The area of sea around the world which is affected or modified by construction activity is at least as great as that which has been impacted on land, a new study has found.
Published in Nature Sustainability and led by Dr Ana Bugnot from the University of Sydney and the Sydney Institute of Marine Science, the study was the first in the world to map the impact of construction on ocean and marine environments.
It found that worldwide, as much as 32,000 square kilometres of ocean had been impacted by man-made built structures in 2018 – equating to 0.008 percent of the overall ocean area.
This includes areas which have been 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.
By 2028, meanwhile, the = footprint of built structures on marine environments was expected to reach 39,400 sqm.
The extent of ocean modified by human construction is comparable to the extent of urbanised land – relatively speaking – and it is greater than the global area of some natural marine habitats, such as mangrove forests and seagrass beds.
When taking into the account flow-on effects to surrounding areas – for example, changes in water flow and pollution – the footprint is even bigger: two million square kilometres, or over 0.5 percent of the ocean.
Moreover, as shown below the research demonstrated that coastal habitats – among the most productive habitats in the ocean, are the most impacted by marine construction.
This includes areas of the coast of many Asia Pacific Countries as well as in the Arctic north of Russia and in and around both coastlines of the Americas.
Study co-author Dr Mariana Mayer Pinto from UNSW Science said the importance of understanding the impact of construction upon marine environments should not be underestimated.
“On land, the expansion of urban areas – which is one of the main drivers of biodiversity loss – is well quantified, but so far, we’ve had very little idea of how much the marine environment had been modified by construction,” she said.
“Such construction can cause severe environmental impacts not only directly – through the loss of habitats where construction is taking place – but also indirectly, through the associated activities with these structures, such as pollution.”
Whilst acknowledging that development in ocean environments is not new – structures such as commercial ports and protection of low-lying areas through facilities similar to modern breakwaters has been going on since before 2000 BC – Bugnot says the pace of oceanic development has ramped up since the middle of last century.
This, she says, has had both beneficial and detrimental results.
Creation of artificial reefs, for example, have been used as a sacrificial habitat’ to drive tourism and deter fishing, but this infrastructure can also impact sensitive natural habitats like seagrasses, mudflats and saltmarshes, consequently affecting water quality
Moreover, oceanic related construction is expected to increase amid a growing need to for defences against coastal erosion and inundation due to sea level rise and climate change, as well as transportation, energy extraction, and recreation needs.
For some forms of infrastructure, Bugnot says the built structures footprint could grow by between 50 and 70 percent between 2018 and 2028 – a number she says is an underestimate on account of the dearth of ocean development due to poor regulation in many parts of the world.
This includes infrastructure such as cables and tunnels used for power and aquaculture.
Despite its overall impact, Mayer Pinto cautions against any overly negative view of marine based construction and says the costs of this need to be weighted against benefits which such structures deliver.
Facilities for renewable energy (such as offshore wind), for example, may have impacts upon the marine environment yet may be preferable from an environmental viewpoint compared with extraction of fossil fuels.
In such cases, what are needed are not prohibitions against such activities but rather evidence-based management to minimise potential negative side effects on the marine environment, such as eco-engineering approaches and/or strict policies on where to build these structures.
On this score, she points to a framework which UNSW scientists released last year to help guide the management and development of coastal infrastructure in a sustainable manner.
Moreover, Bugnot says better management is needed for marine environments.
Initiatives such as the EU Marine Strategy Framework Directive were a good start.
Report co-author Professor Emma Johnston, UNSW Dean of Science, hopes the study will help to spur global efforts for integrated marine spatial planning, and drive improved data collection.
“Our datasets offer a starting point for a living database that can be updated over time. It will help us create improved estimates of the current physical footprint of marine construction and extent of seascape modified around these structures, and provide important tracking for future developments,” Johnston said.
“We hope it’ll also inform more comprehensive policies that consider the big picture of marine habitat loss – this is particularly important given the lack of incentives to drive ecologically sustainable development on or below the waterline.”