Threats: Natural

Cyclones

Cyclones are a relatively frequent occurrence in Far North Queenland and the local ecosystem was shaped by these events in the past. However, the impact of other threats, such as fragmentation and loss of connectivity, and the introduction of pest animals and weeds, have lowered the ecosystem’s resilience, inhibiting recovery from cyclone impacts. Unfortunately, climate change predictions suggest there will be an increase in the intensity of cyclones in the region.

In recent years, Severe Tropical Cyclone Larry (March 2006), and Severe Tropical Cyclone Yasi (February 2011) damaged large areas of cassowary habitat, causing temporary food shortages. This placed further stress on local populations already under threat from habitat fragmentation, dogs and road impacts.

Cyclone Larry, March 2006 (left) and Cyclone Yasi, February 2011 (right)

The Queensland Parks and Wildlife Service (QPWS) helped to reduce this stress by establishing temporary post-cyclone feeding stations. Cassowaries are more likely to survive the lean times by having access to a supplementary food source (mainly fruit kindly donated by local supermarkets) until the forest recovers enough to produce sufficient fruit. Strict protocols around the placement of the stations and restocking draw cassowaries away from roads and urban areas and discourage contact between birds and people to prevent habituation.Unfortunately, at least 18% of all adult and sub-adult cassowaries in the Mission Beach area died in the 12 months after Cyclone Larry hit in March 2006; all the dependent chicks disappeared and were presumed killed in the cyclone (Moore 2008). The full impact of Cyclone Yasi is not yet known.

Climate Change

Models suggest that while the overall frequency of cyclones is unlikely to increase, the warmer sea temperatures may lead to stronger cyclones being experienced more often. This increases the risk of severe ecosystem disruption on a more regular basis.

The storm surge associated with Cyclone Yasi took a heavy toll on littoral rainforest (prime cassowary habitat) between Cardwell and Mission Beach, altering the coastline is some areas so significantly that it will need to be remapped. Future storm surges and rising sea-levels may encroach further into cassowary habitat. Saltwater intrusion into freshwater swamps may negatively impact food plants and drinking sources.

It is difficult to predict what other effects climate change might have on cassowaries, but warmer temperatures and changes in rainfall patterns, might (for example) lead to an increase in the threat of bushfires or disease or to changes in the abundance and variety of food sources and habitat.

Disease

Avian tuberculosis has been diagnosed in wild cassowaries during post mortems. It is believed to be naturally present in the soil but the actions of pigs disturbing soil or contaminating water sources may increase the risk of transmission to cassowaries. Foraging on contaminated food from rubbish dumps may also cause cassowaries to contract tuberculosis or fungal diseases, which can spread rapidly through the population. Aspergillosis is also believed to be a secondary disease in cassowaries causing respiratory symptoms and ultimately mortality. Parasitism of the gut of cassowaries by large numbers of tapeworms has also been recorded.

Not much is known about the prevalence of these diseases in the wild, or how climate change might affect their patterns and incidence, but fortunately, disease does not seem to be a major conservation concern at this time.

Fire

Fire rarely encroaches into the rainforest, but in drier areas bushfires may threaten cassowary habitat. Fire is not usually a significant threat to cassowaries, however after cyclones there may be a high fuel load which can increase the risk in affected areas. Fragmentation of the landscape may leave cassowaries without suitable unburned habitat to move into. People living on rural properties in cassowary habitat should contact the Rural Fire Service Queensland for advice about rural property fire management and safe burning practices.

PHOTO CREDITS: WTMA, QUEENSLAND GOVERNMENT, BUREAU OF METEOROLOGY & NAVAL RESEARCH LAB