Managing Ludwigia peruviana (L.) HaraH & Ludwigia longifolia (DC) HaraH infestations in NSW: Progress and Prospects Dr. Nimal Chandrasena GHD Pty Ltd
OUTLINE 1. The Invaders in Sydney and NSW, Australia 2. Magnitude of infestations 3. Focus on management- Case studies 4. Spread across NSW 5. Conclusions What we have learnt
Sydney Basin Hawksberry-Nepean River Botany Wetland Sydney Airport
Introducing the Invaders Ludwigia peruviana (L.) Hara (Primrose Willow) (= Jussiaea peruviana, J. grandiflora,, J. suffruticosa) Ludwigia longifolia (DC.) Hara (Long( Long-leaf Willow Primrose) ONAGRACEAE Native area- Central America Pan-tropical, 0-14500 m altitude (Indonesia, Sri Lanka) In the Sydney basin- (30 0 South latitude) L. peruviana- in 1971 (escape from Botanic Gardens) L. longifolia- In 1991 (escape from Nurseries?)
Botany Wetlands- Sydney Water Water supply, Sydney 1850-1866 59 59 Ha Ha wetlands, 11 11 ponds ponds + land land 4 Km, Km, eastern suburbs, open open to to the the Botany bay bay Flood-mitigation system Largest freshwater lakes lakes
Botany Wetlands- Sydney 1996 o Highly valued (native vegetation, wildlife habitats, aesthetic) o Degraded by aquatic weeds (Ludwigia peruviana, Alligator Weed, Salvinia, Water Hyacinth) and Invasive trees (Willows, Coral trees)
Botany Wetlands- Pond 3 P 5 P 3 Pond Pond 3 (75% (75% cover cover of of L.p) L.p) Invasive Willows, Coral Coral trees trees
Ludwigia peruviana in Sydney 2.5 m
Botany Wetlands- Pond 1 Pond Pond 1 (90% (90% cover cover of of L.p) L.p) Invasive Willows, Coral Coral trees trees P 1 P 2
Botany Wetlands- Pond 1A Willow grove Pond Pond 1A 1A (90% (90% cover cover of of L.p) L.p) Invasive Willows
Ludwigia peruviana- potential distribution
Integrated Weed Management
Integrated Weed Management Revegetation- Assisted regeneration Purposeful planting of native species Tansplanting macrophytes Bush regeneration Habitat creation- logs, snags
Botany Wetlands, Sydney Before (up to 1996) After (2006) Serious noxious weeds Poor water quality, murky water Stagnant water due to choking Toxic algal blooms annually, Feral fish (European Carp) Poor diversity of native plants Less noxious weeds, invasive trees better water quality, water clarity (>3.0 m) Vastly improved flow No algal blooms, reduced feral fish Native plants- greater diversity
Botany Wetlands, Sydney Pond 1A After (2006) 1 frog species; 99 bird species (1991) Before (up to 1996) 6 frog species; 164 bird species (2004)
Botany Wetlands, Sydney L. peruviana- negligible Native vegetation (Typha orientalis, three Baumea sp., Phragmites australis, Juncus sp., Cyperus sp., Schoenoplectus sp., Elaeocharis sp. + many others) % Area 80 70 60 50 40 30 20 10 0 Vegetation Changes- Botany Wetlands Ludw igia Undesirable Vegetation Native Vegetation Open Water 1996 1998 2000 2002 2005
Botany Wetlands- Annual costs of implementing IWM and monitoring Ecological Health 400 350 Annual Costs of Implementing IWM- Botany Wetlands Total costs IWM- on ground costs Management costs Monitoring Review Aus $ '000 300 250 200 150 100 New POM 50 0 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 Annual Monitoring- WQ, Macroinvertebrates, Frogs, Reptiles, Ausrivas SIGNAL Index, Vegetation Birds- once in 5 years
Ludwigia longifolia- north of Sydney (Newcastle) Location of Mambo Wetlands (175 ha), Salamander Bay, Port Stephens, Largest infestations of L. longifolia- first found Note closeness to the port city Newcastle, north of Sydney. Other infestations, thus far are small and sporadic in occurrence.
Ludwigia longifolia L. l found in Botany Wetlands in 1991, 2002, 2005; Just upstream of drain is a nursery Controlled with herbicides + manual removal Persistent seeds
L. peruviana has spread widely over the past 12 years, despite implementation of Regional WMP L. longifolia has appeared in a few locations, sporadic patches
Lessons learnt- Focus of management Understand biological attributes of the invader, which make them invasives (seed production, vegetative reproduction etc.); Understand why such species have invaded Coordinated management captured by one NSW DPI Regional WMP for both species; Plan for the entire catchment (watershed) and region Eradication vs containment? Relatively easy to treat (if there is Commitment) Integrated Weed Management (Early detection, prevention of spread, herbicides, mechanical removal, burning, cultural control) no bio-control agent yet; not an option in early 1990s because of limited resources and need for more urgent action
Lessons learnt- Focus on management Eradication strategy is workable, so long has the invader has not spread too much Improved reporting and sharing of information Improved Contract specs & contract management; Training (weed contractors) Improved project implementation can bring about successo Eradication should be a goal with these two species o Learning from successful projects o Set performance targets (i.e. reduce local infestations by 50% in i next 12 months.) o Monitor costs, achievement, report
Conclusions Some invasive species are moving with human disturbances These species are only doing what they are meant to do- i.e. exploit vacant niches created by disturbances, maintain fecundity (r- strategists) Spread caused by and sustained by urbanisation impacts Aggressive maintenance control until comprehensive WMPs for areas, regions are produced Stronger insistence on inter-agency cooperation & information sharing Keep a watch on other Ludwigias (L.( hyssopifolia,, L. decurrens,, L. octovalvis) Immigrants to Invaders!! Thank you