Pest Risk Assessment for Introduced Forest Pests: Challenges Arising from Scientific Uncertainty

1
Pest Risk Assessment for Introduced Forest Pests
Challenges Arising from Scientific Uncertainty

• Faith Thompson Campbell, Ph.D.
• The Nature Conservancy, United States of America

My starting point protection of the ecological
integrity of natural systems. I will also
mention economic impacts. Neither type of impact
to natural system or to economic
interests/stakeholders is well documented.
Full documentation of ecological impacts might
not be possible because of complexity of forest
systems and gaps in our knowledge .
2
North America, Australia, and to a lesser extent
Europe and Asia have already suffered severe
impacts from introduced forest insects and
pathogens. In several cases, these introduced
organisms have nearly eliminated entire species
from the forest. Examples shown are Castanea
americana (chestnut blight), Cronartium ribicola
(white pine blister rust), Phytophthora cinnamomi
(ink disease), Ophistioma ulmi (elm disease),
Bursaphelenchus xylophilis (pinewood
nematode). Rising trade volumes raise the risk
unless effective measures are taken to prevent
such introductions. Values at risk include such
traditional agricultural ones as commerical
forestry forest products nursery production
and maple syrup and other forest products. Also
at risk are non-agricultural values, including
economic aesthetic values of our homes,
municipal private tree removal replacement
costs, nature-based tourism, and the ecological
values of natural forests.
3
One of the purposes of the international
phytosanitary system is to prevent repetitions of
these disasters. The system is manifestly
failing this test. Among the most prominent
introductions over the past 20 years are
Anoplophora glabripennis - Asian longhorned
beetle - North America Europe Agrilus
planipennis - Emerald ash borer in North
America Tetropium fuscum - brown spruce
longhorned beetle in North America Bursaphelenchus
xylophilis - pinewood nematode in
Europe Anoplophora chinensis - citrus longhorned
beetle in North America (eradicated)
Europe Phytophthora ramorum - sudden oak death in
Europe and North America Sirex noctilio -
woodwasp in North America Phytophthora kernoviae
- in UK Phoracantha recurva - in Africa Puccinia
psidii - ohia rust in Hawaii
4
IAS in natural systems are ecologically different
from agricultural pests4 illustrations of
differences

• In agriculture, plants pests have usually
  co-evolved so usually some resistance (and
  managers know about mitigation methods).
• When pathogens are introduced into natural
  ecosystems, and the pathogen and plant host have
  not co-evolved, there is usually limited genetic
  resistance to infection in host populations. Can
  be devastating results virtual elimination of
  tree species from the forest

D.M. Rizzo 2005. Exotic species and fungi
interactions with fungal, plant and animal
communities. pp. 857-877 in The Fungal Community,
edited by J Dighton, JF White, P. Oudemans. CRC
Press
5

2) Impacts of introduced forest insects and
diseases are cumulative long-lasting, with
cascading effects 3) Control options are limited,
drastic of limited efficacy exacerbated by
tardy detections 4) Management options can have
severe ecological impacts Post-introduction
response is costly, as is illustrated by the
U.S. experience with five forest pests - 50
million in one year, and that falls far short of
the need. Nearly 400 forest pests are not under
official control and that failure to act has
consequences.
6
The key dilemma in international trade agreements
can be summarized as follows
The potential magnitude of impacts lack of
effective mitigation measures, combined with
practical limits on the number of post-entry
eradication programs any country can carry out
Point to establishing a very high Level of
Protection appropriately stringent
phytosanitary measures However, the higher the
level of protection and more stringent the
measures, the greater the specificity probably
required in PRA. In evaluating a pathway, how
specific can scientists be in defining which
pests might be introduced, how likely such an
introduction might be, and how effective SPS
measures will be in preventing introductions?
7
How specific PRAs must be Key rulings of the
WTO Appellate Body
European beef hormone case (AB-1997-4) PRA must
evaluate the carcinogenic potential of specific
hormones at the specific residue levels that
would be found in specifically, 'meat or meat
products,' when the hormones are used
specifically for growth promotion purposes
italics in original Australia/Salmon case
(AB-1998-5) PRA must (1) Identify the hazards
and possible biological and economic consequences
of their entry or spread, (2) Evaluate the
likelihood of entry, establishment, or spread,
and (3) Evaluate the impact of SPS measures on
the likelihood of entry, establishment, or spread
of the hazards.
8
Japan-Apples (AB-2003-4)

• To defend any claim that a measure is intended to
  protect against illegal shipments, document that
  illegal shipments have occurred or are likely
• If adopting a systems approach, analyze the
  individual efficacy of each component and defend
  the need to impose the entire system.
• Analyze alternative approaches, not justify a
  pre-determined approach.

9
Provisional measures (under Art. 5.7) may be
adopted only in certain, restricted,
circumstances - Japan-Apples

• AB 1998-8 - must actively seek the missing
  information and review the provisional measure
  within a reasonable period
• AB-2003-4 - not allowed when there is sufficient
  information to complete a PRA that is, to
  evaluate the likelihood of entry, establishment
  or spread of the pest in question.
• unknowns do not equal insufficient
  information
• Issue not clarified
• Whether the PRA must be country-specific

10
Conducting a Pathway PRA does not solve the
problems arising from demands for specificity -

• Per Japan-Apples (AB-2003-4) and the proposed new
  IPPC ISPM 2 (Steward Draft Version), a pathway
  PRA must still attribute a specific likelihood of
  entry, establishment or spread to each pest
  evaluated.

11
NAPPO Concept Paper - Plants for Planting
http//www.nappo.org/Standards/Consultation/RSPM2
4-ConceptPaper3-8-04-e.pdf

• Documents that PRAs based on lists of known
  quarantine pests (as most are) do not address
  numerous uncertainties
• - many potential quarantine pest are obscure or
  unknown
• - pathogens are often poorly understood
• pest impact on host and non-host plants is poorly
  understood
• pest impact in native environment is an
  unreliable indicator of its behavior in a new
  ecosystem
• potential for genetic change or variability in
  pests or hosts
• - uncertain origins of the material or mother
  stock

12
Unknowns potential pests

• The number of arthropods extant globally is
  unknown estimates range from a few million to
  ten million
• Experts estimate that 95 of fungal species
  remain undescribed
• understudied fungal habitats include soil,
  leaves, roots the tropics
• Native ranges are unknown for many
• Examples of forest pathogens for which the area
  of origin was unknown when it was introduced
• Cryphonectria parasitica
• Ophiostoma ulmi O.novo-ulmi
• Phytophthora lateralis
• Discula destructiva
• Phytophthora cinnamomi
• Phytophthora ramorum
• Sirococcus clavigignenti-juglandacearum
• Phytophthora kernoviae

13
Weaknesses of Predictions

• There are currently no known broad scientific
  principles or reliable procedures for identifying
  the invasive potential of plants, plant pests, or
  biological control agents in new geographic
  ranges.
• National Research Council, Predicting Invasions
  of Non-indigenous Plants and Plant Pests 9
  (2002), available at http//www.nap.edu/books/030
  9082641/html/
• We do not believe that pest risk assessments can
  adequately identify organisms which may cause
  severe damage in North America.
• George C. Carroll, President, Mycological Society
  of America 1998. Letter to Dan Glickman,
  Secretary of Agriculture.
• Only 18 of insects and mites introduced in the
  U.S. behaved as expected
• W.E. Wallner, 2004. Assessing Exotic Threats to
  Forest Resources. In K.O. Britton, Editor.
  Biopollution An Emerging Global Menace. APS
  Press

14
Evolution Hybridization

• Risk of hybridization more widespread than
  appreciated - a general biological phenomenon.
• Can be quite rapid
• Facilitated by trade, which brings geographically
  isolated but related organisms into proximity
• Examples
• - Ophiostoma ulmi O. novo-ulmi
• - Phytopthora alni
• - Melampsora
• Clive Brasier (world expert on pathogens) has
  been warning about this risk for a decade

15
Complexity of Receiving Systems

• . . . forest ecosystems are highly complex, and
  most forest pests are not thoroughly understood.
  As a result, the answers to the key questions1
  often represent little more than speculation
• W.E. Wallner, 2004. Assessing Exotic Threats to
  Forest Resources. In K.O. Britton, Editor.
  Biopollution An Emerging Global Menace. APS
  Press
• 1These key questions are
• 1) What is the probability that the introduced
  species will be harmful?
• 2) How harmful is the introduced species likely
  to be?

16
Quantifying Impacts

• Quantifying the impacts of exotic species is
  often impossible or difficult because of a lack
  of baseline ecological data on invaded
  ecosystems. complexity of impacts affecting
  different spatial and temporal scales.
  individuals, populations, communities and
  ecosystems. Interactions may be positive,
  negative or neutral. cumulative and indirect
  effects / a cascade of changes throughout an
  ecosystem.
• Rizzo DM. 2005. Exotic species and fungi
  interactions with fungal, plant and animal
  communities. pp. 857-877 in The Fungal Community,
  edited by J Dighton, JF White, P. Oudemans. CRC
  Press

17
Lack of economic valuation methods for
non-commercial forest values Chornesky,
Bartuska, Aplet, Britton, Cummings-Carlton,
Davis, Eskow, Gordon, Gottschalk, Haack, Hansen,
Mack, Rahel, Shannon, Wainger, Wigley. Science
Priorities for Reducing the Threat of Invasive
Species to Sustainable Forestry Bioscience April
2005 Vol. 55 No. 4
18
Recommendations

• Allow pathway PRA to support pathway regulations
  that apply to all potential IAS using the
  pathway, not just those analyzed individually
• could be hundreds or even thousands of species
  using the pathway no country has sufficient
  resources to do the numerous catch-up PRAs that
  would be required to apply the pathway measure to
  each new pest as a provisional measure under
  Article 5.7
• Allow countries adopting policies aimed at
  countering newly recognized risks to the
  environment (as distinct from agriculture) to
  utilize provisional measures under Article 5.7 -
  so can close off these pathways promptly. The
  risk level is simply too high to delay.