Future ‘ocean cities’ need green engineering above and below the waterline



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Artificial islands can cause huge environmental issues for coastlines.
The Forest City Project

Katherine Dafforn, UNSW; Ana Bugnot, UNSW; Eliza Heery, National University of Singapore, and Mariana Mayer-Pinto, UNSW

Population growth has seen skylines creep ever higher and entire cities rise from ocean depths. The latest “ocean city” is the Chinese-developed Forest City project. By 2045, four artificial islands in Malaysia will cover 14km² of ocean (an area larger than 10,000 Olympic swimming pools), and support 700,000 residents.

Often overlooked, however, is the damage that artificial islands can cause to vital seafloor ecosystems. But it doesn’t have to be this way. If proper planning and science are integrated, we can develop the design strategies that will help build the “blue-green” ocean cities of tomorrow.




Read more:
Concrete coastlines: it’s time to tackle our marine ‘urban sprawl’


Colonising the ocean frontier

Ever growing numbers of human-made structures are occupying our oceans. Cities built on artificial islands in the ocean are providing a solution for urban planners trying to manage the population squeeze.

And yet, so-called “ocean sprawl” dates as far back as Ancient Egypt. Over the past few centuries, artificial islands have been built through land reclamation. Land reclamation is the process of creating new land from existing water bodies.

Atlantis, The Palm Hotel in Dubai, United Arab Emirates is built on an entirely artificial island.
Shutterstock

The Netherlands, for instance, has been draining lakes and expanding its coastline to fight the advance of the sea since the 1500s. The Dutch actually built one of the first and largest artificial islands, which is now home to some 400,000 people. Japan’s third-busiest airport, the Kansai International Airport, was built on an artificial island in 1994. China has also been building into the oceans, reclaiming more than 13,000km² of seafloor and an estimated 65% of tidal habitat since the 1950s.

The artificial Eden Island in Mahe, Seychelles.
from http://www.shutterstock.com

Using Google maps, we were able to identify more than 450 artificial islands around the world, including the famous Palm Islands of Dubai. These are often celebrated as engineering marvels, but at what cost to the marine environment?

We can’t ignore what lies beneath

Marine habitats have always been essential for human life in coastal regions. They provide food, building and crafting materials, and less-known services such as coastal protection, nutrient cycling and pollution filtration.

One of the World Map islands in Dubai, United Arab Emirates.
Shutterstock

The creation of artificial islands causes large changes to the seabed by permanently smothering local habitats. In many parts of the world, existing habitats provide the foundation for artificial island construction. For instance, artificial islands in the tropics are often built directly on top of coral reefs. This leads to considerable destruction of already threatened ecosystems.

Land reclamation also impacts nearby habitats that are particularly sensitive to murky waters, such as coral reefs and seagrass beds. In Singapore, land reclamation is associated with coral reef decline due to sedimentation and resulting light reductions. Singapore has lost nearly 45% of the country’s intertidal reef flats and almost 40% of intertidal mudflats.

When the ecological, economic, and social value of marine habitats are considered, artificial islands and ocean sprawl seem to be indulgences that we cannot afford. The effects would be akin to the suburban sprawl of the 20th century. To avoid this cost, we need to address the complexities of the underwater world in urban planning and development.

“Blue urbanism”

In his book Blue Urbanism, Timothy Beatley calls for urban planners to consider and value ocean ecosystems. He argues that we need to recognise the psychological value of human connections to blue space, and extend green practices on land into marine environments. While some artificial island developments such as the Forest City project are touted as “eco-cities”, more could be done both to minimise impacts below the waterline and integrate underwater environments into city life.

Why not combine a “Forest City” with the principles of a “Sponge City”? While native plantings in a forest city could help to reduce air pollution, sponge cities seek to “absorb” and reuse rainwater, thus reducing pollution entering the oceans through stormwater runoff. Around artificial islands, developers could also embrace the water filtration powerhouse of the oceans: active oyster reefs.

The location of future constructions should also be carefully evaluated to ensure the preservation of important marine habitats. Artificial islands have the potential to create fragmented seascapes, but with careful spatial planning and smart designs, they could create corridors for some climate migrants or those threatened species most at risk from habitat loss.

The ConversationDesigns based on ecological principles can reduce the impacts of artificial islands on natural habitats. However, applications of “blue-green” infrastructure remain largely untested at large scales. New designs, building strategies and spatial planning that integrate seascapes and landscapes are an opportunity for both “smarter” cities and experimentation for the development of successful blue-green technologies.

Katherine Dafforn, Senior Research Associate in Marine Ecology, UNSW; Ana Bugnot, Research Associate, UNSW; Eliza Heery, Research Fellow in Marine Ecology, National University of Singapore, and Mariana Mayer-Pinto, Senior Research Associate in marine ecology, UNSW

This article was originally published on The Conversation. Read the original article.

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The Sydney Barrier Reef: engineering a natural defence against future storms


Rob Roggema, University of Technology Sydney

The risk of more severe storms and cyclones in the highly urbanised coastal areas of Newcastle, Sydney and Wollongong might not be acute, but it is a real future threat with the further warming of the southern Pacific Ocean. One day a major storm – whether an East Coast Low or even a cyclone – could hit Sydney. The Conversation

With higher ocean temperatures killing and bleaching coral along the Great Barrier Reef to the north, we could also imagine where the right temperatures for a coral reef would be in a warmer climate. Most probably, this would be closer to the limits of the low latitudes, hence in front of the Sydney metro area.

We should then consider whether it is possible to help engineer a natural defence against storms, a barrier reef, should warming oceans make conditions suitable here.

Ocean warming trend is clear

The oceans are clearly warming at an alarming rate, with the unprecedented extent and intensity of coral bleaching events a marker of rising temperatures. After the 2016-2017 summer, coral bleaching affected two-thirds of the Great Barrier Reef.

On the other side of the Pacific, sea surface temperatures off Peru’s northern coast have risen 5-6℃ degrees above normal. Beneath the ocean surface, the warming trend is consistent too.

The East Australian Current keeps the waters around Lord Howe Island warm enough to sustain Australia’s southernmost coral reef. The waters off Sydney are just a degree or two cooler.

With the East Australian Current now extending further south, the warming of these south-eastern coastal waters might be enough in a couple of decades for Nemo to swim in reality under Sydney Harbour Bridge.

This shift in ocean temperatures is expected to drive strong storms and inland floods, according to meteorologists.

On top of this, when we plot a series of maps since 1997 of cyclone tracks across the Pacific, it shows a slight shift to more southern routes. These cyclones occur only in the Tasman Sea and way out from the coast, but, still, there is a tendency to move further south. The northern part of New Zealand recently experienced the impacts this could have.

Think big to prepare for a big storm

If we would like to prevent what Sandy did to New York, we need to think big.

If we don’t want a storm surge entering Parramatta River, flooding the low-lying areas along the peninsulas, if we don’t want flash-flooding events as result of river discharges, if we don’t want our beaches to be washed away, if we want to keep our property along the water, and if we want to save lives, we’d better prepare to counter these potential events through anticipating their occurrence.

The coast is the first point where a storm impacts the city. Building higher and stronger dams have proven to be counterproductive. Once the dam breaks or overflows the damage is huge. Instead we should use the self-regenerating defensive powers nature offers us.

Thinking big, we could design a “Sydney Barrier Reef”, which allows nature to regenerate and create a strong and valuable coast.

The first 30-40 kilometres of the Pacific plateau is shallow enough to establish an artificial reef. The foundations of this new Sydney Barrier Reef could consist of a series of concrete, iron or wooden structures, placed on the continental shelf, just beneath the water surface. Intelligently composed to allow the ocean to bring plants, fish and sand to attach to those structures, it would then start to grow as the base for new coral.

This idea has not been tested for the Sydney continental flat yet. But in other parts of the world experiments with artificial reefs seem promising. At various sites, ships, metro carriages and trains seem to be working as the basis for marine life to create a new underworld habitat

The Sydney Barrier Reef will have the following advantages:

  1. Over decades a natural reef will grow. Coral will develop and a new ecosystem will emerge.

  2. This reef will protect the coast and create new sandbanks, shallow areas and eventually barrier islands, as the Great Barrier Reef has done.

  3. It will increase the beach area, because the conditions behind the reef will allow sediments to settle.

  4. It creates new surfing conditions as a result of the sandbanks.

  5. It will protect Sydney from the most severe storm surges as it breaks the surge.

  6. It will present a new tourist attraction of international allure.

Let’s create a pilot project as a test. Let’s start to design and model the pilot to investigate what happens in this particular location. Let’s simulate the increase of temperature over time and model the impact of a cyclone.

Let’s create, so when Sandy hits Sydney, we will be better protected.

Rob Roggema, Professor of Sustainable Urban Environments, University of Technology Sydney

This article was originally published on The Conversation. Read the original article.