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Non-native wildlife risk
assessment: a call for
scientific inquiry
Carrete and Tella (Front Ecol Environ
2008; 6[4]: 207–11) found that former pet birds that had been captivebred were less likely to establish
invasive populations than wildcaught pet birds. Although focused
exclusively on Spain, their findings
are timely and important in the context of risk assessment of non-native
wildlife in the US. On June 26,
2008 the House Natural Resources
Committee’s Subcommittee on Fisheries, Wildlife, and Oceans held a
legislative hearing on the NonNative Wildlife Invasion Prevention
Act (House Resolution 6311; hereafter, the Bill), a bill intended to
“prevent the introduction and establishment of non-native wildlife
species that negatively impact the
economy, environment, or human or
animal species’ health, and for other
purposes”. If passed in its current
form, the Bill would require the US
Fish and Wildlife Service (FWS) to
conduct risk assessments of all
imported species of non-native
wildlife and limit entry to those
species deemed unlikely to become
invasive in the US.
Despite a growing interest in risk
assessment as a means of preventing
biological invasion (eg Kolar and
Lodge 2001), evaluations have largely incorporated natural history information from a species’ native range
and have not considered risk differential below the species level.
Carrete and Tella’s work points to a
need to explore variation among and
within species due to reproductive
origin (captive bred or wild caught)
and possibly even more specific factors (eg morphological variations
such as albinism). Jakes et al. (2003)
found that 100% of brown tree
snakes (Boiga irregularis) from island
States were free of Hepatozoon boigae
parasites, whereas 44% of those from
northern Australia were parasitized,
suggesting the potential for populawww.fr ontiersinecology.or g
tion-level risk variation of species
and/or their hitchhikers.
In the context of the draft Bill, it is
also incumbent on social scientists
and policy makers to proactively
determine whether the proposed regulation could achieve its stated goals.
Rivalan et al. (2007) and Cooney and
Jepson (2006) found that wildlife
trade bans can increase trading activity, act counter to equity and sustainability values, and be less effective than market-led management.
Because regulations are only as effective as stakeholder compliance, it is
imperative that the most affected
constituencies (ie pet/aquaria, aquaculture, and livestock industries) support the Bill’s final provisions, if
enacted. The Pet Industry Joint
Advisory Council has endorsed a
recent ban on Gambian pouched rats
(Cricetomys gambianus) and other
African rodents by the Centers for
Disease Control and Prevention, but
from 1973 to 1975, strongly opposed
a FWS-led initiative to prohibit the
import of non-native species until it
could be proven that the organisms
posed a low risk of bioinvasion (M
Meyers pers comm). Although issues
of transparency, scientific integrity,
and regulatory consistency are generally assumed to be important criteria,
studies that explicitly evaluate the
parameters that contribute to stakeholder support for wildlife regulations
in the US are warranted.
Finally, there is a need for collaboration across the biological and social
sciences to define the “likelihood”
and “unlikelihood” of non-native
species establishment in quantitative
terms, as well as to determine how
cost–benefit analyses and risk mitigation measures (eg sterilization) – relative to non-native wildlife importation – will be evaluated and
incorporated into decision making.
Although steps toward a comprehensive, risk-based assessment of nonnative species imports were outlined
in the first US National Invasive
Species Management Plan (NISC
2001) 7 years ago, it will likely take
at least a few more years for the Bill
or similar legislation to be enacted.
In the interim, there is ample opportunity for research scientists and
granting agencies to help ensure that
the product takes into account the
best available data, scientific knowledge, and assessment processes.
Jamie K Reaser
Ecos Systems Institute,
Stanardsville, VA
(ecos@nelsoncable.com)
Cooney R and Jepson P. 2006. The international wild bird trade: what’s wrong
with blanket bans? Oryx 40: 1–6.
Jakes KA, O’Donoghue PJ, and Whittier J.
2003. Ultrastructure of Hepatozoon
boigae (Mackeraas, 1961) nov comb
from brown tree snakes, Boiga irregularis, from northern Australia. Parasitol
Res 90: 225–31.
Kolar CS and Lodge DM. 2001. Progress in
invasion biology: predicting invaders.
Trends Ecol Evol 16: 199–204.
NISC (National Invasive Species Council).
2001. National invasive species management plan. www.invasivespeciesinfo.
gov/council/mp2008.pdf. Viewed 17
Sep 2008.
Rivalan P, Delmas V, Angula E, et al. 2007.
Can bans stimulate wildlife trade?
Nature 447: 529–30.
The authors respond
We acknowledge Reaser’s interest in
our work on predictors of avian invasions (ie the wild-caught origin of
pets), and their discussion of the usefulness of such predictors within the
context of US law as well as encouragement of further risk-based assessment of imports of non-native
species. Our study was restricted to
Spain, so more research is needed
before we can generalize across taxa
and regions. Here, we aim to broaden
the implications of our study by presenting alarming data on the international animal trade, and by discussing
aspects linked to failures when generalizing our results for countries with
different social attitudes.
The literature on animal reintroductions and temperaments suggests
that not only birds but most pet vertebrates could be more likely to
become invaders when they are
wild-caught than when they are captive bred (Front Ecol Environ 2008;
© The Ecological Society of America
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© The Ecological Society of America
467
100
2 500 000
Number of individuals
(n = 94)
2 000 000
80
1 500 000
60
1 000 000
(n=142)
40
(n=124)
20
500 000
(n = 1)
(n = 7) (n = 17)
Percentage of wild individuals
(n = 27)
0
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6[4]: 207–11). The large number of
animals currently being transported
across borders to satisfy the demand
for pets in developed countries is
therefore of grave concern. Data on
exporting quotas in 2008 from the
Appendices of the Convention on
International Trade in Endangered
Species of Wild Flora and Fauna
(CITES) are worrisome: nearly four
million individual animals, belonging to over 400 species and originating in 30 countries, are being traded
worldwide for the pet market (Figure
1), with most (70–100%, depending
on taxa) being wild-caught. We share
Reaser’s concern that wild-trade bans
could increase illegal trading, especially among high-value species
(Courchamp et al. 2006). However,
our 3-year monitoring of the Spanish
pet market following the European
Union wild-bird trade ban has not
shown evidence of illegal trading
(unpublished data). Even accepting
further upsurges, it is unlikely that
the level of trade seen in the year
prior to the ban (2004, in which
190 000 birds from 134 species were
imported by Spain) will be reached
(www.unep-wcmc.org/citestrade).
Finally, we would like to add that
our recommendation to filter exotic
pet species to avoid invaders can fail
when particular societal attitudes
bypass processes of natural selection.
The US social context seems to differ
greatly from other countries, such as
Spain, where the spread of exotic
birds is recent, and where some
wildlife agencies are taking actions to
control feral populations (eg in the
case of the invasive monk parakeet)
without popular opposition. In
Florida, however, feral populations of
parrots have been reported since the
1920s (Butler 2005), where over 75
species have been introduced and at
least 20 species are now breeding
(www.tropicalaudubon.org). Many
people appreciate parrots living in
their gardens and parks, and often
provide food and nest sites for them.
This may have contributed to the
spread of the invaders and increased
the difficulty of their eradication, as
seen in the invasive monk parakeet,
Figur e 1. Export quotas for specimens of species included in CITES for 2008. The left
axis represents the total number of individuals per taxa, while the right axis shows the
within-taxa average proportion (+ SD) of wild-caught traded individuals. Number of
species within taxa is in brackets. Original data were obtained from www.cites.org.
which is now distributed across 20
US states. The huge nests of this
species, often built on power utilities,
cause substantial economic losses.
However, local parrot preservation
associations oppose electric companies in legal actions to reduce populations or remove nests. Surprisingly,
a ban on feeding feral parrots in San
Francisco, CA, was recently approved in response to concerns about the
safety of the birds, rather than to
their invasiveness. It seems that
many parrot species would not have
established feral populations without
this enthusiastic public support, as
illustrated by budgerigars, a captivebred species showing low invasiveness in Europe (as described in our
original article in Frontiers), but with
feral populations in the US (Butler
2005). Budgerigars in Florida were
dependent upon both bird feeders
and nest boxes for their success, and
in Great Britain disappeared after the
individual who was feeding them
moved (Butler 2005). Such public
assistance for charismatic urban parrots is spreading in Europe, where
some supporters even claim that the
propagation of urban feral populations is a conservation tool for
endangered species (www.cityparrots.org). Therefore, although we
agree with Reaser that more research
and science-based laws are needed to
prevent invasions, efforts may be
futile until societies learn that alien
species should not be transplanted in
the first place.
Martina Carrete* and José L Tella
Estación Biológica de Doñana
(CSIC), Sevilla, Spain
*
(martina@ebd.csic.es)
Butler CJ. 2005. Feral parrots in the continental United States and United
Kingdom: past, present, and future. J
Avian Med Surg 19: 142–49.
Courchamp F, Angulo E, Rivalan P, et al.
2006. Rarity value and species extinction: the anthropogenic Allee effect.
PloS Biol 4: e415. doi: 10.1371/
journal.pbio.0040415
Ecologists,
environmentalists, and the
problem with labels
In a recent Guest Editorial (Front
Ecol Environ 2008; 6[7] : 347),
Donald Strong commented that it is
acceptable – and actually desirable –
for ecologists to be environmentalwww.frontiersinecology.or g
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468
ists and that this labeling has been
misused by interest groups using polarization and leverage to support their
“war on science”. I have struggled
with this issue for a long time. As an
ecologist, I expect society to respect
and acknowledge the products of my
field, especially because “good” ecology bases its conclusions on well-supported evidence. Ecology is also
openly self-critical, as any scientific
discipline must be. In fact, critical
evaluation of peer’s data, analyses, and
discussions is what helps our discipline
advance. I therefore believe that ecology deserves to play an important role
in society’s decisions and directions.
Ecologists – in studying, understanding, and caring for the environment –
provide an indispensable service to
society. If this means that ecologists
are environmentalists as well, then I
would welcome the label.
However, the problem with this
label is that it undermines the role of
ecologists in providing data and
information critical for society as it
proceeds (or, as some would say,
bumbles along) with making decisions that will affect this and future
generations, the sustainability of our
social and economic constructs, and
the well-being of the planet. As an
ecologist, I would love to see ecological data used sensibly in making
decisions about the environment.
Where things go wrong is when,
under the label of “environmentalist”, I am placed in the category of an
“interest group”, pitted against other
interest groups that are affected by
the recommendations I may make
over some impact to a habitat or any
other environmentally related issue.
A big part of the problem is that a
number of advocacy groups reside
under this label, together with often
well-intentioned people whose
actions and decisions have little
(and, in some cases, nothing at all)
to do with science or its conclusions.
There is a continuous, albeit tortuous, line between environmental
promotion, advocacy, politics, activism, and anarchy (including “ecoterrorism”), and the word “environmentalist” often gets thrown into
these categories.
An important role of ecologists is in
education – about how ecological data
are obtained, what they mean, and
how they can be used in implementing better resource protection and use
policies for the country. All too often,
these issues are heavily influenced by
dominant political and economic
interests, and it is already difficult
enough for ecologists to reach out to
politicians and decision makers with
sound advice. The labeling of ecologists as one more interest group in
these discussions (as so-called “environmentalists”) weakens our arguments and limits the benefits that the
science of ecology has to offer.
Carlos de la Rosa
Chief Conservation and Education
Officer, Catalina Island Conservancy,
Avalon, CA
(cdelarosa@catalinaconservancy.org)
The author responds
I greatly admire the work of Carlos
de la Rosa and the many other people who are dedicating their lives to
protecting our rapidly eroding environment. At the same time, it is
clear that ecologists are an interest
group, one with an explicit interest
in preserving the environment. We
apply objectivity, rationality, and
well-supported evidence in pursuit
of this goal. We are pitted against
other interest groups, and my editorial stressed that the most distinct of
our adversaries are those that harm
the environment. The label of
“environmentalist” is confusing only
to the degree that our adversaries
have succeeded in sullying the word.
I find no more continuous the line
of thought leading from “environmentalist” to “terrorist” than that
from physicist, chemist, physician,
Bayesian, and so forth, to this
hideous human behavior (“anarchy”
is for the libertarians and is the subject of another essay). That ecology
or any other science except cosmology operates without getting involved in the give-and-take of
human affairs is a notion for which
we can disabuse ourselves. Actually,
even cosmology these days is down
here dusting it up.
Donald R Strong
Department of Evolution and Ecology,
University of California, Davis, CA
(eicesa@ucdavis.edu)
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