Man-made constructions are modifying oceans at an alarming rate

In a first, a new study by researchers from the University of Sydney School of Life and Environmental Sciences and the Sydney Institute of Marine Science has quantified and mapped the extent of human development in oceans. Published in the Nature Sustainability journal on 31 August, the study looks at the extent of how human construction—everything from tunnels and bridges to infrastructure for energy extraction—has modified the ocean.

Dr Ana Bugnot, from the University of Sydney School of Life and Environmental Sciences, led this study and said that while ocean development is “nothing new", it has rapidly changed in recent times. “It has been ongoing since before 2000 BC," she said in an official release. “Then, it supported maritime traffic through the construction of commercial ports and protected low-lying coasts with the creation of structures similar to breakwaters… Since the mid-20th century, however, ocean development has ramped up, and produced both positive and negative results," Bugnot adds in the release.

According to the study, the extent of ocean modified by man-made construction is, proportion-wise, not only comparable to the extent of urbanised land, but also greater than the area of some global natural marine habitats like mangrove forests and seagrass beds. Here is a look at some more interesting findings and figures from the study.

Plethora of infrastructure: For the study, Bugnot and her co-researchers from other local and international universities tapped into data from a variety of sector-specific individual resources that looked at a wide range of marine infrastructure. This included gas and oil rigs, sub-sea pipelines, wind farms, telecommunications cables, wave and tidal farms, aquaculture, commercial ports, tunnels and bridges, recreational marinas, breakwaters and artificial reefs.

32,000 square kilometres: The physical footprint of built structures worldwide as of 2018 amounts to approximately 0.008% of the ocean. This might seem small, but when this estimate is calculated as the area modified including “flow-on effects to surrounding areas"—for example, due to changes in water flow and pollution—the footprint is actually 2 million square kilometres, or over 0.5 percent of the ocean.

A map showing the physical footprint of marine construction globally, in square kilometres. Credit: Bugnot et al., 'Current and projected global extent of marine built structures', Nature Sustainability.

39,400 square kilometres: This physical footprint is projected to grow even further—by almost 23% to almost 40,000 square kilometres—by 2028. According to the study, construction will continue to “sprawl into the ocean for the foreseeable future". As per the news release, the researchers attribute this expansion to people’s increasing need for defences against coastal erosion and inundation due to sea level rise and climate change, as well as for energy extraction, recreation and transportation needs.

50-70%: This is the projected increase in infrastructure for power, aquaculture, cables and tunnels by 2028. Bugnot says the numbers around future expansion “are alarming". “Yet 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," she says in the release.

Ecological ramifications: As the findings show, these constructions around the world also come at a significant ecological cost to the seascape. For example, wind farms can cause noise pollution within a 5.5-km radius around each farm. Similarly, noise pollution from commercial ports can affect a radius of up to 20 km. The paper explains how some of these constructions have produced significant environmental benefits, but when these are “poorly regulated", they could lead to habitat degradation and losses in ocean wilderness.