Ecological, economic and social considerations of spray control for Hymenachne

Citation

Land & Water Australia. 2008. Ecological, economic and social considerations of spray control for Hymenachne. [Online] (Updated April 28th, 2009)
Available at: http://lwa.gov.au/node/2589 [Accessed Tuesday 12th of March 2013 02:31:02 PM ].

Summary

Hymenachne, a Weed of National Significance (WONs), is an aquatic plant invading northern Australia’s wetlands and waterways. The proliferation of this weed is associated with serious ecological losses and there are substantial costs associated with its control. Hymenachne also deserves special attention given the nexus regarding its beneficial use as a ponded pasture species for livestock production and drought management, and the disadvantages associated with its spread and ecological impact. A key challenge in the management of this weed is to understand the best ways to approach Hymenachne control, whilst satisfying environmental, social and economic concerns.

This study used a triple bottom line approach to improving the understanding of the issues facing Hymenachne control. This involved the integration of the social, economic and ecological studies and ecological surveys conducted in conjunction with a sample spray regime.

Aims

Project objectives:

1. A detailed review of literature will report on issues including, but not limited to, the current spread of Hymenachne, existing methods for control, available data on ecological consequences of spray regimes and the socio-economic impacts of the weed and different control measures.

2. The ecological component of the study will address the following research questions:

(a) What are the adverse ecological impacts associated with chemical spray regimes (e.g., decline in water quality, changes to aquatic habitats, loss in vertebrate & invertebrate biodiversity)?

(b) What is the extent of system recovery in the short term, following spray and/or successful hymenachne control (possibly including recolonisation by native vegetation)?

3. The key research questions for the economics component relate to the knowledge, barriers and incentives that will generate participation in control strategies:

Quantifying the economic costs of control and the level of incentives needed to generate effective participation
on-farm economic losses due to lost production where Hymenachne is removed from ponded pastures
costs of control measures
types and levels of incentives needed to encourage on-farm control activities,
the structure of incentive mechanisms needed to generate sufficient participation by landholders at a landscape scale.

4. The investigation of broader social issues regarding Hymenachne will include questions such as:

What is the current level of awareness & perceptions of the Hymenachne problem in central Queensland by landholders?
What is the extent of willingness to participate in control programs?
What barriers, catalysts and enablers influence landholder adoption of, and/or cooperation with, Hymenachne control regimes?
An analysis of conflicts of interest existing in regards to Hymenachne as (a) a ponded pasture grass used for livestock production and (b) an ecologically destructive weed of national significance
Investigations of strategies that could be put in place to foster greater awareness of the weed problem, cooperation across stakeholder groups and a wider adoption of control

Outcomes

Key findings were the need for a coordinated and inclusive approach to Hymenachne control across all stakeholders and landholders, with suitable incentives being made available and responsibility taken for control by each of the Government, Councils and the community. With respect to chemical control spraying, there was little evidence that this causes long-term, significantly negative effects on freshwater systems with respect to water quality, pesticides residuals, and biota (macroinvertebrates, fish and semi-aquatic invertebrates). This contrasts with the known adverse ecological effects of dense Hymenachne cover demonstrated in earlier studies, thus suggesting that control sprays should be employed to reduce existing infestations and prevent new outbreaks.

Background

Hymenachne, a Weed of National Significance, is an aquatic pest plant that is invading northern Australian wetlands and waterways. Its proliferation is associated with serious ecological issues and there are substantial costs associated with its control. However, Hymenachne is also valued by some livestock producers as a ponded pasture important in drought management.

A significant challenge for the control of Hymenachne is to balance the economic, social and environmental costs and benefits of its use and management.