Pasiecznik, Agroforestry Enterprises, France


Contents:

: BACKGROUND
: THE GEOGRAPHY OF PLANT INTRODUCTIONS
: INTENTIONAL INTRODUCTION
: --> Plants for commercial production
: --> Plants for protection
: --> Ornamental plants
: ACCIDENTAL INTRODUCTION
: --> Traded food and fodder
: --> Traded animals and animal products
: --> Traded timber, packaging, ores and building materials
: --> Attached to man and machinery
: MEASURES FOR REDUCING PLANT INTRODUCTIONS
: REFERENCES
: ORIGINAL SOURCE
: ABOUT THE AUTHOR
: WEB LINKS
: RELATED EDITIONS OF THE OVERSTORY
: PUBLISHER NOTES
: SUBSCRIPTIONS


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BACKGROUND

Plants move. Vast native ranges support this. They don't pick up their
roots and walk, although some whole plants may occasionally be
transported naturally by storm or current, and there are many
free-floating or loosely-fixed aquatics. Rather, they tend to spread
inter-generationally, slowly, over time. Although the rate of movement
through natural dispersal of seed or other propagules is assumed to be
generally very small, there are important but infrequent long-distance
dispersal events, thanks either to wind or water, or with the aid of
animals. Thus in geological history, besides the slow 'creep' in the
spread of plants, there were occasional long-distance pathways for plant
introduction (and subsequent 'invasion', where the new arrival was
better adapted to local conditions than existing species). These would
have tended to follow geographical and migratory pathways, or
'corridors'.

The earliest travels of man would have aided the spread of plants, most
likely unconsciously at the outset, with seed discarded en route or
stuck to hair and furs, then consciously, by bringing along fruit and
seeds of plants known to be edible, as he migrated. It is considered
that this may have also been a pre-historical beginning to plant
selection, as it is likely that it was the seeds of sweeter fruit that
were preferentially eaten and spread, accidentally or intentionally.
Although there is some evidence to suggest limited intercontinental
introduction of plants by man between the Americas, Australasia and the
Old World before 1500, there are compelling records of the spread of
plants within and between Asia and Europe, also Africa, as human
civilization advanced, certainly from 5000 years ago. Such movements
followed advancing armies and tribal displacements, but increasingly
occurred along developing trade routes. While most plants transported
would have been those that were being traded, such as cereals or spices,
they would have, as today, contained other seeds. Also, the horses, oxen
and camels that carried these commodities are very likely to have
transported seed along these same pathways themselves.

These widespread, pre-historical movements have made it very difficult
to identify the origin, or true native range, of many species. While
this is especially true of crops, it must surely also be true of crop
weeds and forage plants. The 'fertile crescent' in Mesopotamia,
modern-day Iraq, is often regarded as the birthplace of settled
agriculture, beginning about 10,000 years ago, and many crops are said
to be native to this region. However, the true origin of many species
could be further afield, with the crops 'discovered' elsewhere and only
domesticated there. The grapevine (Vitis vinifera) is one of these, with
recent research now indicating its origins in the Caucasus, and
assessing the exact origins of other crops is sometimes little more than
historical guesswork. A look at the literature on the origin and spread
of common Mediterranean trees such as the almond (Prunus dulcis), carob
(Ceratonia siliqua), fig (Ficus carica), olive (Olea europaea) and
pomegranite (Punica granatum) are educative in this regard.

The introduction of all invasive species, not only plants, has closely
paralleled the development of trade routes in the direction of travel,
and the number of different species and the number of individuals
introduced is positively correlated to the increasing quantities being
traded. In addition, the accurate recording of presence/absence of plant
species is also closely tied to development of knowledge and language
and as such we can only rely with any certainty on information from the
relatively recent past for most plants, other than important crops. It
is with this in mind that this paper aims to identify present-day
pathways for human-associated introduction and spread of terrestrial and
aquatic plants.


THE GEOGRAPHY OF PLANT INTRODUCTIONS

The geographical routes or corridors along which plants are introduced
should require little analysis, but are presented here to confirm that
plants and their propagules follow the movement of people, animals,
water and wind (e.g. Ridley, 1930). Natural pathways for long-distance
dispersal follow rivers, ocean currents and migratory routes. Artificial
pathways, which are emphasized in this paper, follow oceanic, overland
and aerial trade and passenger routes. Overland, these tend to follow
natural courses. Roads, railways and canals are often built along rivers
and valleys, over mountain passes or around coasts, and as such may not
differ greatly from natural pathways. On the seas and oceans, trade has
expanded greatly in the past thousand years, but the routes have
remained largely unchanged since the advent of powered ships (c. 1900),
which allowed independence from seasonal winds, though use of currents
still reduces fuel requirements. Other previously seasonal routes such
as those frozen in winter months, e.g. the St Lawrence river, are now
kept open all year with ice-breakers. Other new oceanic routes have
followed the construction of new channels, e.g. the Suez and Panama
canals; the elimination of piracy, e.g. in the Strait of Malacca; or new
(or resumed) trading partners, e.g. Japan after the Meiji Restoration,
Eastern Europe after the Cold War, or the exponentially increasing trade
with China today. The advent of aviation has opened new routes largely
independent of all factors already considered, and which now criss-cross
and connect the globe.


INTENTIONAL INTRODUCTION

It has been estimated that over 70% of all invasive exotic terrestrial
plant species were intentionally introduced into the new areas now
invaded. In Australia, 46% of serious weeds were deliberately introduced
for particular purposes (Panetta, 1993). This very high proportion has
significant impacts for attempting to control entry in the traditional
sense of phytosanitary measures, i.e. they are mostly not accidentally
introduced as crop contaminants as are many arthropods pests and crop
pathogens. Most invasive plants have been introduced for perceived
benefits in terms of production (e.g. as agricultural crops for food,
fodder or fibre, fuel or timber trees or medicinal plants), for
protection (e.g. for hedging or erosion control) or as ornamental
species. As such, the pathway for all these can be regarded as much the
same, though the organization or individual responsible (the 'vector')
may differ, e.g. commercial nurseries, governments, plant collectors,
manufacturers, etc. There are important distinctions between vectors
when considering means of regulation. Most of these are transparent,
legal introductions through regulated channels, others are legal or
illegal, often via baggage or the postal service.


--> Plants for commercial production

Agricultural crops. There are a number of agricultural or horticultural
crop species or varieties that have appeared on lists of invasive weeds.
These include: carrot, chicory, endive, Jerusalem artichoke (Helianthus
tuberosus), okra, parsnip, pumpkin, radish, rice, rye, sorghum, turnip -
even the tomato (Tye, 2001), and this list is by no means exhaustive.
The inclusion of many of these crops as 'invasive' may surprise some,
but this highlights the premise that a weed is just 'a plant in the
wrong place'. All have been intentionally introduced around the world as
valuable crop plants, but which, as least somewhere, have now spread to,
and within, ecologically sensitive areas. Most are annual or biennial,
but some are perennial species. Also, besides the food crops listed,
there are invasive plants amongst species introduced for fibre (e.g
Arundo donax and Cannabis sativa), for herbs, condiments or medicinal
use. Some aquatic crops have also become invasive species, including
algae and seaweeds (e.g. Undaria pinnatifida) in marine environments,
and leafy vegetables (e.g. water spinach, Ipomoea aquatica) in fresh
water.

Fodder crops. This is another important group which includes
intentionally introduced invasive weeds, and in the grasses and sedges,
contains a number of the World's Worst Weeds (Holm et al., 1979). These
were often introduced for improved forage production by national
institutes, and which were either promoted and/or escaped from
cultivation. In Australia, 80% of the invasive grasses are thought to
have been introduced by the government and escaped from research
stations around the country. Important invasive grasses introduced this
way include elephant grass (Panicum maximum), kikuyu grass (Pennisetum
clandestinum), molasses grass (Melinis minutifolia), lolium ryegrass
(Lolium temulentum) amongst many others, though some may also have been
introduced as grain contaminants. Several fodder shrubs have also become
invasive after being introduced as potential dryland fodder species,
include saltbushes (Atriplex spp.) and Russian thistles (Salsola spp.).

Trees. Some tree species have been known as highly invasive within their
native ranges for over a century, such as mesquite (Prosopis spp.) in
the southern USA (e.g. Pasiecznik, 1999). More recently, many other
forestry trees have been noted as important invasive species where
introduced (e.g. Hughes and Styles, 1989; Hughes, 1994; Binggeli, 1996;
Richardson, 1998). They can be grouped into traditional forestry species
introduced and grown for timber (e.g. Eucalyptus and Pinus spp.),
agroforestry species introduced for multiple products (e.g. Acacia and
Leucaena spp.), fruit trees (e.g. Guajava), ornamentals (also covered
below) and trees introduced for other uses, such as tannin (e.g. the
black wattle, Acacia mearnsii), biofuel (e.g. the purge nut, Jatropha
curcas), etc. Over 400 tree species have been identified as invasive
outside of their native ranges (Haysom and Murphy, 2003). Trees are a
specific case not only due to their large size (and therefore their
subsequent impacts), but that they were almost entirely intentionally
introduced, and comprise a significant number of the plant species in
the World's Worst 100 Invasive Species (ISSG, 2007).


--> Plants for protection

Many plants that were introduced for productive purposes were also noted
to have perceived environmental or protective benefits. Most of these
were trees and shrubs which were noted as providers of shade, shelter,
hedging or to have soil binding or enriching qualities, such as species
of Acacia, Prosopis and many others. Some plants, were, however,
introduced principally for their protective function, including; erosion
control, soil-binding (dune stabilization), shade, hedging (living
fences) and as a cover for weeds, game, man or his machines.

Vetiver grass (Vetivera zizanioides) has been very widely promoted for
erosion control, as a sterile grass apparently not able to spread, but
there is now some evidence that it is able to revert to self-fertile
forms and is a potential invasive species. Other herbaceous species used
for soil binding have characteristics such as a well-developed surface
root system and low-growing, spreading habit, which are also the same
characteristics often associated with high-impact invasive species.
Grevillea robusta was introduced as a shade tree, often for coffee,
through in some countries it is a noted invasive species. Numerous
species have been introduced as hedging plants, and as they are often
thorny, become very undesirable weeds indeed, such as Acacia karroo,
Lycium ferocissimum and Ulex europeaus. Plants for ground cover are
expected to grow quickly and smother weeds, but therefore, may also
become weeds themselves, e.g. the mile-a-minute vine (Mikania micrantha)
that was introduced as a ground cover for tea, rubber and coconut
plantations. This species and others are also thought to have been
introduced around the Pacific in the second world war as a cover for
military positions.


--> Ornamental plants

The nursery trade has been estimated as the single biggest cause for the
introduction of invasive plants. Driven by a continuing global demand
for novel plants, it will without adequate control, certainly increase
its 'market share' as a pathway. A quick glance at any list of invasive
plants will indicate that a significant percentage are (or were!)
ornamentals. During the colonial period, settlers would often wish to
bring with them, or have sent to them, things to remind them of their
old 'home' country. Many of these were plants, and a number of these
found their new home so much to their liking that they 'escaped' and
have spread widely, such as the common ivy (Hedera helix) as an invasive
in New Zealand. Today, the trade and introduction of ornamental plants
is very big business, and expanding every year. Some, such as the
wandering Jew (Tradescantia fluminensis), is a very common ornamental,
probably present in most countries of the world, but only recently noted
as highly invasive in Australia and elsewhere.

Garden centres and other retail outlets are the centres from which
ornamental species spread within a country, and the nursery business
acts as the importer of seed or other propagative material thus being an
international pathway for terrestrial and aquatic plants. Catalogue mail
order supply of seed or even whole plants by the same or specialized
companies, greatly increases the potential for spread of invasive
ornamentals. The advent of internet-based mail order firms has also
massively enlarged the potential to an almost uncontrollable pathway for
further introductions. A recent ranking of the importance of various
pathways for the introduction of invasive plants into the USA,
classified "availability on web-based mail-order catalogues" as the
single most important reason for the potential introduction of new
invasive species (see below). Several of the worst invasive plants are
aquatic species introduced as ornamentals, such as water hyacinth
(Eichhornia crassipes) and water lettuce (Pistia stratiotes).

Botanical gardens and plant collectors have been seen as potential
centres of invasion, and concern for this has led to the development of
new codes of conduct, aimed specifically at preventing the unwanted
spread of species from material obtained from a botanical garden (e.g.
the St Louis Declaration; Anon., 2001). Of 300 new plant species
recently screened for introduction into New Zealand, 2% were
applications from botanical gardens (Williams et al., 2001). Individual
plant collectors are also responsible for some plant introductions,
either as ornamentals or botanical 'oddities' for their own garden or
conservatory, but as the frequency and numbers are very low, this is
unlikely to be a common cause for invasion.


ACCIDENTAL INTRODUCTION

Although accidental introduction is seen as having far less importance
than intentional introduction for the entry of invasive plants today, it
has been credited with the introduction of numerous highly invasive
species in the past, and is still significant in terms of aquatic plant
introduction. Many plant protection organizations have systems in place
for checking consignments for the presence of weeds and weed seeds that
may threaten agricultural production, but these are only recently being
adapted for regulating the far more numerous weeds of environmental
concern (e.g. Quinlan et al., 2003). Aquatic plants affecting freshwater
systems are considered under such revised systems, whereas regulations
for marine plants are under the auspices of various organizations,
almost on a pathway by pathway basis.


--> Traded food and fodder

One of the commonest pathways for the accidental introduction of
invasive terrestrial plants is as seeds contaminating grains, mainly
cereals for human food, but also as animal fodder. Several countries
routinely check importing consignments of cereals for the presence of
weed seeds. In 2001, Russian quarantine checked commodities for the
presence of 15 species of weeds, Ambrosia artemisiifolia, A.
psilostachya, A. trifida, Bidens pilosa, Cenchrus pauciflorus, Centaurea
repens, Helianthus californicus, H. ciliaris, Ipomoea hederacea, I.
lacunosa, Iva axillaris, Solanum carolinense, S. elaeagnifloium, S.
rostratum and S. triflorum (Moshalenko, 2001). In India, 19 exotic weeds
were intercepted in wheat grain imported in 33 ship-loads through ten
major ports in a 2-year period, and the entire consignment of 2.5
million tons was diverted to non-wheat growing areas for consumption
purposes. (Singh, 2001). The species were Avena sterilis, Brassica
kaber, B. tournefortii, Buglossoides arvensis, Carthamus lanatus,
Centaurea solstitialis, Echium plantagineum, Emex australis, Linaria
canadensis, Lupinus angustifolius, Malva neglecta, Medicago scutellata,
Monarda punctata, Papaver hybridum, Phalaris paradoxa, Polygonum
aviculare, Raphanus rapharnistrum, Rumex crispus and Vicia villosa.
There are numerous other examples.

Other traded seeds can also be contaminated, such as spices and
condiments, even bird seed. Examples include the potential introduction
of giant hogweed (Heracleum mantegazzianum) in cumin seed (Cuminum
cyminum) used as a condiment, and the introduction and spread of
Ambrosia artemisiifolia in Europe in bird seed.


--> Traded animals and animal products

Livestock imports may have contributed to species introductions, either
externally attached to hair or mud, such as with Bathhurst burr
(Xanthium spinosum) on horses, or internally as feed. Trade in fleeces
has also been implicated in the introduction of a range of species, as
seen with the number of introduced plants growing around sites that
imported wool, e.g. ragworts (Senecio spp.). Purple loosestrife (Lythrum
salicaria) may have been introduced into the USA on fleeces, or on live
sheep imported from Europe (Thompson et al., 1987). Whereas livestock
may not be considered as long-distance dispersal agents, they may
transport seed several hundreds of kilometres in extensive grazing
systems common in countries such as the Argentina, Australia and the
USA. Cattle muster stations and watering holes are often sites for
numerous plant species grown from seed deposited in faeces.
Historically, railheads in the USA were new foci for invasion of plant
species transported with cattle from pastures many hundreds of
kilometres further south. Intercontinental introduction has also been
suggested, via feeds taken on board ships carrying live animals.


--> Traded timber, packaging, ores and building materials

Trade in timber has rarely been implicated in the introduction of
plants, but seeds may be transported in mud or bark attached to logs.
Timber as a packaging has been recorded as a pathway, but straw and
other 'soft' packaging has been a more important pathway for the
introduction of some weeds. Examples include cheatgrass (Bromus
tectorum) and camelthorn (Alhagi maurorum), both thought to have been
introduced into the USA in straw used as a packing material (e.g.
Bottel, 1933). Various aquatic plants are also used for packing fish and
shellfish, and although this is an uncommon pathway, it was noted as the
means for the introduction of the sea grass Zostera japonica to the USA
from Japan (Ribera Siguan, 2003).

Soil, sand and gravel have all been implicated in the introduction of
weeds, either as ship's ballast or for use in the construction industry
or in road building, and also as media in the nursery trade. There is
evidence that Mikania micrantha has spread from island to island in the
Pacific through the trade in sand and gravel for construction purposes,
as seedlings have been seen to occur in freshly imported material. Road
building is often seen as a cause of introduction and spread, with the
importation of materials for making the road, and moving materials along
as construction continues. However, concerning spread (as opposed to the
introduction of new species), it must be difficult to separate
contamination of inert materials from the machinery itself as the
pathway. Examples include Impatiens glandulifera with river gravel in
Germany and many others. The transport of mineral ores from mines and
quarries may also act as pathways but their relative importance remains
unascertained.


--> Attached to man and machinery

In the same way that barbed seed or fruits attach to animal fur, they
may also attach to human clothing or accoutrements, and this is noted as
a significant means for the introduction of some species and spread of
others, such as cheatgrass (Bromus tectorum) on socks in the USA. Seed
or fruit unwittingly attached to travellers' belongings may be
transported internationally, this possibility now being much more likely
with the increase in the numbers and destinations of tourist and
business travellers, notably by air. The vehicles themselves may act as
the vectors, though this is much more probably with land-based
transport. Cars, buses and trains may carry mud containing seed, or odd
examples such as the vortex created by moving trains transporting
ragwort (Senecio spp.).

Far more likely to carry weed seeds are vehicles which work with or on
soil, such as farm and forestry machinery, construction equipment,
especially road-building machines, and mining machinery. These have been
implicated in the local dispersal of seed, but also long-distance
introduction of plants with international trade in private and public
vehicles. There are numerous studies that have looked specifically at
the role of 'war' as a pathway, including seeds attached to soldiers or
military vehicles. This was of special concern to Australian officials
concerning equipment and servicemen returning from East Timor following
the humanitarian work carried out there, and strict protocols for
cleaning and inspection were developed and implemented (Pheloung, 2003).


MEASURES FOR REDUCING PLANT INTRODUCTIONS

The first stages in preventing plant invasions are to first identify
which species are of concern, and where they presently occur. Then,
'pathway analysis' can be employed to identify by what means, what
routes and what potential points of entry the species may take to gain
entry into the area in question. Finally, it must be decided whether it
is desirable to prevent entry, and if so, whether this is possible with
the resources available, both practically and legally. For example, if
the plant is only likely to be introduced intentionally, then the
pathways are evident, being normal trade routes, with points of entry at
land borders, ports or airports, and any quarantine measures are
relatively easy to apply. What is difficult in this case is deciding
whether the species merits regulation, if the risks outweigh the
benefits, and the value of this trade or commercial production must be
taken into account. Stopping the intentional introduction of plants is
only possible if they are already regulated by the importing country,
which bans entry of the species.

Preventing accidental introduction follows well-developed systems
established and used by plant protection organizations for crop pests
and pathogens. First, identify the commodities that are likely to be
contaminated and apply the necessary quarantine measures, supported by
surveillance and monitoring. The secret is in correctly identifying the
priorities, as the resources available to the plant protection services
can never be enough to adequately control all imports and all pathways.
For example, how much time and effort should be applied to checking post
and strict controlling of personal belongings (noting that there will
always be exceptions, such as the 'diplomatic bag')? What about checking
all grain imports, or banning the importation of bird seed? These are
complicated decisions, based on the identification of the species posing
the greatest risk, their origin and potential impacts, and there are no
general or easy answers.

The exponential rise in the quantity of goods traded globally is very
likely to bring with it even more unwanted visitors in the form of
potentially invasive species. Stopping all trade or travel is clearly
not an option and so entirely preventing the further introduction of
potentially invasive plants along these well-trodden pathways is not
possible. However, some levels of risk-reduction can be implemented, and
will need to be integrated with all other management measures to
maximise this effectiveness.


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REFERENCES

Anon., 2001. Linking ecology and horticulture to prevent plant
invasions. Selections from the proceedings of the workshop at the
Missouri Botanical Gardens, December 2001. St Louis, Missouri, USA:
Missouri Botanical Gardens. http://www.mobot.org/invasives/mbgN.html.

Bottel AE, 1933. Introduction and control of camelthorn. Monthly
Bulletin of the California Department of Agriculture, 22:261-263.

Binggeli P, 1996. A taxonomic, biogeographical and ecological overview
of invasive woody plants. Journal of Vegetation Science, 7(1):121-124.

Haysom KA, Murphy ST, 2003. The status of invasiveness of forest tree
species outside their natural habitat: a global review and discussion
paper. Forest Health and Biosecurity Working Paper FBS/3E. Forestry
Department. FAO, Rome.

Holm LG, Plucknett DL, Pancho JV, Herberger JP, 1979. The World's Worst
Weeds. Distribution and Biology. Honolulu, USA: The University Press of
Hawaii.

Hughes CE, 1994. Risks of species introductions in tropical forestry.
Commonwealth Forestry Review, 73(4):243-252, 272-273.

Hughes CE, Styles BT, 1989. The benefits and risks of woody legume
introductions. Monographs in Systematic Botany from the Missouri
Botanical Garden, 29:505-531.

IPPC, 2003. ISPM No. 11, Revision 1. Pest Risk Analysis for Quarantine
Pests including Analysis of Environmental Risks. Rome, Italy:
International Plant Protection Convention, FAO.

ISSG, 2007. The world's worst 100 invasive species. The Global Invasive
Species Programme. The Invasive Species Specialist Group, IUCN.
Auckland, New Zealand: The University of Auckland.

Moshalenko GP, 2001. Quarantine Weeds of Russia. Ministry of
Agriculture, Moscow, Russia. 278pp.

Panetta E, 1993. A system for assessing proposed plant introductions for
weed potential. Plant Protection Quarterly, 8:10-14.

Pasiecznik N, 1999. Prosopis: pest or providence, weed or wonder tree?
ETFRN News 28:12-14.

Pheloung P, 2003. An Australian perspective on the management of
pathways for invasive species. In: Ruiz GM, Carlton JT, eds. Invasive
Species: Vectors and Management Strategies. Washington DC, USA: Island
Press, 249-269.

Quinlan MM, Pasiecznik NM, Sastroutomo SS, 2003. Assessing the
environmental risks of invasive species using ISPM No. 11 (Rev. 1):
where to start. International Workshop on Invasive Alien Species and the
IPPC, 22-26 September 2003, Braunschweig, Germany. FAO, Rome: the
International Plant Protection Convention.

Richardson DM, 1998. Forestry trees as invasive aliens. Conservation
Biology, 12(1):18-26.

Ridley HN, 1930. The Dispersal of Plants throughout the World. Ashford,
Kent, UK: L. Reeve, 744 pp.

Ribera Siguan MA, 2003. Pathways of biological invasions of marine
plants. In: Ruiz GM, Carlton JT, eds. Invasive Species: Vectors and
Management Strategies. Washington DC, USA: Island Press, 183-226.

Singh S, 2001. Interception of weeds in imported wheat grain
consignments. Annals of Agricultural Research 22(1):83-87.

Thompson DQ, Stuckey RL, Thompson EB, 1987. Spread, impact, and control
of purple loosestrife (Lythrum salicaria) in North American wetlands.
United States Fish and Wildlife Service, Fish and Wildlife Research No.
2. Washington DC, USA: United States Department of the Interior.

Tye A, 2001. Invasive plant problems and requirements for weed risk
assessment in the Galapagos Islands. In: Groves RH, Panetta FD, Virtue
JG, eds. Weed Risk Assessment. Collingwood, Australia: CSIRO Publishing,
153-175.

Williams, PA, Nicol E, Newfield M, 2001. Assessing the risk to
indigenous biota of plant taxa new to New Zealand. In: Groves RH,
Panetta FD, Virtue JG, eds. Weed Risk Assessment. Collingwood,
Australia: CSIRO Publishing, 100-116.


::::::::::::::
ORIGINAL SOURCE

This article was excerpted and revised with permission from the author
and publisher from:

Pasiecznik, N. 2004. Pathways for plant introduction. In: CABI, Crop
Protection Compendium. <http://www.cabi.org/compendia/cpc>.

For more information about the Crop Protection Compendium, visit:
<http://www.cabi.org/AllOtherProducts.asp?SubjectArea=&PID=106>
or contact:
CAB International
Wallingford, OX10 8DE, UK
Fax: +44 1491 833508
E-mail: compend at cabi.org 

CABI is also developing an Invasive Species Compendium
For further details, visit:
<http://www.cabi.org/datapage.asp?iDocID=180>


:::::::::::::: 
ABOUT THE AUTHOR

Nick Pasiecznik is managing consultant for Agroforestry Enterprises,
specialising in research, development and training in agroforestry,
drylands, timber processing, and is a leading expert on Prosopis
species. Other interests and experience include forestry, agriculture
and land-use systems, organic production, invasive species and plant
taxonomy.

Nick Pasiecznik
Agroforestry Enterprises
Villebeuf
71550 Cussy-en-Morvan
France

npasiecznik at wanadoo.fr
+33 (0)3 85546826


::::::::::::::
WEB LINKS

The Entomology and Forest Resources Digital Information Work Group
Invasive species page: <http://www.invasive.org/>

The Nature Conservancy alien species links:
<http://tncweeds.ucdavis.edu/links.html>

Hawaiian Ecosystems at Risk Project (HEAR): <http://www.hear.org/>

Weeds Gone Wild: Alien Plant Invaders of Natural Areas is a web-based
project of the Plant Conservation Alliance's Alien Plant Working Group:
<http://www.nps.gov/plants/alien/>

Invasive Woody Plants - World Species List:
http://members.lycos.co.uk/WoodyPlantEcology/invasive/worldlist.htm


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RELATED EDITIONS OF THE OVERSTORY

The Overstory #153--Online species references
The Overstory #113--Forest Biodiversity
The Overstory #89--Invasive Woody Plants
<http://www.agroforestry.net/overstory/overstory89.html>


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ANNOUNCEMENTS


NEW! Invitation for article submissions to The Overstory: 
<http://www.agroforestry.net/overstory/ovsubm.html>
 

ADDRESS CHANGES: Please send any changes in your e-mail address to 
overstory at agroforestry.net


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PUBLISHER NOTES


Publisher: Permanent Agriculture Resources
Editor: Craig R. Elevitch

Distributor:
The Overstory is distributed by Agroforestry Net, Inc., a nonprofit
501(c)(3) organization based in Hawaii.
Address: P.O. Box 428, Holualoa, Hawaii 96725 USA
Email: overstory at agroforestry.net ; Web site:
http://www.overstory.org 

Past editions of The Overstory: http://www.overstory.org 

This publication is Copyright 2007 Permanent Agriculture Resources.
All Rights Reserved Worldwide. For Conditions of Use please contact
overstory at agroforestry.net or write to Agroforestry Net, Inc. at the
address above. 

This journal is designed to provide agricultural information, but
is sent with the understanding that the editors and publishers are
not engaged in rendering consultation. If expert assistance is
required, the services of a professional should be sought. 


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