Humans' construction 'footprint' on ocean quantified
Aquaculture farms in the coast of China鈥檚 northeast province of Liaonin. Credit: NASA Earth Observatory.
In a world-first, the extent of human development in oceans has been mapped. An area totalling approximately 30,000 square kilometres 鈥� the equivalent of 0.008 percent of the ocean 鈥� has been modified by human construction, a study led by Dr Ana Bugnot from the University of Sydney School of Life and Environmental Sciences and the has found.
The extent of ocean modified by human construction is, proportion-wise, comparable to the extent of urbanised land, and greater than the global area of some natural marine habitats, such as mangrove forests and seagrass beds.
When calculated as the area modified inclusive of flow-on effects to surrounding areas, for example, due to changes in water flow and pollution, the footprint is actually two million square kilometres, or over 0.5 percent of the ocean.
The oceanic modification includes areas affected by tunnels and bridges; infrastructure for energy extraction (for example, oil and gas rigs, wind farms); shipping (ports and marinas); aquaculture infrastructure; and artificial reefs.
Dr Bugnot said that ocean development is nothing new, yet, in recent times, it has rapidly changed. 鈥淚t has been ongoing since before 2000 BC,鈥� she said. 鈥淭hen, it supported maritime traffic through the construction of commercial ports and protected low-lying coasts with the creation of structures similar to breakwaters.
鈥淪ince the mid-20th century, however, ocean development has ramped up, and produced both positive and negative results.
鈥淔or example, while artificial reefs have been used as 鈥榮acrificial habitat鈥� to drive tourism and deter fishing, this infrastructure can also impact sensitive natural habitats like seagrasses, mudflats and saltmarshes, consequently affecting water quality.
鈥淢arine development mostly occurs in coastal areas 鈥� the most biodiverse and biologically productive ocean environments.鈥�
Map of physical footprint of marine construction globally, in square kilometres. Credit: Bugnot et al., 鈥楥urrent and projected global extent of marine built structures鈥�, Nature Sustainability.
Future expansion 鈥榓larming鈥�
Dr Bugnot, joined by co-researchers from multiple local and international universities, also projected the rate of future ocean footprint expansion.
鈥淭he numbers are alarming,鈥� Dr Bugnot said. 鈥淔or example, infrastructure for power and aquaculture, including cables and tunnels, is projected to increase by 50 to 70 percent by 2028.
鈥淵et this is an underestimate: there is a dearth of information on ocean development, due to poor regulation of this in many parts of the world.
鈥淭here is an urgent need for improved management of marine environments. We hope our study spurs national and international initiatives, such as the , to greater action.鈥�
The researchers attributed the projected expansion on people鈥檚 increasing need for defences against coastal erosion and inundation due to sea level rise and climate change, as well as their transportation, energy extraction, and recreation needs.
Journal Nature Sustainability published their research. It was undertaken in 2018, when Dr Bugnot was employed by UNSW.
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Funding declaration: This research was supported by the Australian Research Council; the Maple Brown Foundation; the Ian Potter Foundation; the World Harbour Project; the New South Wales Government Office of Science and Research; and the Macquarie University FSE Visiting Researcher Fellowship Scheme.