# Presentation: 026284

## Weed Risk Assessment- A Tool for Selecting Non-Invasive Species for Forestry, Gardening and Landscaping in Hawaii

- Curt Daehler, UH Department of Botany
- Duane Nelson, Forest Health Coordinator
- Julie Denslow, Ecologist and Team Leader
- USDA- Forest Service, Institute of Pacific Island Forestry

**Notes:**
Invasive alien plants pose one of the major threats to biodiversity on Pacific Islands. Unfortunately some of these species were established as intentional introductions for reforestation, windbreaks, landscaping or watershed protection. Some unfortunate introductions include melochia, silk oak, Faya tree, black wattle, blackwood acacia, Mexican weeping pine, ironwood and Miconia.  Though these species may have provided some benefits, they have unarguably become weeds that impose huge costs to landowners, and society. 
The intent is not to denigrate decisions made by our forbearers, but to help avoid bad decisions now and in the future.
Exotic tree species have become the foundation for forestry on Pacific islands.  Despite growing interest in native species, ease of establishment, rapid growth, high stumpage value, disease resistance, novelty and suitability for plantation forestry continue to entice foresters to plant exotic species for many purposes. 

## Needs: Decision tools for making responsible planting choices 

-  Develop and test a weed risk assessment (WRA) system that identifies plants likely to become invasive pests
- in Hawai‘i.

-  objective
-  transparent
-  science-based
-  repeatable
-  reliable

- Needs: Decision tools for making responsible planting choices

**Goal:**

**Characteristics of an ideal WRA system**

## Uses of the WRA system in Hawai‘i

-  allow informed planting decisions
- 	nursery growers, architects, landscapers
- 	foresters, land managers, ranchers
- 	public
-  assist in prioritizing proactive control efforts

-  assist with import decisions

- Species not yet in Hawai‘i

- Species already in Hawai‘i

## Developing the WRA system for Hawai‘i

-  The Australian AQIS system was most promising after simple modifications1

**1994**  Developed and tested in Australia
**1995**  Modified and tested in New Zealand
- (currently used in both countries)

-  Several systems were examined for use in Hawai‘i

- History of the Australian WRA system

- 1Daehler and Carino 2000

**1998** Modified and tested for use in Hawai‘i
**2001-2002**  Further testing for use in Hawai‘i 	       and other Pacific Islands

##  climate/distribution

** ****domestication**
** ****weed elsewhere**
** ****undesirable traits**
** ****plant type**
** ****reproduction**
** ****dispersal**
** ****persistence attributes**

**Score**

**< 1****	****not a pest**
**1-6    evaluate**
**> 6****	****pest**

- Australia/New Zealand
- Weed Risk Assessment System

- 49 questions

**Prediction**

##  Designed to identify all types of pest plants

- Weed Risk Assessment System

-  Designed to identify all types of pest plants

- -- invaders of natural areas
- -- weeds of agriculture and forestry
- -- nuisance species

-  Don’t need to answer all 49 questions
-  Assessment can be done quickly (within a day)

## Example: WRA for Miconia calvescens

- Example: WRA for *Miconia calvescens*

- Score: 14
- Decision: PEST

-  Environmental weed of Tahiti
-  Broad range (0-6000 ft elevation)
-  Shade-tolerance
-   Re-growth after mutilation

- Risk factors

## Example: WRA for Miconia calvescens

- Example: WRA for *Miconia calvescens*

- Score: 14
- Decision: PEST

-  Self-compatible
-  > 1000 seeds per m2
-  Bird-dispersed
-  Easy accidental dispersal by humans

- Risk factors

## WRA Score: -5

- WRA Score: -5
- Decision: NOT A PEST

- Risk factors

-  toxic/allergenic sap
-  tolerates a wide range of soil conditions

- Risk reducing factors

-  not a recognized pest elsewhere

## WRA Score: -5

- WRA Score: -5
- Decision: NOT A PEST

- Risk-reducing factors

-  not a recognized pest elsewhere
-  poor shade tolerance
-  does not form dense thickets
-  specialist pollinator
-  lacking natural vegetative spread

## Further assessment of the EVALUATE category

- (species scoring between 1 and 6)

-  Based on scientific literature, we applied simple decision rules

-  About 25% of species scored between 1 and 6

## Evaluating the WRA system decisions in Hawai‘i

- December 2001 - June 2002
-   200 plants were evaluated using the WRA system
-  most species were found on planting lists in Hawai‘i
-  each WRA question was answered in a consistent manner
-  information from around the world, including Hawai‘I
- scientific literature, horticultural literature, Internet databases
-  sources for all information were documented

- Species were classified as:
- 	Not a pest (WRA score <1)
- 	Pest (WRA score >6)
- 	Evaluate (WRA score 1-6)

- second
- screen

- Not a pest

- Pest

## Evaluating the WRA system decisions in Hawai‘i

-  Compared WRA decisions with 18 expert opinions

-  botanists/weed scientists
-  first hand, detailed knowledge of weeds in Hawai‘i
-  native ecosystems
-  managed ecosystems

- The expert evaluators:

## Questions to Evaluators

- 1. 	Is it present in the region?
- 2.  Is it naturalized in disturbed habitats?
- For native/managed ecosystems:
- 3. 	Is it currently naturalized?
- 4. 	What is its current status ?
- 		not a pest
- 		minor pest
- 		major pest
- 5. 	What is the estimated future status?
- 		not likely to become a pest
- 		minor pest
- 		major pest

## Evaluating the WRA system decisions in Hawai‘i

- All species were classified based on the expert surveys

- Major pest  --    at least 3 experts agreed
- Minor pest --     at least 3 experts agreed
- Not a pest --     all other species

-  individual opinions varied (differences in personal experience)

**Classification criteria**

## Results: species with an NON-PEST WRA rating

- (108 of 178 species assessed)

- 86% Agreement between WRA and experts

- NON-PEST rating

- ‘major’

## Examples

- Non-pests according to WRA (experts agreed)

*Bougainvillea glabra*	paperflower		-1
*Breynia disticha*		snow bush		-5
*Cassia xnealiae* 		rainbow shower	-8
*Citrus limon*			lemon			-3
*Cordia sebestena*		geiger tree		-1
*Erythrina variegata*		coral tree		-2
*Fagraea berteroana**	*	pua keni keni		-1
*Galphimia gracilis*		slender goldshower	-2
*Graptophyllum pictum*	caricature-plant	-5
*Guaiacum officinale**	*	lignum vitae		-6
*Heliconia caribaea*		lobster claw		-1
*Lagerstroemia speciosa*	queen's crape myrtle-4
*Petrea volubilis*                   sandpaper vine	-1

- Score

## Examples - - “mistakes”

*Fraxinus uhdei*			tropical ash		0
*Tournefortia argentea*		tree heliotrope	-1

**Examples - - “mistakes”**

*Cryptomeria japonica**	**	*Japanese cedar	-3*	*
*Filicium decipiens**	**	**	*fern tree*	**	*-3
*Senna surattensis**	**	**	*kolomona		0*	*
*Zingiber zerumbet **	**	**	*shampoo ginger	-1
*Zoysia tenifolia**	**	**	*templegrass		-2

- Experts rated as MAJOR pests (only 2 “mistakes”)

- Experts rated as MINOR pests (13 “mistakes” total)

- Non-pests according to WRA  BUT:

- Score

## Results: species with a PEST rating

- (56 of 178 species assessed)

- 80% Agreement between WRA and experts

- PEST rating

- 11 reject “mistakes”
- (among 178 total evaluations)

## Examples

*Bischofia javanica*          	bishopwood       	 7
*Elaeagnus umbellata*	autumn olive		13
*Pittosporum undulatum*	Aust. cheesewood	9
*Tamarix aphylla*		Athel tamarisk		13

- High WRA score but not pests according to experts

**Examples**

- High WRA score and major pests according to experts

*Ardisia elliptica*                   shoebutton ardisia	11
*Brachiaria mutica*		para grass 		12
*Citharexylum spinosum*      fiddlewood		7
*Coccinia grandis*   		ivy gourd		21
*Psidium cattleianum*   	strawberry guava	18
*Pyracantha angustifolia*      narrowleaf firethorn	13

- Score

- “Mistakes”

## Results summary

-  The WRA ratings were 80-86% consistent with assessments made by a large group of plant experts

-  If the WRA system were used for import and planting decisions, Hawai‘i’s invasive plant problems could be greatly reduced

-  The WRA ratings screened out 95% of the major pests
-  The WRA accepted 84% of non-pests

## Things to remember

-  Any risk assessment system can make occasional mistakes (the same is true of “experts”)
-  But, compared to individual expert opinions, WRA ratings are less variable and less subjective1

- 1also demonstrated in Australia and New Zealand

## Things to remember

-  If used for planting decisions, WRA ratings can greatly reduce invasive plant problems
-  WRA ratings currently have no legal standing; industry has an opportunity to take the lead

## Future directions:

-  Screen more species

-  proposed imports
-  requests from industry, public?
-  commonly used planting lists
-  develop a long list of low risk/ non-invasive plants
-  expert review of WRA’s to minimize errors?

## Future directions:

- Outreach

-  increase awareness of invasive plant problems
-  publicize assessment results
-  identify and promote lower risk alternatives to “rejected” species
-  “Green certification”?