Figure 1. An overview of KISC's efforts (represented in red) relative to a species' stage of establishment.
KISC’s Plant Early Detection Program is the only program that focuses on species that can be eradicated from the entire island of Kauaʻi. This is accomplished by identifying invasive plants that have not yet spread from cultivation, detecting plants in nurseries before they are distributed through sale, and by detecting naturalized populations that have not surpassed the eradication phase (Figure 1).
Kauaʻi is thought to include approximately 720 alien plants that have naturalized from over 2700 recorded in cultivation. A large proportion of these plants are deemed “High Risk” by the Hawaiʻi-Pacific Weed Risk Assessment (HPWRA), and our knowledge of important invasive species distributions is sporadic and incomplete. Thus, thorough early detection surveys readily produce a long, ineffective list of potentially incipient taxa that are clearly displaying invasive behavior or are considered “High Risk”. A systematic process to prioritize eradicable species with the largest invasive impact potential is necessary because the relatively small capacity of KISC is incapable of controlling all species detected.
Figure 3. The importance of taxonomic, ecological and geospatial data in alien species-rich management areas
3.a) Creating a Survey List
The 2015-2017 Survey List consisted of 176 potentially invasive species with limited or unknown distributions. This list was originally limited to 134 species to prevent surveyor error, but 42 more taxa of interest were added when previously unknown or newly naturalized species were encountered in the field or recommended by partners/specialists.
How We Did It:
The Survey List was created using a data informatics strategy by amassing three types of data (taxonomic, ecological and geospatial) into a provisional Kauaʻi Alien Plant Database for reasons outlined in Figure 3.
A species inventory was compiled using digitized herbaria data and previous early detection data and cross referenced with the Kauaʻi Alien Plant Database to: 1) list potentially invasive species, and 2) eliminate species with broad distributions.
3.b) Island-Wide Surveys
2015-2017 surveys covered a total of 3496 ha (8640 acres) of Kauaʻi (Figure 4) with 2447 GPS points taken to denote plants of interest or unknown plants. This includes:
- all publicly accessible roads, accounting for 2306 ha (5698 acres) of area and 79.59% or 778 kms (483 miles) of roads.
- 287 kms (178 miles) of hiking trails, including 30 separate trails.
- 15 high-risk sites, including 6 nurseries, amounting to 91 ha (226 acres).
- 342 ha (846 acres) of aerial surveys, and
- 630ha (1558 acres) of boat surveys.
Figure 4: Island-wide survey effort by the KISC early detection botanist from August 2015 – November 2017.
Two hundred and ninety-four herbarium vouchers, amounting to 642 separate specimens (including duplicates) were collected, identified and are currently being submitted to herbaria. An additional 80 vouchers still await identification before submission to herbaria.
How We Did It:
Plants of interest were mapped using a GPS/photographs, and notes on size, structure and maturity of populations were taken. All unknown plants encountered in the field were recorded. Vouchers of alien species including new island records and important range extensions were collected to ensure accurate taxonomic identifications and to contribute to a basic, long-term understanding of Kauaʻi’s flora.
Table 1. Sixteen species that KISC will further investigate as potential Target or Partnership species (table simplified from 2015-2017 KISC Plant Early Detection Report).
The full prioritization table can be viewed here.
Forty-two species received prioritization assessments. These species were ranked in order according to a priority score, which reflects an additive value of eradication feasibility and potential invasive impacts.
KISC will begin investigation of all species with a ranking between 1-10, in the order they are ranked. This includes 16 species total: 4 potential Partnership Species), 11 potential KISC Targets, and 1 Rapid Response species.
How We Did It:
Figure 5. An excerpt from the Prioritization Assessment report for Bishofia javanica (bishop wood). These reports produce scores that are then ranked among other species to determine the order of eradication priority for KISC.
A semi-quantitative method for assessing the magnitude of potential impacts and feasibility of eradication for incipient alien species was developed in 2015. This process results in a comparative prioritization tool allowing allocation of resources to the highest-ranked species, allowing KISC to designate certain “Early Detection” species as a KISC “Target” (Figure 2).
Step 1: Research Species and Locality Background
Step 2: Assess Detection and Distribution
Step 3: Mine Hawaii-Pacific Weed Risk Assessment Responses
Figure 6. A visualization of how individual species are scored and ranked as part of KISC's Prioritization Process (Figure 2).
5.a) Recommending Species to Phase Out of Local Nurseries
Figure 7. Molineria capitulata (weevil lily), a commonly sold herb on Kauai, forming the dominant herb layer in Hāʻena State Park.
KISC launched the Pono Endorsement Program in 2016, which provides lists of species that should be discontinued from sale in businesses holding a Pono Endorsement. A major challenge in compiling these lists is that no inventories of nursery stock have been completed, and businesses frequently change which plants they order and propagate for sale. The absence of these data may increase the risk that the phase out list contains invasive plants that are no longer cultivated, rendering the list ineffective. Field surveys documented invasive impacts of plants sold in nurseries on Kauaʻi, allowing KISC to better select candidates for the phase out list.
Fourteen species were recommended for the future Pono Endorsement “phase out” list, which met two criteria: 1) found in nurseries during 2015-2017 surveys and 2) surveys recorded potential environmental, agricultural or cultural impacts.
5.b) Reporting New Naturalization Records
Figure 8. Euphorbia tithymaloides (devil's backbone) naturalizing and invading a coastal ecosystem on Kauai.
Number of Taxa*
|New State Naturalization||7|
|New Island Naturalization||29|
|Showing Early Signs of Naturalization||13|
|Previous Record Amendment (ID error)||1|
|Demotion from Nat to Nat? - Potentially Eradicated||3|
|TOTAL RECORD CONTRIBUTION||53|
|Future records awaiting voucher collection (observed but not collected)||12|
5.c) Reporting Out-of-Scope Species
Figure 9. A map showing widespread distribution of cultivated and non-cultivated occurrences of Pittosporum pentandrum- a species that is likely infeasible to eradicate by KISC.
Background and distribution data for 61 species of interest that did not recieve Prioritization Assessments were compiled, including 37 taxa that were found to be too widespread to eradicate. This report will be used to 1) revisit eradication feasibilty if additional funds, partnerships or information is acquired, 2) prevent future KISC staff from re-evaluating taxa that have already been assessed, and 3) supplement KISC's knowledge for outreach and partnership purposes.
5.d) Tracking Signs of Invasive Impacts
Figure 10. Xyris complanata (yellow-eye grass; yellow flowers, reddish-brown stems) replacing native graminoids in a high-elevation bog ecosystem.
Many invasive plant management programs depend on invasive impact (harm) data from outside of Hawaiʻi to inform management decisions, although few document invasive impacts within the state. 2015-2017 surveys reported dense, invasive populations that are likely causing impacts for 16 species that are beyond eradication but have not spread across their entire potential range.
1) The Prioritization Process implemented by KISC resulted in a comparative data table that identified multiple specific management strategies that may be pursued, depending on focus, funding sources and partnerships.
A) Focus on a hotspot of prioritized species (10 spp.) located in the high elevation, high-value native habitat around Kokeʻe. This hotspot likely reflects Kokeʻe as the only human settlement on Kauaʻi with a temperate climate, and thus, many invasive species in the area were not planted elsewhere on the island.
B) Focus on species (6 spp.) that have the potential to damage coastal ecosystems. The high number of still-eradicable species prioritized may reflect that few alien species can tolerate the wind shear and saline conditions of these sites.
C) Focus on species that may impact agricultural resources (8 spp.)
D) Focus on "low-hanging fruit" (species with high feasibility scores, but a wide range of invasive impacts scores; 7 spp.)
E) Form partnerships to tackle High-impact / Low feasibility score species (7 spp.)
2) Detection and control feasibility on private land remains a major challenge. Issues with landowner cooperation have already been uncovered for 15 of the 42 species assessed.
3) Training, funding and safety issues must be tackled to address control of large tree species, which often have high invasive impact scores but low feasibility scores.
4) Lack of Hawaiʻi-specific data cripples our ability to assign potential invasive impact scores. 12 out of 42 of the assessed species show potential or confirmed invasive behavior in Hawaiʻi that has been reported nowhere else in the world.
5) Language to describe signs of invasive behavior and stages of naturalization is variable in Hawaiʻi, making it hard to use data from other islands.
6) Lack of identification resources affects our ability to score and rank plants. The identity of 3 of 42 species assessed (+ 7 other species of interest) remain uncertain.