What are the Impacts of Sea Level Change?

Broad Impacts of Sea Level Rise

There are many factors that influence the impacts of sea level rise on coastal communities. Diversity in coastal landscapes and environments, social and economic factors, and coastal development all play a role. Together, these factors shape how sea level rise impacts are felt in different locations and by different communities.

Direct impacts from sea level rise include increases in flooding, coastal erosion, saltwater intrusion, elevated groundwater, and landscape changes. Building on these are what’s known as cascading impacts. These happen because of the direct impacts and include infrastructure and property damage, health risks, economic challenges, social and cultural changes, and habitat loss.

An introduction to each impact is provided below, but more information can be found in the IPCC Sixth Assessment Report Working Group II: Impacts, Adaptations, and Vulnerability. A two-page summary version can be found here.

Flooding: Flooding, especially during high tides and storms, is one of the most immediate impacts of sea level rise for many communities. Flooding can damage homes, businesses, and infrastructure, and potentially displace people or result in health risks.

Erosion: A naturally occurring process, erosion results in the breaking down of land over time. Rising sea levels can exacerbate coastal erosion as the water reaches higher or further inland. This can impact natural habitats and lead to the loss of land and undermine property and infrastructure.

Saltwater Intrusion: Below ground, saltwater can seep into freshwater aquifers as sea levels rise, a process known as saltwater intrusion. If the saltwater mixes with the fresh groundwater, it makes it unusable for drinking and agriculture leading to potential health risks and economic impacts. Above ground, overland flooding and saltwater inundation can result in loss of cropland and forestland along coasts, due to soil salinization (reducing crop and tree growth) and marsh migration (frequently or permanently flooded cropland).

Elevated Groundwater: Tied to saltwater intrusion, rising sea levels also cause groundwater to rise. The elevation of groundwater can lead to increased rainfall runoff and compromised underground infrastructure, such as public utilities, septic systems, and structural foundations. Higher groundwater levels can also lead to water during storms being unable to drain away from homes and businesses.

Landscape Change: Elevated groundwater, along with increased flooding and erosion, will drive a reshaping of many coasts. Beaches and tidal wetlands, some of the environments at greatest risk, may move inland if space is available or they will disappear underwater. Flexibility of the landscape is tied to human development along the coastline. This development can limit where environments can move, or they can provide restoration opportunities expanding coastal environments.

Infrastructure Damage: Sea level rise threatens vital infrastructure that moves people and goods, powers homes and businesses, and delivers public services. Infrastructure along the coast such as roads, bridges, sewage systems, and power plants may be damaged due to flooding, coastal erosion, and saltwater intrusion, leading to significant economic costs, disruptions to daily life, and health risks.

Health Risks: Flooding and infrastructure damage can lead to public health risks, including exposure to contaminated water and the spread of waterborne diseases. Flooding can also increase risk for mold in homes. Water and electricity outages due to infrastructure damage or failure can also delay or deprive residents’ access to refrigerated medication, medical devices, clean drinking water, air conditioning or heat, and delay or prevent medical treatments.

Economic Impacts: Impacts from worsening coastal hazards can ripple across many economic sectors. Local economies, particularly those that rely on coastal and marine activities such as tourism, fishing, and shipping, may suffer from a change in the availability of resources and potential damage to port infrastructure. Additionally, more frequent or worse coastal hazards can alter the insurance market, impacting home and business owners.

Social and Cultural Impacts: The impacts of sea level rise are not the same for everyone. Disparities in wealth, economic and educational opportunities, infrastructure quality, and investments in flood protection all contribute to different experiences of impacts for coastal residents, with some communities, often those at a lower income level, at higher risk. Additionally, for cultures that have deep ties to the ocean, mounting changes could result in the loss of cultural practices and heritage sites.

Loss of Habitats: Coastal and marine ecosystems, which provide vital services such as storm protection, biodiversity, and fisheries, can be degraded or lost entirely. Saltwater reaching further inland can expose coastal plants to high amounts of salt, which can damage or kill non-salt tolerant plants. This causes a ripple effect, influencing the entire ecosystem. Some ecosystems have an ability to adapt and migrate inland, but are limited by human development and how quickly changes in sea level are happening.