Landscape Ecology

, Volume 25, Issue 8, pp 1247–1260 | Cite as

Has global environmental change caused monsoon rainforests to expand in the Australian monsoon tropics?

  • David M. J. S. BowmanEmail author
  • Brett P. Murphy
  • Daniel S. Banfai
Research Article


A large research program in the Australian monsoon tropics has concluded that monsoon rainforests have expanded within the savanna matrix, a trend that has been emulated throughout the tropics worldwide. The driver of the northern Australian trend was not resolved, but it was suggested to be linked to a long-term trend towards wetter climates, atmospheric CO2 enrichment, and changed fire regimes. We review these findings with particular consideration of its analytical and evidentiary basis and plausibility of the global change hypothesis. Field validation has largely demonstrated that the aerial photographic technique that underpinned the previous research is reliable enough to detect rainforest expansion. Statistical modelling demonstrated that the expansion is related to sites with regionally low fire activity, although models are of low explanatory power reflecting the sketchy historical records of fire and feral animal impacts. Field studies show that current fire regimes adjacent to expanding rainforest patches are causing populations of the native conifer Callitris intratropica, an obligate seeder, to crash. Therefore, it is unlikely that changes in fire regimes, which have been deleterious to other fire-sensitive taxa and plant communities in the region, are responsible for the rainforest expansion. We conclude that the expansion of monsoon rainforests is most plausibly linked to the current wetting trend or elevated CO2 concentration. Increases in either water availability or CO2 concentration can potentially overwhelm the negative feedback between fire and rainforest cover that is responsible for the meta-stability of monsoon rainforest boundaries. However, further research at the continental scale, using aerial photography, tree rings and other proxies, is required to evaluate this hypothesis.


Aerial photography Allosyncarpia ternata Climate change Closed forest CO2 Eucalypt Fire Monsoon rainforest Rainfall Tropical savanna 



This work was supported by the Australian Research Council (Grants LP0346929 and DP0878177) and Kakadu National Park.


  1. Ainsworth EA, Long SP (2005) What have we learned from 15 years of free-air CO2 enrichment (FACE)? A meta-analytic review of the responses of photosynthesis, canopy properties and plant production to rising CO2? New Phytol 165:351–372CrossRefPubMedGoogle Scholar
  2. Allan GE, Southgate RI (2002) Fire regimes in the spinifex landscapes of Australia. In: Bradstock RA, Williams JE, Gill MA (eds) Flammable Australia: the fire regimes and biodiversity of a continent. Cambridge University Press, Cambridge, pp 145–176Google Scholar
  3. Archer S, Schimel DS, Holland EA (1995) Mechanisms of shrubland expansion: landuse, climate or CO2? Clim Change 29:91–99CrossRefGoogle Scholar
  4. Archer S, Boutton TW, Hibbard KA (2000) Trees in grasslands: biogeochemical consequences of woody plant expansion. In: Schulze E-D, Harrison SP, Heimann M, Holland EA, Lloyd J, Prentice IC, Schimel D (eds) Global biogeochemical cycles in the climate system. Academic Press, San Diego, pp 115–137Google Scholar
  5. Ash J (1983) Tree rings in tropical Callitris macleayana F. Muell. Aust J Bot 31:277–281CrossRefGoogle Scholar
  6. Baker PJ, Palmer JG, D’Arrigo R (2008) The dendrochronology of Callitris intratropica in northern Australia: annual ring structure, chronology development and climate correlations. Aust J Bot 56:311–320CrossRefGoogle Scholar
  7. Banfai DS, Bowman DMJS (2005) Dynamics of a savanna-forest mosaic in the Australian monsoon tropics inferred from stand structures and historical aerial photography. Aust J Bot 53:185–194CrossRefGoogle Scholar
  8. Banfai DS, Bowman DMJS (2006) Forty years of lowland monsoon rainforest expansion in Kakadu National Park, northern Australia. Biol Conserv 131:553–565CrossRefGoogle Scholar
  9. Banfai DS, Bowman DMJS (2007) Drivers of rain-forest boundary dynamics in Kakadu National Park, northern Australia: a field assessment. J Trop Ecol 23:73–86CrossRefGoogle Scholar
  10. Berry SL, Roderick ML (2002) CO2, and land-use effects on Australian vegetation over the last two centuries. Aust J Bot 50:511–531CrossRefGoogle Scholar
  11. Berryman CA, Eamus D, Duff GA (1993) The influence of CO2 enrichment on growth, nutrient content and biomass allocation of Maranthes corymbosa. Aust J Bot 41:195–209CrossRefGoogle Scholar
  12. Bond WJ, Midgley GF (2000) A proposed CO2-controlled mechanism of woody plant invasion in grasslands and savannas. Glob Chang Biol 6:865–869CrossRefGoogle Scholar
  13. Bowman DMJS (1991) Recovery of some northern Australian monsoon forest tree species following fire. Proc R Soc Qld 101:21–25Google Scholar
  14. Bowman DMJS (2000a) Australian rainforests: islands of green in the land of fire. Cambridge University Press, CambridgeCrossRefGoogle Scholar
  15. Bowman DMJS (2000b) Rainforests and flame forests: the great Australian forest dichotomy. Aust Geogr Stud 38:340–344CrossRefGoogle Scholar
  16. Bowman DMJS (2001) On the elusive definition of ‘Australian rainforest’: response to Lynch and Neldner (2000). Aust J Bot 49:785–787CrossRefGoogle Scholar
  17. Bowman DMJS (2005) Understanding a flammable planet—climate, fire and global vegetation patterns. New Phytol 165:341–345CrossRefPubMedGoogle Scholar
  18. Bowman DMJS, Dingle JK (2006) Late 20th century landscape-wide expansion of Allosyncarpia ternata (Myrtaceae) forests in Kakadu National Park, northern Australia. Aust J Bot 54:707–715CrossRefGoogle Scholar
  19. Bowman DMJS, Harris S (1995) Conifers of Australia’s dry forests and open woodlands. In: Enright NJ, Hill RS (eds) Ecology of the southern conifers. Melbourne University Press, Melbourne, pp 252–270Google Scholar
  20. Bowman DMJS, Panton WJ (1993) Decline of Callitris intratropica Baker, R.T. and Smith, H.G. in the Northern Territory—implications for pre-European and post-European colonization fire regimes. J Biogeogr 20:373–381CrossRefGoogle Scholar
  21. Bowman DMJS, Wilson BA (1988) Fuel characteristics of coastal monsoon forests, Northern Territory, Australia. J Biogeogr 15:807–817CrossRefGoogle Scholar
  22. Bowman DMJS, Woinarski JCZ (1994) Biogeography of Australian rainforest mammals: implications for the conservation of rainforest mammals. Pac Conserv Biol 1:98–106Google Scholar
  23. Bowman DMJS, Wilson BA, McDonough L (1991) Monsoon forests in northwestern Australia. 1. Vegetation classification and the environmental control of tree species. J Biogeogr 18:679–686CrossRefGoogle Scholar
  24. Bowman DMJS, Woinarski JCZ, Russell-Smith J (1994) Environmental relationships of orange-footed scrubfowl Megapodius reinwardt nests in the Northern Territory. Emu 94:181–185CrossRefGoogle Scholar
  25. Bowman DMJS, Price O, Whitehead PJ, Walsh A (2001a) The ‘wilderness effect’ and the decline of Callitris intratropica on the Arnhem Land Plateau, northern Australia. Aust J Bot 49:665–672CrossRefGoogle Scholar
  26. Bowman DMJS, Walsh A, Milne DJ (2001b) Forest expansion and grassland contraction within a Eucalyptus savanna matrix between 1941 and 1994 at Litchfield National Park in the Australian monsoon tropics. Glob Ecol Biogeogr 10:535–548CrossRefGoogle Scholar
  27. Bowman DMJS, Cook GD, Zoppi U (2004a) Holocene boundary dynamics of a northern Australian monsoon rainforest patch inferred from isotopic analysis of carbon, (14C and δ13C) and nitrogen (δ15N) in soil organic matter. Austral Ecol 29:605–612CrossRefGoogle Scholar
  28. Bowman DMJS, Walsh A, Prior LD (2004b) Landscape analysis of Aboriginal fire management in Central Arnhem Land, north Australia. J Biogeogr 31:207–223CrossRefGoogle Scholar
  29. Bowman DMJS, Boggs GS, Prior LD, Krull ES (2007) Dynamics of Acacia aneura-Triodia boundaries using carbon (14C and δ13C) and nitrogen (δ15N) signatures in soil organic matter in central Australia. Holocene 17:311–318CrossRefGoogle Scholar
  30. Bowman DMJS, Boggs GS, Prior LD (2008a) Fire maintains an Acacia aneura shrubland-Triodia grassland mosaic in central Australia. J Arid Environ 72:34–47CrossRefGoogle Scholar
  31. Bowman DMJS, Riley JE, Boggs GS, Lehmann CER, Prior LD (2008b) Do feral buffalo (Bubalus bubalis) explain the increase of woody cover in savannas of Kakadu National Park, Australia? J Biogeogr 35:1976–1988CrossRefGoogle Scholar
  32. Bowman DMJS, Brown GK, Braby MF, Brown JR, Cook LG, Crisp MD, Ford F, Haberle S, Hughes J, Isagi Y, Joseph L, McBride J, Nelson G, Ladiges PY (2009) Biogeography of the Australian monsoon tropics. J Biogeogr 37:201–216CrossRefGoogle Scholar
  33. Bradshaw CJA, Sodhi NS, Peh KS-H, Brook BW (2007) Global evidence that deforestation amplifies flood risk and severity in the developing world. Glob Chang Biol 13:2379–2395CrossRefGoogle Scholar
  34. Bradshaw CJA, Sodhi NS, Brook BW (2008) Tropical turmoil: a biodiversity tragedy in progress. Front Ecol Environ 7:79–87CrossRefGoogle Scholar
  35. Brook BW, Bowman DMJS (2006) Postcards from the past: charting the landscape-scale conversion of tropical Australian savanna to closed forest during the 20th century. Landscape Ecol 21:1253–1266CrossRefGoogle Scholar
  36. Bureau of Meteorology (2009) Climate data online,
  37. Cochrane MA (2001) Synergistic interactions between habitat fragmentation and fire in evergreen tropical forests. Conserv Biol 15:1515–1521CrossRefGoogle Scholar
  38. Cochrane MA (2003) Fire science for rainforests. Nature 421:913–919CrossRefPubMedGoogle Scholar
  39. Cullen LE, Grierson PF (2009) Multi-decadal scale variability in autumn-winter rainfall in south-western Australia since 1655 AD as reconstructed from tree rings of Callitris columellaris. Clim Dyn 33:433–444CrossRefGoogle Scholar
  40. D’Antonio CM, Vitousek PM (1992) Biological invasions by exotic grasses, the grass/fire cycle, and global change. Annu Rev Ecol Syst 23:63–87Google Scholar
  41. Fensham RJ, Fairfax RJ, Butler DW, Bowman DMJS (2003a) Effects of fire and drought in a tropical eucalypt savanna colonized by rain forest. J Biogeogr 30:1405–1414CrossRefGoogle Scholar
  42. Fensham RJ, Low Choy SJ, Fairfax RJ, Cavallaro PC (2003b) Modelling trends in woody vegetation structure in semi-arid Australia as determined from aerial photography. J Environ Manag 68:421–436CrossRefGoogle Scholar
  43. Field RD, van der Werf GR, Shen SSP (2009) Human amplification of drought-induced biomass burning in Indonesia since 1960. Nat Geosci 2:185–188CrossRefGoogle Scholar
  44. Franklin DC (1999) Evidence of disarray amongst granivorous bird assemblages in the savannas of northern Australia, a region of sparse human settlement. Biol Conserv 90:53–68CrossRefGoogle Scholar
  45. Griffin GF, Price NF, Portlock HF (1983) Wildfires in the central Australian rangelands, 1970–1980. J Environ Manag 17:311–323Google Scholar
  46. Guillet B, Achoundong G, Happi JY, Beyala VKK, Bonvallot J, Riera B, Mariotti A, Schwartz D (2001) Agreement between floristic and soil organic carbon isotope (13C/12C, 14C) indicators of forest invasion of savannas during the last century in Cameroon. J Trop Ecol 17:809–832CrossRefGoogle Scholar
  47. Harrington GN, Sanderson KD (1994) Recent contraction of wet sclerophyll forest in the wet tropics of Queensland due to invasion by rainforest. Pac Conserv Biol 1:319–327Google Scholar
  48. Hennessy KJ, Suppiah R, Page CM (1999) Australian rainfall changes, 1910–1995. Aust Meteorol Mag 48:1–13Google Scholar
  49. Hennessy K, Fitzharris B, Bates BC, Harvey N, Howden SM, Hughes L, Salinger J, Warrick R (2007) Australia and New Zealand. In: Parry ML, Canziani OF, Palutikof JP, van der Linden PJ, Hanson CE (eds) Climate change 2007: impacts, adaptation and vulnerability. Contribution of working group II to the fourth assessment report of the intergovernmental panel on climate change. Cambridge University Press, Cambridge, pp 507–540Google Scholar
  50. Keeling CD, Whorf TP (2004) Atmospheric CO2 records from sites in the SIO air sampling network. Trends: a compendium of data on global change. Carbon Dioxide Information Analysis Center, U.S. Department of Energy, Oak Ridge, TN, USAGoogle Scholar
  51. Latz P (1995) Bushfires and bushtucker: aboriginal plant use in Central Australia. IAD Press, Alice SpringsGoogle Scholar
  52. Laurance WF, Williamson GB (2001) Positive feedbacks among forest fragmentation, drought, and climate change in the Amazon. Conserv Biol 15:1529–1535CrossRefGoogle Scholar
  53. Lehmann CER, Prior LD, Bowman DMJS (2009) Decadal dynamics of tree cover in an Australian tropical savanna. Austral Ecol 34:601–612CrossRefGoogle Scholar
  54. Lewis SL, Malhi Y, Phillips OL (2004) Fingerprinting the impacts of global change on tropical forests. Philos Trans R Soc Lond B Biol Sci 359:437–462CrossRefPubMedGoogle Scholar
  55. Lewis SL, Lopez-Gonzalez G, Sonké B, Affum-Baffoe K, Baker TR, Ojo LO, Phillips OL, Reitsma JM, White L, Comiskey JA, M-N DjuikouoK, Ewango CEN, Feldpausch TR, Hamilton AC, Gloor M, Hart T, Hladik A, Lloyd J, Lovett JC, Makana J-R, Malhi Y, Mbago FM, Ndangalasi HJ, Peacock J, Peh KS-H, Sheil D, Sunderland T, Swaine MD, Taplin J, Taylor D, Thomas SC, Votere R, Wöll H (2009) Increasing carbon storage in intact African tropical forests. Nature 457:1003–1006CrossRefPubMedGoogle Scholar
  56. Loarie SR, Asner GP, Field CB (2009) Boosted carbon emissions from Amazon deforestation. Geophys Res Lett 36:L14810CrossRefGoogle Scholar
  57. Lunt I, Winsemius L, McDonald S, Morgan J, Dehaan R (2010) How widespread is woody plant encroachment in temperate Australia? Changes in woody vegetation cover in lowland woodland and coastal ecosystems in Victoria from 1989 to 2005. J Biogeogr 37:722–732CrossRefGoogle Scholar
  58. Mitchard ETA, Saatchi SS, Gerard FF, Lewis SL, Meir P (2009) Measuring woody encroachment along a forest-savanna boundary in central Africa. Earth Interact 13:8CrossRefGoogle Scholar
  59. Murphy BP, Russell-Smith J, Prior LD (2010a) Frequent fires reduce tree growth rates in northern Australian savannas: implications for tree demography and carbon sequestration. Glob Chang Biol 16:331–343CrossRefGoogle Scholar
  60. Murphy BP, Paron P, Prior LD, Boggs GS, Franklin DC, Bowman DMJS (2010b) Using generalized autoregressive error models to understand fire-vegetation-soil feedbacks in a mulga-spinifex landscape mosaic. J BiogeogrGoogle Scholar
  61. Nicholas AMM, Franklin DC, Bowman DMJS (2009) Co-existence of shrubs and grass in a semi-arid landscape: a case study of mulga (Acacia aneura, Mimosaceae) shrublands embedded in fire-prone spinifex (Triodia pungens, Poaceae) hummock grasslands. Aust J Bot 57:396–405CrossRefGoogle Scholar
  62. Phillips OL (1995) Evaluating turnover in tropical forests. Response to Sheil. Science 268:894–895CrossRefPubMedGoogle Scholar
  63. Phillips OL, Gentry AH (1994) Increasing turnover through time in tropical forests. Science 263:954–958CrossRefPubMedGoogle Scholar
  64. Price OF, Woinarski JCZ, Robinson D (1999) Very large area requirements for frugivorous birds in monsoon rainforests of the Northern Territory, Australia. Biol Conserv 91:169–180CrossRefGoogle Scholar
  65. Prior LD, Eamus D, Bowman DMJS (2003) Leaf attributes in the seasonally dry tropics: a comparison of four habitats in northern Australia. Funct Ecol 17:504–515CrossRefGoogle Scholar
  66. Prior LD, Bowman DMJS, Eamus D (2004a) Seasonal differences in leaf attributes in Australian tropical tree species: family and habitat comparisons. Funct Ecol 18:707–718CrossRefGoogle Scholar
  67. Prior LD, Eamus D, Bowman DMJS (2004b) Tree growth rates in north Australia savanna habitats: seasonal patterns and correlations with leaf attributes. Aust J Bot 52:303–314CrossRefGoogle Scholar
  68. Prior LD, Bowman DMJS, Brook BW (2007) Growth and survival of two north Australia relictual tree species, Allosyncarpia ternata (Myrtaceae) and Callitris intratropica (Cupressaceae). Ecol Res 22:228–236CrossRefGoogle Scholar
  69. Prior LD, Murphy BP, Russell-Smith J (2009) Environmental and demographic correlates of tree recruitment and mortality in north Australian savannas. For Ecol Manag 257:66–74CrossRefGoogle Scholar
  70. Puyravaud J-P, Dufour C, Aravajy S (2003) Rainforest expansion mediated by successional processes in vegetation thickets in the Western Ghats of India. J Biogeogr 30:1067–1080CrossRefGoogle Scholar
  71. Roques KG, O’Connor TG, Watkinson AR (2001) Dynamics of shrub encroachment in an African savanna: relative influences of fire, herbivory, rainfall and density dependence. J Appl Ecol 38:268–280CrossRefGoogle Scholar
  72. Russell-Smith J (1991) Classification, species richness, and environmental relations of monsoon rain forest in northern Australia. J Veg Sci 2:259–278CrossRefGoogle Scholar
  73. Russell-Smith J, Bowman DMJS (1992) Conservation of monsoon rainforest isolates in the Northern Territory, Australia. Biol Conserv 59:51–63CrossRefGoogle Scholar
  74. Russell-Smith J, Lucas DE, Brock J, Bowman DMJS (1993) Allosyncarpia-dominated rain forest in monsoonal northern Australia. J Veg Sci 4:67–82CrossRefGoogle Scholar
  75. Russell-Smith J, Ryan PG, Durieu R (1997) A LANDSAT MSS-derived fire history of Kakadu National Park, monsoonal northern Australia, 1980–94: seasonal extent, frequency and patchiness. J Appl Ecol 34:748–766CrossRefGoogle Scholar
  76. Russell-Smith J, Ryan PG, Cheal DC (2002) Fire regimes and the conservation of sandstone heath in monsoonal northern Australia: frequency, interval, patchiness. Biol Conserv 104:91–106CrossRefGoogle Scholar
  77. Russell-Smith J, Stanton PJ, Edwards AC, Whitehead PJ (2004a) Rain forest invasion of eucalypt-dominated woodland savanna, Iron Range, north-eastern Australia: II. Rates of landscape change. J Biogeogr 31:1305–1316CrossRefGoogle Scholar
  78. Russell-Smith J, Stanton PJ, Whitehead PJ, Edwards AC (2004b) Rain forest invasion of eucalypt-dominated woodland savanna, Iron Range, north-eastern Australia: I. Successional processes. J Biogeogr 31:1293–1303CrossRefGoogle Scholar
  79. Russell-Smith J, Price OF, Murphy BP (2010) Managing the matrix: decadal responses of eucalypt-dominated mesic savanna to ambient fire regimes in three north Australian conservation reserves. Ecol ApplGoogle Scholar
  80. Schwartz D, de Foresta H, Mariotti A, Balesdent J, Massimba JP, Girardin C (1996) Present dynamics of the savanna-forest boundary in the Congolese Mayombe: a pedological, botanical and isotopic (13C and 14C) study. Oecologia 106:516–524CrossRefGoogle Scholar
  81. Sharp BR, Bowman DMJS (2004) Patterns of long-term woody vegetation change in sandstone-plateau savanna woodland, Northern Territory, Australia. J Trop Ecol 20:259–270CrossRefGoogle Scholar
  82. Sharp BR, Whittaker RJ (2003) The irreversible cattle-driven transformation of a seasonally flooded Australia savanna. J Biogeogr 30:783–802CrossRefGoogle Scholar
  83. Sheil D (1995) Evaluating turnover in tropical forests. Science 268:894CrossRefPubMedGoogle Scholar
  84. Sheil D, Murdiyarso D (2009) How forests attract rain: an examination of a new hypothesis. Bioscience 59:341–347CrossRefGoogle Scholar
  85. Smith I (2004) An assessment of recent trends in Australian rainfall. Aust Meteorol Mag 53:163–173Google Scholar
  86. Wigley BJ, Bond WJ, Hoffmann MT (2009) Thicket expansion in a South African savanna under divergent land use: local vs. global drivers? Glob Chang Biol 16:964–976CrossRefGoogle Scholar
  87. Williams J (2002) Fire regimes and their impacts in the mulga (Acacia aneura) landscapes of central Australia. In: Russell-Smith J, Craig R, Gill AM, Smith R, Williams J (eds) Australian fire regimes: contemporary patterns (April 1998–March 2000) and changes since European settlement. Department of the Environment and Heritage, CanberraGoogle Scholar
  88. Williamson GJ, Boggs GS, Bowman DMJS (2010) Late 20th century mangrove encroachment in the coastal Australian monsoon tropics parallels the regional increase in woody biomass. Reg Environ ChangGoogle Scholar
  89. Woinarski JCZ, Milne DJ, Wanganeen G (2001) Changes in mammal populations in relatively intact landscapes of Kakadu National Park, Northern Territory, Australia. Austral Ecol 26:360–370CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media B.V. 2010

Authors and Affiliations

  • David M. J. S. Bowman
    • 1
    Email author
  • Brett P. Murphy
    • 1
  • Daniel S. Banfai
    • 2
  1. 1.School of Plant ScienceUniversity of TasmaniaHobartAustralia
  2. 2.Earth SystemsKewAustralia

Personalised recommendations