The South China Sea has become a stage for Hong Kong’s dystopic future wherein 1.1 million people, many displaced by a housing crisis, are expected to live on artificial islands within the next 30 years.

Hong Kong’s chief executive, Carrie Lam, outlined a plan for the ambitious geoengineering project in a policy address on Wednesday. Dubbed “Lantau Tomorrow Vision,” it will add 4,200 acres of new land near Lantau Island, Hong Kong’s largest outlying island at the mouth of the Pearl River. The location was selected from a list of several potential sites. Hong Kong’s government has yet to attach a price to the project, but local media have estimated its total cost could reach $63.8 billion (HK$500 billion).

“The vision aims to instil hope among Hong Kong people for economic progress, improve people’s livelihood and meet their housing and career aspirations,” Lam’s address said.

The appeal of more land and housing is understandable. The artificial islands would eventually contain 260,000 to 400,000 residential units, 70 percent of which would be public housing, for 700,000 to 1,100,000 people (15 percent of the population), according to Hong Kong’s government.

Lantau Tomorrow Vision will be Hong Kong’s largest land reclamation project, a process in which new land is created from bodies of water. Building an island out of nothing is no small feat—in Hong Kong, methods have included dredging the seafloor and injecting cement into the seabed. Approximately 6 percent of Hong Kong’s land is reclaimed, and houses 27 percent of its population.

Image: Wikimedia Commons

But environmentalists say the plan may irreversibly damage the surrounding ecosystem. In August, the World Wildlife Fund deemed land reclamation a “last resort” solution to Hong Kong’s housing crisis, urging the government to consult conservationists before plowing ahead. Ecologists predict the islands could eliminate natural fisheries and disrupt ocean and wind currents. Noise pollution from construction could also harm the Chinese white dolphin, a local species whose numbers are already declining.

Another looming consequence is catastrophic flooding due to climate change. Sea levels in Hong Kong are expected to increase more than three feet above 2000 levels by the end of the century, Leung Wing-mo, former assistant director of Hong Kong’s weather monitoring observatory, told the South China Morning Post. Across Hong Kong, Shanghai, and Tianjin, coastal flooding could displace 45 million people if global temperatures enter the realm of worst-case scenarios.

“If you want to minimize the chance of flooding, of course the higher [above sea level] the better,” Gabriel Lau Ngar-cheung, director of the Chinese University of Hong Kong’s Institute of Environment, Energy and Sustainability, said of Lantau Tomorrow Vision to the South China Morning Post. “But of course the cost will be far greater.”

Ringo Mak Wing-hoi, co-founder of the local climate change organization 350 Hong Kong, told the outlet that adapting infrastructure on the islands to resist sea level rise could double project’s total cost.

The risks aren’t solely hypothetical, either. Last month, Typhoon Mangkhut swept through Hong Kong with 107 mile-per-hour winds, and superstorms like it are expected to become more common. Weeks earlier, Typhoon Jebi flooded the runway of Japan’s Kansai International Airport, notably built on reclaimed land, marooning passengers for hours.

Lam’s address claimed the islands would be “smart, green, and resilient to environment and climate,” incorporating renewable energy and advanced waste management techniques. A key tenet of the project is for “conservation to precede development,” though it’s clear that some environmental groups are skeptical of these claims.

Other opposition to the project argues that Lam’s Task Force on Land Supply rushed to approve the proposal which won’t actually serve the public—the first housing units wouldn’t open until 2032, and families are already waiting an average of five years to receive public housing. Furthermore, a 2016 government survey comprised of 7,550 comments found that nearly three quarters of Hong Kong residents were opposed to construction of the islands.

The controversy over Lantau Tomorrow Vision doesn’t negate the fact that solutions are needed to solve Hong Kong’s housing crisis. Already, developers are experimenting with “nano flats,” supertall high rises, and permanent housing on cruise liners.