M.J.B. Dyer, G. Keppel, D. Watling, M. Tuiwawa, S. Vido and H.J. Boehmer Dyer, M.J.B.; G. Keppel, D. Watling, M. Tuiwawa, S. Vido and H.J. Boehmer. Using expert knowledge and fi eld surveys to guide management of an invasive alien palm in a Pacifi c Island lowland rainforest Using expert knowledge and fi eld surveys to guide management of an invasive alien palm in a Pacifi c Island lowland rainforest M.J.B. Dyer1, G. Keppel1,2, D. Watling3, M. Tuiwawa4, S. Vido5 and H.J. Boehmer6,7 1School of Natural and Built Environments and Barbara Hardy Institute, University of South Australia, Mawson Lakes Campus, GPO Box 2471, Adelaide, SA 5001, Australia. <[email protected]>. 2Biodiversity, Macroecology and Conservation Biogeography Group, Faculty of Forest Sciences and Forest Ecology, University of Goettingen, Göttingen, Germany. 3Environment Consulting Fiji, Suva, Fiji. 4South Pacifi c Regional Herbarium, Faculty of Science, Technology and Environment, University of the South Pacifi c, Suva, Fiji. 5Forestry Department, Ministry of Fisheries and Forests, Suva, Fiji. 6School of Geography, Earth Science and Environment, Faculty of Science, Technology and Environment, University of the South Pacifi c, Suva, Fiji. 7Institute for Applied Ecological Studies (IFANOS), Baerenschanzstrasse 73, Nuremberg, Germany. Abstract Invasive alien ornamental plants are a global problem, especially on oceanic islands, and can have severe impacts on native biodiversity. Pinanga coronata, is an ornamental palm tree that can form mono-dominant stands in its native habitat and is widely cultivated throughout the tropics. Here we investigate the introduction, spread, impact and management of this invasive palm in the Fiji Islands, using extensive discussions with local experts and fi eld surveys. Pinanga coronata was introduced in the 1970s to the Colo-i-Suva area, eastern Viti Levu island, Fiji´s principal island, and has since become invasive in mahogany plantations and lowland rainforest. It has also been introduced and is becoming invasive on the western side of that island. However, the distribution of P. coronata remains geographically limited to the immediate vicinity of introduction sites but it is rapidly spreading. In each location, the species has formed mono-dominant stands in the understorey and appears to be displacing native plant species, as suggested by a negative correlation of its abundance with that of native tree ferns. This highlights the need for rapid control of P. coronata in Fiji. Local experts state management should involve manual removal of seedlings and saplings, killing of adult palms by injection of herbicide, and education and legislation to prevent the further spread of the species. Based on these recommendations and fi eld data, management actions to control P. coronata are proposed and steps to develop these into a management plan are discussed. Given P. coronata threatens native biodiversity in Fiji and has the potential to invade other rainforest ecosystems in the tropics, proposed management approaches are urgent and relevant for other tropical countries. Keywords: biodiversity loss, biological invasion, island biology, mahogany plantation, management plan, mono- dominant protected area, ornamental INTRODUCTION The tropical Pacifi c islands are highly vulnerable to general (Tye, 2009; Keppel, et al., 2012). However, local the impacts of invasive alien plant species because of the communities and experts often have extensive knowledge region’s geographic isolation and evolutionary traits that about their environment (Lefale, 2010; Keppel, 2014; leave species vulnerable to competition (Gurevitch & Keppel, et al., 2015). In Fiji, expert knowledge plays a Padilla, 2004; Denslow, et al., 2009; Caujapé-Castells, et crucial role in conservation and protected area management al., 2010; Woinarski, 2010; Minden, et al., 2010b). The (Keppel, 2014) and has provided important information region has the greatest rate of increase in the number of about the conservation status of rare trees (Keppel, et al., invasive alien plant introductions with respect to area in the 2015). world (Van Kleunen, et al., 2015). Furthermore, invasive Using results from a quantitative fi eld survey and species are a major cause of extinction on Pacifi c Islands qualitative expert knowledge, we demonstrate that P. (Tye, 2009). With increasing economic development in coronata is threatening biodiversity and displacing native nations of the Pacifi c, the diversity and impact of invasive tree ferns in lowland rainforests and mahogany plantations. plants in the region is likely to increase (Kueff er, et al., We then combine these two lines of evidence as the basis 2010). for a management framework to address the P. coronata Pinanga coronata, or ivory cane palm, is an ornamental invasion and its impact on native biodiversity in Fiji. palm tree that is cultivated and traded throughout the Acknowledging the current challenges in the Pacifi c for tropics (Palmpedia, 2017). The palm is native to lowland invasive species management (Tye, 2009), the framework rainforests in Java and Sumatra (Kimura & Simbolon, incorporates methods that are economically viable, 2002) and has been identifi ed as a potentially invasive develops capacity building and promotes awareness for all alien plant species on Pacifi c and other oceanic islands stakeholders related to the P. coronata invasion. (Meyer, et al., 2008). Introduced to Fiji in the 1970s for its ornamental properties, the palm has become invasive METHODS in lowland rainforest and mahogany plantations (Keppel & Watling, 2011) but the current extent of its distribution Site description is unknown. The Fiji Islands have a unique and highly The Fiji Islands include over 300 islands and islets in diverse biota that is severely threatened by habitat loss, the western South Pacifi c (Mueller-Dombois & Fosberg, exploitation, pollution and invasive species (Myers, et al., 1998). Fiji has a tropical climate with a wetter season 2000; Keppel, et al., 2014). from November to April and a drier season from May to Pacifi c small island developing states (SIDS) have October. Due to the south-east trade winds orographic limited information, funding and trained professionals rainfall produces higher precipitation in the south-east for invasive species management and conservation in of topographically more complex islands (Mataki, et al., In: C.R. Veitch, M.N. Clout, A.R. Martin, J.C. Russell and C.J. West (eds.) (2019). Island invasives: scaling 417 up to meet the challenge, pp. 417–423. Occasional Paper SSC no. 62. Gland, Switzerland: IUCN. Island invasives: scaling up to meet the challenge. Ch 2E Other taxa: Plants 2006). The capital of Fiji, Suva, is in the south-east of the (Keppel & Watling, 2011) and was fi rst recognised as a archipelago’s largest island, Viti Levu, and has an average potentially invasive species in 1992 (Watling & Chape, annual rainfall of about 3,000 mm and an average surface 1992). Since its introduction the palm has become dominant temperature of 25.4°C (Mataki, et al., 2006). in the understorey of mahogany plantations (Watling, 2005) and invasive in native lowland rainforest, forming The Colo-i-Suva area is approximately 12 km north of mono-dominant stands (mature palms and saplings) of Suva (Fig. 1) and has four protected areas. The Colo-i-Suva several metres in diameter (Keppel & Watling, 2011). Forest Park has no legal status but comprises the Colo-i- Suva Forest Reserve (FR; 370 ha) and the Maranisaqa- Wainiveiota FR (77 ha). Adjacent are the Savura FR (448 Interviews ha) and the Vago FR (24.7 ha). The area is mountainous Experts were consulted by the lead author through and the vegetation communities are fragmented, lowland informal discussions during fi eldwork, and in semi- rainforest and mahogany plantations amongst agricultural structured interviews in the offi ce from July to September and urban landscapes. The Savura and Vago FRs are mostly 2016, regarding the invasion history of P. coronata. comprised of lowland native rainforest with minimal Discussions were open ended but the key themes were the disturbance. These FRs constitute a major catchment for introduction history, distribution and dispersal, impact on the Savura Creek, which secures the water supply for the native fl ora and recommended management of P. coronata. capital city (Keppel, et al., 2005). Colo-i-Suva Forest Park is a mahogany plantation that has not been commercially Field survey logged since its establishment in the 1960s (Tuiwawa & Keppel, 2012). The Forest Park has conservation values A systematic fi eld survey was conducted in the Colo-i- because the mahogany plantations support a rich native Suva Forest Park and Savura FR. The aim was to identify understorey (Tuiwawa & Keppel, 2012), and is also areas of management priority and to determine if P. frequented for recreational activities including local and coronata is spreading. Using the Fishnet Tool in ArcMap international tourism (Malani, 2002). 10.2.2, a 300 x 300 m grid with 11 columns and 15 rows was overlaid on the boundaries of Colo-i-Suva Forest Park Study species and Savura FR. The centre point of each grid cell was imported into a Garmin Etrex 30® as waypoints. A 5 x 5 m Pinanga coronata, is native to western Indonesia, on plot was placed at each waypoint within the boundaries of Java and Sumatra where it is abundant in the rainforest the two forest reserves. understorey and occurs from sea-level to about 1800 m (Kimura & Simbolon, 2002). The species can be found The abundance of P. coronata was recorded in ninety- on steep hillsides, lowland fl ats and exposed ridges, and two 5 x 5 m plots in Colo-i-Suva Forest Park (54 plots) juvenile palms are found at higher densities on lower and Savura FR (38 plots). The abundance of the palm slopes and moist areas (Kimura & Simbolon, 2002). was determined as the number of mature (stem > 1 m in Tolerating low light conditions, P. coronata forms mono- height), juvenile (>0.5–<1.0 m) and seedling (< 0.5 m) dominant clusters in the rainforest understorey, where palms, calculated by counting their numbers in each plot.