Regional Environmental Change

, Volume 11, Issue 1, pp 19–27 | Cite as

Late 20th century mangrove encroachment in the coastal Australian monsoon tropics parallels the regional increase in woody biomass

  • Grant James Williamson
  • Guy S. Boggs
  • David M. J. S. Bowman
Original Article


In Kakadu National Park, a World Heritage property in the Australian monsoon tropics 250 km to the east of Darwin, a number of recent studies have shown that woody encroachment (expansion of woody communities) and densification (increased biomass in woody communities) has occurred in the last 40 years. The cause of this increase in woody biomass is poorly understood, but possibly associated with the control of invasive Asian water buffalo, trend to higher rainfall, and increased frequency of fires. Mangroves provide an important context to understand these landscape changes, given that they are unaffected by fire or feral water buffalo. We examine change in mangrove distribution in a series of coastal tropical swamps fringing Darwin, Northern Territory, Australia over a 30-year period using a series of 7 aerial photographs spanning 23 years from 1974 and a 2004 high-resolution satellite image. In late 1974, Darwin was impacted by an intense tropical cyclone. Vegetation at 3,000 randomly placed points was manually classified, and a multinomial logistic model was used to asses the impact of landscape position (coastal, intertidal, and upper-tidal) and swamp on mangrove change between 1974 and 2004. Over the study period, there was instability and slight mangrove loss at the coast, stability in the intertidal zone, and mangrove gain in the upper-tidal zone, with an overall increase in mangrove presence of 16.2% above the pre-cyclone distribution. A swamp that was impacted by drainage works for mosquito control and the construction of a sewage treatment plant showed a greater mangrove increase than the two unmodified swamps. The mangrove expansion is consistent with woody encroachment observed in nearby but ecologically distinct systems. Plausible causes for this change include changed local hydrology, changes in sea level, and elevated atmospheric CO2 concentrations.


Mangroves Aerial photography Climate change Coastal ecology Landscape change Vegetation dynamics Woody vegetation 



Funding for this project was provided by the Australian Research Council (ARC) Linkage Grant (No. LP0667619), Northern Territory Department of Health and Community Services, Australian Bureau of Meteorology, Northern Territory Research and Innovation Fund, Australian Department of Defence, and Charles Darwin University. The authors would like to thank the Medical Entomology Branch of the Northern Territory Health Department, especially Peter Whelan for expertise and assistance, the Northern Territory Department of Planning and Infrastructure for assistance with spatial data and equipment, and Lubomir Bisevac and Dimity Boggs for assistance in the field.


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Copyright information

© Springer-Verlag 2010

Authors and Affiliations

  • Grant James Williamson
    • 1
  • Guy S. Boggs
    • 2
  • David M. J. S. Bowman
    • 1
  1. 1.School of Plant ScienceUniversity of TasmaniaHobartAustralia
  2. 2.Tropical Spatial Sciences GroupCharles Darwin UniversityDarwinAustralia

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