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The Arafura Swamp is a globally significant wooded wetland in central Arnhem Land providing important habitat for migratory birds and fish. It is, however, threatened by saltwater intrusions from rising sea levels and a range of other threats including some cattle grazing, inappropriate fire regimes and feral plant and animal invasions. Three Indigenous Ranger groups are working to address these management issues but need stronger levels of support to be able to secure ongoing and long-term management solutions for this important wetland.
The award-winning film Ten Canoes opens with an aerial shot tracing the sinuous course of the Goyder River through the Arafura Swamp as the narrator tells us the story begins ‘…longtime ago. It is our time, before you other mob come from cross the ocean…longtime before then. The rain’s been good and ten of the men go on the swamp, to hunt the eggs of gumang, the magpie goose’. Yolngu people have been living on, and caring for, Arafura Swamp in central Arnhem Land for millennia. The goose egg hunt continues; except nowadays, its success is influenced by more than the weather, e.g., weeds, feral animals and wildfires lit by unauthorised people during dry periods. These and other threats – like saltwater intrusion and even the long-term impacts of climate change – are being addressed by three Aboriginal ranger groups working cooperatively to protect and manage the international values of the Arafura Swamp and surrounding land and sea country.
The Arafura Swamp
The Arafura Swamp is a large freshwater basin (∼700 km2) located on the northern coast of Arnhem Land, about 460 km from Darwin, Northern Territory (NT), Australia (Fig. 1). It occupies the broad floodplain of the Goyder and Gulbuwangay Rivers and abuts the tidally influenced coastal plain of Castlereagh Bay in the north. It is unique in the Top End (i.e. the northern tropical region of the Northern Territory) because of its extensive perennial swamps (fed by springs along the Goyder River) and lack of a continuous river channel to the sea (Harrison et al. 2009). This means that at least part of the Swamp remains permanently flooded throughout the year. The permanent swamps support a diverse range of extensive, intact wetland habitats that are relatively rare elsewhere in the Top End. Much of the Swamp is covered by open paperbark (Melaleuca spp.) forest and woodland, making it one of the largest wooded swamps in the NT and possibly one of the largest in Australia (Directory of Important Wetlands in Australia (DIWA) 2011).
The Arafura Swamp is Aboriginal freehold land and is part of the Arnhem Land Aboriginal Land Trust. The Swamp and surrounding country mainly supports Indigenous use; Murwangi Station, on the western side, is used for pastoral operations. The area is sparsely populated, but the Aboriginal community of Ramingining (population 650) is located close to the north-western edge of the Swamp (Fig. 1).
The large and diverse wetland habitats of the Arafura Swamp support large numbers of waterbirds (over 300 000) at times. Magpie Geese (Anseranus semipalmata) and egrets (Ardea spp., and Egretta spp.) are most often the dominant species, but at least eight other species, including the Black-necked Stork (Ephippiorhynchus asiaticus), Brolga (Grus rubicundus), Radjah Shelduck (Tadorna radjah) and Royal Spoonbill (Platalea regia), occur in internationally significant numbers (Harrison et al. 2009). The Swamp and adjacent tidal flats of Castlereagh Bay are an internationally recognised Important Bird Area owing to the occurrence of globally significant numbers of a range of waterbird and shorebird species (BirdLife Data Zone 2011).
Seven threatened species are reported from the Arafura Swamp, along with 17 species listed under international conventions or bilateral agreements protecting migratory animals (Harrison et al. 2009; DIWA 2011). The spectacular-looking Threadfin Rainbowfish (Iriatherina werneri), previously known only from Cape York and New Guinea, was recently discovered, and the Swamp is an important refuge and breeding area for both saltwater and freshwater crocodile species (Crocodylus spp.) (Australian Heritage Council 2011a).
Numerous rainforest patches occur around the margin of the Swamp, and the southern part contains the largest area of Hanguana malayana swamp (a restricted freshwater wetland community) in the NT and vast areas of other freshwater wetland species when compared to the rest of the NT (Harrison et al. 2009). The Arafura wetlands also contain almost the entire NT population of the large distinctive wetland palm Corypha utan, more commonly known as Gebang Palm, or Cabbage Palm (Brennan et al. 2003) (Fig. 2).
The Arafura Swamp and Arafura Jungles sites are listed on the Register of the National Estate for their natural values (Australian Heritage Council 2011a,b). The Arafura Swamp is a wetland of national importance (DIWA 2011), and an assessment by Brennan et al. (2003) found that it satisfies most Ramsar criteria for listing as a wetland of international importance. The Swamp was also given an ‘international’ rating in an inventory of sites of international and national significance for biodiversity values in the NT (Harrison et al. 2009).
Threats to the Swamp
According to Harrison et al. (2009), saltwater intrusion is one of the major threats to the ecological and cultural values of the Arafura Swamp. Sea-level rise resulting from climate change could directly affect the freshwater wetlands. Grazing cattle are also damaging fragile banks and waterways in the northern part where freshwater and tidal areas meet. Other key threats are listed as follows.
Fire is a natural part of the local vegetation dynamics, but inappropriate fire regimes are likely to have killed large areas of paperbarks and degraded some local environments. In the period 1993–2004, 25% of the Swamp was burnt in fewer than 3 years, and 7% was burnt in more than 6 years. Small and controlled fires are still used by locals while they are hunting, but the area is vulnerable to extensive wildfires lit by unauthorised people during dry periods.
Although current populations of Water Buffalo (Bubalis bubalis), feral Pig (Sus scrofa) and Cattle (Bos spp.) in the Swamp are not high, they cause considerable physical damage to the wetland environments. Cane Toad (Rhinella marina) and feral Cat (Felis catus) are also present in the Arafura catchment.
Weed establishment is currently quite low, but some serious weeds are present that need to be managed. Two weeds of National Significance (Mimosa, Mimosa pigra; and Olive Hymenachne, Hymenachne amplexicaulis), seven weeds declared under the NT Weed Management Act, and four other undeclared but problematic environmental weeds have been recorded from the Swamp.
Protection and management of the Swamp
Three community-based Aboriginal ranger groups, based at Ramingining, Murwangi station and Mirrnatja, are working collaboratively with NT Government departments and others to protect and manage the Arafura Swamp. The three groups – Gurruwiling, South-East Arafura Catchment and Wanga Djakamirr – are presented in detail in Box 1, but in summary, they are managing and monitoring Mimosa and other priority weeds in the region, actively culling Pig populations and have fenced off significant rainforest patches and sacred sites to exclude feral herbivores. They are patrolling for illegal fishing vessels and doing quarantine work (e.g. survey and monitoring for early detection of exotic pest plants and vertebrates, collecting samples for disease detection), undertaking regular Saltwater Crocodile (Crocodylus porosus) surveys (to determine the location of nest sites and the presence of problem crocodiles as well as to monitor distribution and abundance) and participating in comprehensive biological surveys. The rangers work with research organisations to apply adaptive fire management (North Australian Indigenous Land and Sea Management Alliance (NAILSMA) 2010) and monitor for saltwater intrusion. Together, they are helping implement the recently reviewed Integrated Natural Resource Management Plan (INRM Plan) for the NT by addressing key threats to the internationally significant values of the Arafura Swamp (management action 72 in Territory Natural Resource Management 2011).
It is hoped that the ranger groups will continue to grow and prosper. It is worth noting, however, the observations of Brennan et al. (2003), who wrote that ‘short term and unstable management programmes…are unhelpful to maintaining the conservation values of the Swamp’. In other words, stable funding is crucial to maintaining stable management.
The challenges faced by Gurruwiling, South-East Arafura Catchment and Wanga Djakamirr Rangers are often typical of other Indigenous ranger groups in the NT and are not simply expressed. Short-term funding cycles, shifting government priorities, organisational instability in remote Australia, governance issues and the disparity in values between policy makers and Indigenous Australians are parts of the contemporary narrative, but not the whole story, and in some cases also present opportunities. Perhaps, one is to be found in a low-carbon market economy where customary activities, like controlled savanna burning to reduce wildfires, and hence greenhouse gas emissions, could provide a reliable future source of income (Fitzsimons et al. 2012).
The Gurruwiling Rangers consist of about five Traditional Owners for the Arafura Swamp. They have been operating since 2004. Although the main area of operations is the central and north-west Swamp, these rangers possess expertise that means they are in demand for much of the area around Ramingining and its outstation. The group was originally based at Murwangi Station, on the edge of the Swamp, but are now based at Ramingining (Fig. 3).
The group began formal training in the crocodile harvesting industry in 2004 with eight rangers completing a Certificate 1 in Aquaculture (Live Crocodile Handling). They continue to use their skills in ongoing crocodile survey and egg harvest, under permit, for croc farms in the NT. Other activities include early season burn-offs to prevent late season wildfires and weed management activities focussed on Mimosa and Olive Hymenachne. Most of the rangers participated in the filming of Ten Canoes. Traditional Ecological Knowledge has also been recorded by skilled senior rangers.
South-East Arafura catchment
This is a small group. It has no formal structure but consists of one senior man and a number of other participants who assist in varying degrees in land management. The group is organised along customary lines and has no coordinator and work closely with the Gurruwiling Rangers.
The group operates out of the small community of Mirrnatja and over the southern and south-eastern part of the Arafura Swamp and upstream catchments. It began in the early 1990s with assistance from Monash University in Melbourne. In part, the group’s creation was because of the listing of the Arafura Swamp on the Register of the National Estate. The group was created with the goal of continuing customary land management practices and being an entity through which contemporary land management practices could be addressed, broadly, to look after country. This for the most part consists of ensuring traditional land management, such as burning and ceremony, takes place. However, the group increasingly has to deal with alien threats such as weeds and feral animals. Great efforts are being made to ensure that the area remains free of Mimosa and that Pigs are controlled in those areas that are accessible.
The control of Mimosa has been a key achievement of this group. Although it has been present in this area for more than 15 years, a recent systematic survey found no plants.
The Wanga Djakamirr Rangers comprise Yolngu people from several language groups in and around Ramingining. They focus their activities on the northern part of the Arafura Swamp and catchment including the Glyde River floodplains and estuary. The rangers provide services to eight homeland areas. Fishing patrol activities are focussed on the rivers and channels around Milingimbi and the mainland. These patrols have resulted in less illegal fishing and one illegal fishing prosecution. The group recently commenced a project with Charles Darwin University investigating saltwater intrusion in the Swamp. Other work includes the identification, surveying and control of weeds such as Mission Grass (Pennisetum polystachion), snake weeds (Stachytarpheta spp.) and Para Grass (Brachiaria mutica). Track maintenance is undertaken to reduce erosion and keep tracks free of fallen trees and rainforest patches, and sacred sites are protected from feral animals by erection of exclusion fencing (Fig. 4).
A community-based land management programme, the Wanga Djakamirr Rangers, was established in 1997, and the programme was run out of the Ramingining Homelands Resource Centre until it went into administration in late 2010.
All three ranger groups are currently managed by the Northern Land Council, based on Darwin.
The Arafura Swamp is a wetland of international significance. While still relatively undisturbed and in good condition, degradation is evident in the swamp/estuarine interface. Populations of weeds and feral animals are currently low and manageable, but there is huge potential for extensive degradation of wetland habitat if they are left unchecked. Saltwater intrusion is one of the major threats, while large and frequent fires and inundation from sea-level rise are of increasing concern. While three Aboriginal ranger groups are working hard to deal with all this, they can do little about unstable management programmes and funding opportunities which have the potential to undermine their good work – and goodwill – and become the greatest threat to the ecological and cultural values of the Swamp. It is possible that ranger participation in a future carbon market might be one solution to this heretofore intractable problem.