Sea level rise could put displace millions of people. We aren’t ready for it.

Sea Level Rise Article Guide

Next Generation Science Standards

• MS-ESS3-3. Apply scientific principles to design a method for monitoring and minimizing a human impact on the environment.

Miami, New Orleans, and New York City are three of America’s most populous and culturally significant cities. Yet all three could be under water by the end of this century.  Since 1990, global average sea level has risen about 7-8 inches, and three of those inches have occurred since 1993. The ocean could continue to rise an additional 3-7 inches by 2030, and even as much as 8 feet by the end of this century. Sea level rise of this extent would damage coastal habitat, flood coastal cities, and worsen the effects of large storms, like hurricanes.

Feeling the heat

Global sea levels are rising is because of two main factors. Land ice, such as the glaciers and ice sheets of Greenland and Antarctica, are melting more quickly than in the past (Image 1). While it’s normal for land ice to melt during the summer, steadily higher temperatures have meant for later winters and earlier springs. This longer summer melting period, combined with less snowfall than in the past, have dramatically reduced the amount of land ice. It’s important to remember that sea ice melting does not affect sea level, but it’s the increase in land ice that falls into the ocean that is causing the water to rise.

The second reason is thermal expansion. Changes in air temperature affect the density of the sea, warm water takes up more volume than cold water.  When the air temperature rises, the sea becomes less dense and expands, causing the sea levels to rise. So as the atmosphere continues to warm, the ocean will continue to absorb that heat, and the sea levels will keep rising faster and higher for many centuries.

Treading water

Almost 40 percent of the US population lives in relatively fairly crowded coastal areas, where rising sea levels can flood streets, erode shorelines, and create hazards during and after storms. Over half of the Earth’s population live within 125 miles of a coastline, and 8 of the globe’s ten biggest cities are by a coast, according to the U.N. Atlas of the Oceans. The US state of Florida alone has 2.1 million people living below sea level.

Higher sea levels mean that deadly and dangerous storm surges, or the rise in seawater level because of a storm, will push farther inland than in the past. When Hurricane Sandy struck New York City in 2012, subway tunnels flooded and there were massive power outages, exacerbated because the seas surrounding the city have risen one foot within the past century. Even when storms aren’t happening, sea level rise will cause more nuisance flooding (Image 3), when abnormally high tides can impact infrastructure, like roads, bridges, subways, power plants, sewage treatment plants, landfills, and so on.

People need all of these things in their everyday lives, so the flooding of these structures threatens jobs, businesses, health, safety, and economic well-being. Even today, homes are losing value as more buyers become aware of these risks. Charleston, SC homes have lost $266 million in value since 2005 because of coastal flooding and expectations of still higher seas.

And it’s not just an everyday nuisance or something that will make you lose money on your house.  Rising sea levels could also cause saltwater to seep into groundwater, making tap water undrinkable for people and harmful for aquatic animals and plan. Sea level rise may also damage or completely destroy low-lying, coastal ecosystems, like wetlands and mangroves. Increased, unchecked coastal development can worsen the vulnerability of these ecosystems to sea level rise because building along the coast often enhances erosion and prevents wetlands from moving inland against rising seas or acting as a buffer to coastal communities. Coastal Louisiana has already lost around 2000 square miles of coastal wetlands due to altering the Mississippi River’s sediment and extracting oil and gas.

Poorer communities or minorities that live near the coast are the most vulnerable to these impacts because they have fewer resources to adapt or opportunities to leave. Indigenous communities in states like Alaska, Washington, and Louisiana may lose their homes in the future because of rising sea levels, and some, such as the Biloxi-Chitimacha-Choctaw Indians and the Quinault Indian Nation, are already planning to resettle.

A wetter world

So how we adapt to a world of rising seas? City planners and scientists generally have three options. The first is to build infrastructure like sea walls to try to hold the water back or to divert water flow. Other man-made barriers tools include sandbags to fix the shoreline, levees, or large gates or locks. These barriers could protect a lot of land and people; however, they are often expensive, some could potentially damage the environment, and many are short-term solutions.   

Another solution is to create “living shorelines” such as wetlands, marshes, and rocky shores to act as natural buffers. Restoring these coastal ecosystems can improve estuary health, protect shorelines from floods and erosion, and slow down approaching water. These projects are beneficial to everyone, as wetlands create cleaner waters, capture carbon from the atmosphere, create important habitat, and provide space for recreation. However, these projects are timely and require a lot of work, and there are a lot of challenges as more and more people build houses along the coast.

Despite these options leaders, community members also should become involved in helping to adapt to sea level rise. It’s essential that community members understand these complex human and natural systems, including the science and impacts of sea level rise and the uncertainty in planning for the future.

There are education projects happening around the country that help citizens become involved in projects that can help scientists and city planners with adaptation efforts. The University of Southern California Sea Grant’s Urban Tides Community Science Initiative records tidal lines, beach erosion, and coastal flooding. The public takes pictures and documents tides during winter storms or king tides, which offer a glimpse into what future sea levels will look like. Then the public uploads the pictures into an online database, which helps scientists confirm their own data, and the photos pinpoint areas to decision makers that need to be a priority for adaptation planning.

Humans are going to have to adapt to sea level rise no matter what. That said, lowering our carbon footprint can still make a huge difference. If governments around the world work together to dramatically cut fossil fuel emissions, we could reduce the amount of sea level rise by 6-20 inches in 2100. The David Suzuki Foundation lists some really great things you can do to help reduce emissions, both in your own life and at the larger scale, such as eating less meat, advocating for a carbon tax, and reducing your use of plastic: https://davidsuzuki.org/what-you-can-do/top-10-ways-can-stop-climate-change/.

Learn more:

An educated and engaged public is really the key to help communities best adapt to rising sea levels. Here are just some of the online resources that will help you better understand this issue:

• USC Urban Tides Community Science Initiative
• US Climate Resilience Toolkit: Sea Level Rise
• EPA Sea Level Rise
• UCAR Center for Science Education: Rising Sea Level
• NOAA National Ocean Service: Educational Resources on SLR
• NOAA Digital Coast: Sea Level Rise Viewer
• Other sea level rise adaptation plans city planners consider