Kakadu National Park Landscape Symposia Series 2007–2009

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7.4 Conclusions

When combined with field data, modelling approaches such as the one described here allow an understanding of the net effect across the landscape of alternate dispersal curves which reflect plant and/or frugivore attributes. For example, for a species occurring in a different habitat, a different suite of dispersers could be considered and dispersal curves could be altered to reflect the frugivore community, if that information is at hand.

The approach described here requires a detailed understanding of dispersal of native species which may seem like a daunting task. However, the fact that this can be achieved for tropical rainforest habitats which are perhaps the most complex ecosystems in terms of plant-disperser interactions suggests that it could be readily achieved for other systems as well.

Finally, the process described here focuses on animal dispersed weeds, but the concept is equally applicable to predicting and modelling the spread of species that are dispersed by other vectors, eg wind or water. Naturally, the methods utilised to describe dispersal kernels will differ in some respects. As is the case for vertebrate dispersed weeds, the method introduces an explicit consideration of how weeds move through a landscape, forcing consideration of the processes that drive weed spread and consequently encouraging a more strategic approach to management.

References

Buckley YM, Anderson S, Catterall CP, Corlett RT, Engel T, Gosper CR, Nathan R, Richardson DM, Setter M, Spiegel O, Vivian-Smith G, Voight FA, Weir J & Westcott DA 2006. Management of plant invasions mediated by frugivore interactions. Journal of Applied Ecology 43, 848–857.

Csurhes SM 1998. Miconia calvescens, a potentially invasive plant in Australia’s tropical and sub-tropical rainforests. In Proceedings of the First Regional Conference on M. calvescens Control. eds Meyer JY & Smith CW. Papeete, Tahiti, French Polynesia. Gouvernement de Polynésie Française/University of Hawai’i at Manoa/Centre ORSTOM de Tahiti, 72–77.

Dennis AJ & Westcott DA 2007. Estimating dispersal kernels produced by a diverse community of vertebrates. In Seed dispersal: theory and its application in a changing world. eds Dennis AJ, Schupp EW, Green RJ & Westcott DA, CAB International, Wallingford, UK, 201–228.

Kot M, Lewis MA & van den Driessche P 1996. Dispersal data and the spread of invading organisms. Ecology 77, 2027–2042.

Levin SA, Muller-Landau HC, Nathan R & Chave J 2003. The ecology and evolution of seed dispersal: a theoretical perspective. Annual Review of Ecology, Evolution & Systematics 34, 575–604.

Lockwood JL, Cassey P & Blackburn T 2005. The role of propagule pressure in explaining species invasions. Trends in Ecology and Evolution 20, 223–228.

Metcalfe D, Murphy HT, Westcott DA., Sydes T & Vivian-Smith G 2006. Refining Melastome dispersal models in rainforest landscapes. In Proceedings of the 15^th Australian Weeds Conference. eds Preston C, Watts JH & Crossman ND. Weed Management Society of South Australia, Adelaide, 72.

Meyer J-Y 1998a. Observations on the reproductive biology of Miconia calvescens DC (Melastomataceae), an alien invasive tree on the island of Tahiti (South Pacific Ocean). Biotropica 30, 609–624.

Murphy HT, Hardesty BD, Fletcher CS, Metcalfe DJ, Westcott DA & Brooks SJ2008. Predicting dispersal and recruitment of Miconia calvescens (Melastomataceae) in Australian tropical rainforests. Biological Invasions 10, 925–936.

Trakhtenbrot A, Nathan R, Perry G & Richardson DM 2005. The importance of long-distance dispersal in biodiversity conservation. Diversity and Distributions 11, 173–181.

Wang BC, Smith TB 2002. Closing the seed dispersal loop. Trends in ecology and evolution 17, 379–386.

Westcott DA & Dennis AJ 2006. Incorporating dispersal ecology into the management of plant invasions. In Proceedings of the 15^th Australian Weeds Conference. eds Preston C, Watts JH & Crossman ND. Weed Management Society of South Australia, Adelaide, 80–82.

Westcott DA, Bentrupperbäumer J, Bradford MG & McKeown A 2005. Incorporating patterns of disperser behaviour into models of seed dispersal and its effects on estimated dispersal curves. Oecologia 146, 57–67.

8 The weedy time bomb project

G Kyle^¹⁶, M Gardener^¹⁷ & M Ibbett^¹⁸

8.1 Focus summary

Jabiru is a small town located in the centre of Kakadu Natioal Park in Western Arnhem Land. This area is recognised as a biodiversity hotspot. Invasion by exotic weeds poses a major threat to the biodiversity assets of this area.

There are currently 55 introduced species in Jabiru including known invasives like Salvinia, Rubber Vine, Lantana and Ivy Gourd. Many of these species have the capacity to escape into the surrounding landscape.
Major stakeholders in the town of Jabiru have collaborated to design a project and obtain Envirofund support to tackle the weed problem in Jabiru.
The Weedy Time Bomb Project aims to completely eradicate 10 of these species with distributions limited to houses in Jabiru, before they escape to the surrounding landscape.

The project partners identified seven distinct stages of the project. These are:

Community consultation
Mapping of introduced species
Prioritisation of target species
Target species control
Monitoring and evaluation
Education
Supply of alternate garden plants

At the completion of the Envirofund component of the project, partners have committed to 3 years of ongoing monitoring and control to ensure the goal of complete eradication is achieved.