Rising sea levels – a growing danger

Rising sea levels are already impacting on people and the environment and present a serious and urgent policy problem, Orrin Pilkey writes.

With the world warming from anthropogenic climate change, sea levels are rising at an ever-accelerating rate. One of the strongest visual indications of this, as most coastal dwellers would attest to, are the bands of dead trees emerging along coastal plain margins, a phenomenon caused by saltwater intrusion.

Other indications are ‘sunny day floods’ caused by high tides, often pushed even higher on windless days by sea level rise. King tides, the highest of these floods, can be particularly damaging, causing saltwater corrosion of vehicles, pipes, and guardrails, sewer overflows, driving inconveniences, and significant falls in property prices.

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One example of those in most immediate trouble from sea levels rising are those who live in the small Native American coastal villages of northern Alaska, as well as Siberia and northern Canada. Just like everywhere else, sea levels are rising above the Arctic Circle, creating climate impacts for these villages that, without rapid action, will soon be replicated across the globe.

Sea level rise combines with additional problems in these communities, such as melting permafrost, which causes extensive loosening of sand, and the loss of protective sea ice that normally covers the surf zone during the autumn and winter storm season. Together, these are creating rapid shoreline erosion where none existed just a decade or two ago.

In years gone by, Alaska’s surf zone would freeze by early September, allowing shorelines some protection, but now it doesn’t freeze until November or later, exposing shorelines to storm waves for at least two more months of potential erosion.

In many communities affected by sea level rise, a large and costly effort to hold the shorelines in place in the face of a rising sea is primarily done to protect development. The problem is that hard structures such as seawalls do not address the processes that cause shoreline erosion, and erosion continues after wall placement.

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Seawalls can effectively hold back sea level rise for a while, but the price is eventual loss of the beach, with dire consequences. Along with natural loss, there is an economic price to pay. When coastal communities lose their beaches, tourist dollars begin to dry up.

This presents a difficult policy dilemma. While for some, seawalls have been the solution of choice, for others, they are now prohibited – although exceptions are often made – and instead, beach replenishment is the most common approach to shoreline stabilisation. This method, which usually involves dredging offshore sand to pump up to the beach, is costly, requires repeated application, and is disastrous to beach and nearshore ecosystems.

On average, replenished beaches last less than five years, and are expensive to replace. Costs of beach replenishment in the United States, for instance, often called ‘nourishment’, are at least a million dollars per project per mile of beach. Single nourishment projects have even been known to cost as much as $20 million per mile.

Without a more sustainable policy solution, all kinds of infrastructure close to the sea will be profoundly impacted. Ocean ports will not only need to raise docks to accommodate sea level rise, but the extensive freight yards where containers and other cargo are stored must also be raised.

Any global response to the sea level problem will likely be disruptive to international commerce and the military, but it must be done. At a high cost, two docks have already been raised at an American naval base, in anticipation of sea level rise. Moreover, hundreds of wastewater plants of cities large and small are typically located near the sea to facilitate gravitational flow and will need to be moved back to higher elevations too.

However, the costs of inaction would be even greater. A large number of oil refineries and oil and water storage facilities are also located at low elevations and simply must be moved. Another example, and perhaps the most threatening for nearby populations, is the high number of nuclear power plants in the range of potential sea level rise.

On top of it all, sea level rise will create millions of climate change refugees. In the face of rising sea levels, retreat from affected areas is inevitable, leading to millions of people in need of new, safer places to live. Estimates of the number of climate refugees displaced every year are approaching 25 million, with a potential number of 140 million worldwide by 2050.

Without a serious policy framework to deal with this issue, the costs will be great, and policymakers must come together to create a global response. If they can’t, or won’t, then they must be prepared for the dire consequences of inaction.