Cost of invasives Fiji

December 2012. A message from Landcare Research, New Zealand. A survey has been carried out that collected detailed information on the economic and biophysical impacts of five key invasives from more than 470 households in 40 villages in Eastern Viti Levu and Taveuni, Fiji. The survey, which was funded by the Critical Ecosystem Partnership Fund, also identified a list of interventions that the various communities are taking at the village level to mitigate some of the impacts. The five species are:

We are now in the process of conducting formal cost-benefit analysis of impacts and control of these invasives at the village scale in Fiji. To adequately estimate the costs and benefits of the various management methods, we still need more information on the key physical data for these species. The largest data gaps include:

1. The biological growth and spread of the different invasive species. For example, we know that the African tulip tree follows a logistical growth curve and would reach a certain carrying capacity of X trees/ha, but we have yet to find a study that provides some estimated values to use to parameterise the function.

2. Effectiveness of methods to manage specific invasive species (pesticides, herbicides, manual labour, machine/capital intensive methods, etc.). For example, we know that applying some herbicides can have an impact on the African tulip tree, but we have still not been able to find a study that explicitly lists the average level of effectiveness for various application rates.

Thus, we are asking you to help by sending us information peer-reviewed publications, reports, policy briefs, theses, etc. that could help us estimate these physical functions.

A lot of the benefits of invasive species management will be accrued in the future, so it is very important that the economic analysis has the best possible information on the biological growth and management functions for these species that are based on the scientific literature.

In answer to the questions, a member from Tahiti wrote:

A study conducted by one of my graduate student in a lowland (at ca. 200 masl) rainforest (mean annual rainfall between 1600-2000 mm per year) of the tropical island of Tahiti, Society Is. French Polynesia (see her report -in French- http://www.li-an.fr/jyves/Laitame_2010_Rapport_stage_Impact_cyclone_foret_Tahiti.pdf) shows that Spathodea campanulata large trees (dbh >20 cm) density reaches 271 individuals per hectare, with a basal area for all plants (height >1.3 m) of 38.74 m²/ha, based on a 1400 m² study plot.

African tulip tree is found in Tahiti up to 1100-1200 m elevation in cloud-forest (see http://li-an.fr/jyves/Meyer_et_al._2008_Guide_Plantes_Envahissantes_Polynesie.pdf), but its abundance decreases with altitude as shown by another study of another graduate student of mine conducted on several permanent plots set up in the island of Moorea, Society Is. (http://www.li-an.fr/jyves/Fraisse_2010_Rapport_Stage_Master_Moorea.pdf).

Another member commented that would have thought that the two species of Myna present in Fiji Acridotheres tristisand Acridotheres fuscuswould have rated higher than Bulbul, both from agricultural and biodiversity point of view.

Some survey work in Fiji a few years ago indicated that they comprise 83% of the bird population in Fiji.

Members were reminded of a previous discussion on Pestnet concerning the tulip tree as a pest: Pests/Pestoutbreaks/Invasivepests/WhatmakesapestinvasiveSamoa

The information contained in the original post has been put on Ecoport, with some additional data: http://ecoport.org/ep?SearchType=interactiveTableView&itableId=84668