As Climate change accelerates, cities worldwide are increasingly threatened by the alarming rise in sea levels. Currently, The Sea levels are rising faster than expected and could increase by 75 cm to 2 m by 2100, potentially putting the major cities near coastlines in grave danger. Floating cities present a promising adaptation strategy addressing spatial constraints and rising sea levels and harmonizing with marine ecosystems, offering a sustainable way forward for coastal urban areas. This article explores the concept of floating cities and their impact on biodiversity.
Why Floating Cities?
As the atmosphere heats up, the oceans are absorbing more warmth, and the sea levels are rising, further fuelled by melting ice caps. Around 90% of the largest cities in the world are near coastlines (Waterstudio.NL), making them vulnerable to these alarming sea levels. To adapt to changing conditions, engineers and technologists have suggested rethinking the city construction process. Cities have long been pushed into the sea for space, as seen in places like Singapore, where 25% of the city is built on reclaimed land, and Dubai, which has luxury developments on man-made islands. The “aquapreneurs”, as they call themselves, propose Floating Cities as a viable solution to challenges posed by the rising sea levels. Imagine cities like lily pads, floating on water, with buildings that sway with the waves, creating adaptable, resilient communities on oceans thriving in harmony with the Aquatic Biodiversity.
Impact on Biodiversity Due to Floating Cities
Challenges
- Blocking of Sunlight
Floating Cities can block sunlight, limiting solar radiation from reaching the water below. This shading disrupts the surrounding ecosystems by affecting phototrophic organisms essential for the food chain. Research has shown that reduced light exposure leads to lower dissolved oxygen levels underneath these structures, as photosynthesis is diminished in shaded areas. The design of these Floating cities, specifically their size, shape, and orientation, plays a crucial role in the extent of shading. Incorporating skylights or using light-transmissive materials could help mitigate these negative impacts on aquatic biodiversity.
2. Heat Exchanges
The materials used to support Floating Cities can have high heat capacity and conductivity, allowing absorption of heat during the day and releasing it at night. During winter, these structures may also be artificially heated, serving as a heat source for the surrounding water. This heat transfer can affect water temperature and subsequently impact the metabolic rates of aquatic organisms, nutrient cycles, phytoplankton and macrophyte growth, photosynthesis, and dissolved oxygen levels. It is imperative to have effective insulation to minimize the heat transfer to the water.
3. Light and Noise Pollution
Floating Cities bring intensified human activities on the water, which introduces new sources of noise and light pollution affecting the biodiversity of the region. These disturbances can significantly affect ecosystems as many species are highly sensitive to noise and light, impacting their communication, orientation, and reproduction cycles. This disruption can destabilize food webs and aquatic ecosystems. Night-time light pollution can alter fish behavior and disrupt migratory birds. Continuous exposure to noise and sound can even increase the mortality rates of the nearby Biodiversity.
4. Introduction of Non-Indigenous Species
Floating structures can create surfaces that support the attachment of various organisms and provide food and shelter for smaller fish, potentially boosting aquatic biodiversity. If designed well, these structures can enhance water quality by incorporating seaweed to absorb contaminants and promote bivalve growth for natural filtration. Studies have shown that floating platforms can quickly develop vibrant ecosystems, with mussels and fish appearing within a few years. However, careful planning is essential to avoid attracting invasive species or creating ecological traps and focus on promoting native species rather than inadvertently favoring non-indigenous ones.
5. Changes in Migration Patterns
Floating structures can act as physical barriers to the movement of organisms by altering the environmental conditions in a way that would deter species migrations. Activities like a floating Wind farm would generate electric and magnetic fields that can confuse fishes and affect their migrations. Floating Cities would even attract birds and provide space for nests. These cities might act as a good resting space for the migratory birds on-route their travel and in turn can delay or even alter their migration patterns.
Promising Applications
- Biorock Reefs
Biorock is a unique ocean technology that creates a construction material that strengthens over time, self-repairs when damaged, and revitalizes eroded marine ecosystems. This mineral-accretion technology uses electric currents in seawater to crystallize dissolved minerals into heavy limestone coatings that are two to three times stronger than ordinary concrete. Biorock reefs, more affordable than traditional seawalls and breakwaters, have withstood the strongest hurricanes and avoid causing beach erosion. They also help rapidly restore coral reefs, oysters, sea grasses, and other coastal ecosystems that would otherwise struggle to recover. Biorock’s structures can hence enhance the survival of marine organisms, even under extreme temperatures and pollution.
2. 3D Ocean Farming
Floating cities present a potential for the use of 3D ocean farming. This approach requires no external inputs, meaning no fertilizers, nutrients, or freshwater are needed for crop growth. Such crops can help keep oceans clean while also reducing carbon levels. For example, oysters can filter up to 50 gallons of water daily, improving water quality, while kelp can absorb five times more carbon than land-based plants. This carbon absorption is crucial since carbon dioxide is a significant contributor to global warming, as it traps heat in the atmosphere.
The Case of ‘Oceanix’ Floating City
South Korea had signed up for a groundbreaking agreement with Oceanix, supported by the UN’s habitat project, to develop the world’s first Floating City. This project will be situated off the coast of Busan, a city of 3.4 million residents who face the threat of rising sea levels. The city would be designed with a wealth of sustainable technologies, including the innovative use of Biorock to anchor the settlements while simultaneously creating artificial reefs that help regenerate marine ecosystems. The BIG-Bjarke Ingels Group and SAMOO (Samsung Group) are the leading architects behind OCEANIX Busan.
This Floating City will produce its food, fresh water, and energy while generating zero waste through a closed-loop system, while also aiming to implement 3D ocean farming. The design features hexagonal pods that resemble a beehive honeycomb, fitting together for maximum efficiency. Spanning 75,000 acres, it will initially accommodate 10,000 residents, with the potential for more pods to be added over time. The prototype city in Busan is projected to cost around $200 million and will take approximately three years to complete.
To conclude one can say that Floating cities offer a creative solution to urban challenges posed by climate change, especially rising sea levels. But, they bring along both opportunities and challenges for marine ecosystems. The impact on biodiversity, changes in migration patterns, and issues like heat exchange and pollution need to be carefully managed. Innovative technologies, such as Biorock reefs and 3D ocean farming, could help these structures coexist with aquatic environments, enhancing ecosystem health while promoting sustainability. Thoughtful design and conscientious planning are crucial to ensure that floating cities contribute positively to both urban resilience and marine conservation in the face of climate change.
Sources :
de Lima, R.L., de Graaf-van Dinther, R.E. and Boogaard, F.C. (2022) ‘Impacts of floating urbanization on water quality and aquatic ecosystems: A study based on in situ data and observations’, Journal of Water and Climate Change, 13(3), pp. 1185–1203. doi:10.2166/wcc.2022.325.
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