2.2.1 Legacy Impacts

Legacy human-use impacts encompass activities that caused significant environmental change in the past and continue to have major effects today, such as historical land clearing, coastal development and overfishing.35 Legacy infrastructure that has modified the movement of water and species between the Reef and its Catchment continues to affect species and habitats 36 (Sections 3.4.10, 3.5, and 6.4.2). Historical commercial exploitation can also have ongoing effects on populations. Some species that were commercially exploited in the past have recovered well, such as humpback whales.35 Populations and habitats can take decades or longer to fully recover to their pre‑disturbance state, and some have been irrevocably altered.37 Species and habitats that have yet to recover from historical disturbances include dugongs, some marine turtles, and certain islands that were cleared and mined for guano. For example, after 100 years of European settlement, many Reef islands still require active pest management programs to treat the legacy of pests introduced more than a century ago,38 although contemporary impacts of recent pest re-incursions can confound the effects of historical introduction.

Legacy human-use impacts continue to have major effects today

Certain legacy impacts to inshore reefs and other habitats are linked to eroded topsoil and sediment particles originating from Catchment areas that have been transported and deposited in the Reef lagoon since European settlement 39 (Section 6.5). During this time, suspended sediments entering the lagoon are estimated to have increased up to five-fold, largely due to human influences.40 These sediments carry a historical record of human activities and land use changes within the Catchment.41 They also represent a large reservoir of nutrients, organic matter, fine particles, and other pollutants, such as pesticides that continue to affect inshore ecosystems 42 (Sections 3.3.1 and 6.5.2). 

Climate change is now part of a suite of legacy impacts, shaping ecosystem compositions and resultant biodiversity, ecosystem functions and services. Warming oceans are leading to novel ecosystem compositions as different species thrive or fail and species range shifts occur.43 In some of these situations returning ecosystems to historical baselines may no longer be possible.

  • 35. Bejder, M., Johnson, D.W., Smith, J., Friedlaender, A. and Bejder, L. 2016, Embracing conservation success of recovering humpback whale populations: evaluating the case for downlisting their conservation status in Australia, Marine Policy 66: 137-141.
  • 36. Queensland Museum 2022, Wetlands of Queensland: Queensland Museum discovery guide/published in partnership with the Department of Environment and Science, South Brisbane.
  • 37. Duarte, C.M., Agusti, S., Barbier, E., Britten, G.L., Castilla, J.C., et al. 2020, Rebuilding marine life, Nature 580(7801): 39-51.
  • 38. Great Barrier Reef Marine Park Authority and Queensland Government 2022, Reef Joint Field Management Program: Annual report summary 2021-2022, Great Barrier Reef Marine Park Authority, Townsville.
  • 39. Collier, C., Brown, A., Fabricius, K., Lewis, S., Diaz-Pulido, G. et al. 2024, 2022 Scientific Consensus Statement: Summary | Evidence Statement for Question 3.2: What are the measured impacts of increased sediment and particulate nutrient loads on GBR ecosystems, what are the mechanism(s) for those impacts and where is there evidence of this occurring in the GBR? in 2022 Scientific Consensus Statement on land-based impacts on Great Barrier Reef water quality and ecosystem condition, eds J. Waterhouse, M. Pineda and K. Sambrook, Commonwealth of Australia and Queensland Government.
  • 40. McCloskey, G.L., Baheerathan, R., Dougall, C., Ellis, R., Bennett, F.R., et al. 2021, Modelled estimates of fine sediment and particulate nutrients delivered from the Great Barrier Reef catchments, Marine Pollution Bulletin 165: 112163.
  • 41. McCulloch, M., Fallon, S., Wyndham, T., Hendy, E., Lough, J., et al. 2003, Coral record of increased sediment flux to the inner Great Barrier Reef since European settlement, Nature 421(6924): 727-730.
  • 42. Waterhouse, J., Pineda, M., Sambrook, K., Newlands, M., McKenzie, L., et al. 2024, 2022 Scientific Consensus Statement: Conclusions, in 2022 Scientific Consensus Statement on land-based impacts on Great Barrier Reef water quality and ecosystem condition, eds J. Waterhouse, M. Pineda and K. Sambrook, Commonwealth of Australia and Queensland Government.
  • 43. Hughes, T.P., Barnes, M.L., Bellwood, D.R., Cinner, J.E., Cumming, G.S., et al. 2017, Coral reefs in the Anthropocene, Nature 546(7656): 82-90.