Rise in sea level effects

An average sea level rise of 10 cm by 2030 and half a meter by the end of the next century may not sound like much. However, half of humanity lives in coastal areas around the world. Many of them living below poverty line. For people living in these areas, even a fraction of a meter rise in sea level can greatly exacerbate their problems.

The particularly endangered areas include large river delta areas, such as Bangladesh; secondly, areas in the immediate vicinity of sea level where coastal protection measures are already in place, such as the Netherlands; and third, small, low-lying islands in the Pacific and other oceans.

In Bangladesh about ten percent of the country’s habitable area (with a population of about six million) would be lost with half meters of sea-level rise and about twenty percent (for a population of about 15 million) would be lost in a 1 m rise.

Sea level rise estimates by 2050 are about 1 m (composed of 70 cm due to subsidence due to earthworks and groundwater abstraction and 30 cm due to global warming effects ) and almost 2 m by 2100 (1.2 m due of subsidence of and 70 cm due to global warming).

In our example of Bangladesh, 85 % of the country’s population depends on farming for their livelihood. Many of these people are living below the poverty line. But land loss is not the only impact of sea-level rise. Bangladesh is extremely vulnerable to storm surge damage. Bangladesh is hit by at least one major Cyclone each year on average.

The November 1970 storm surge is probably the world’s largest recent natural disaster; It is estimated that it caused the death of more than a quarter of a million people. More than 100,000, are believed to have lost their lives in a similar storm in April 1991. Even a small rise in sea level increases the region’s vulnerability to such storms.

The rise in sea level has an additional impact on the productivity of agricultural land; that is, the intrusion of salt water into fresh groundwater resources. At present, the salt water is estimated to extend seasonally 150 km inland in parts of Bangladesh. The area affected by saline intrusion could increase significantly, although, as climate change is also likely to bring increased monsoon rainfall, some of the saline incursion may be mitigated.

What possible responses can Bangladesh provide to these likely future problems? During the currently anticipated timeframe for change, it is expected that the fishing industry will be able to relocate and respond flexibly to changing fishing areas and changing conditions. It is less easy to see what the populations of affected agricultural areas can do to resettle or adapt. It is clear that very careful investigation and treatment of all aspects of the problem is required.

The amount of sediment and how it is used can have a major impact on the elevation of land affected by sea level rise. Therefore, careful management is required both upstream and in the delta itself; Groundwater and marine protection must also be carefully managed if relief from the effects of sea-level rise is to be achieved.

A similar situation exists in the Nile Delta in Egypt. The likely sea-level rise this century is due to local subsidence and global warming in the same manner as in Bangladesh: about 1 m by 2050 and 2 m by 2100. About twelve percent of the country arable land, with a population of over 7 million people would be affected by a 1 m rise in sea level.

Extensive sand dunes offer some protection from the sea, but only up to half a meter of sea level rise. For example, several large and low-lying alluvial plains are distributed along the east coast of China. A sea level rise of just half a meter would flood an area of ​​around 40,000 km2 (roughly the area of ​​the Netherlands), which is currently home to more than thirty million people.

A particularly intensively studied delta is the Mississippi Delta in North America. These studies underscore the fact that human activities and industry are already exacerbating the potential problems of rising sea levels due to global warming. Due to river management, the river supplies little sediment to the delta to counteract settlements caused by long-term movements of the earth’s crust. In addition, the construction of canals and dikes has prevented the entry of sediments from the ocean.

Let us now turn to the Netherlands, a country more than half of which is made up of coastal areas. Lowlands, mostly below current sea level. It is one of the most densely populated areas in the world; Eight of the region’s fourteen million inhabitants live in major cities such as Rotterdam, The Hague, and Amsterdam. An ingenious system of around 400 km of dikes and coastal dunes built over many years protects it from the sea. Rather than creating solid bulwarks, more recent methods of protection use the effects of various forces (tides, currents, waves, wind, and gravity) on the sand and sediments to create a stable barrier against the sea.

Similar guidelines are recommended for protecting the Norfolk coast in eastern England. Protecting against sea level rise over the next century will not require new technologies. Dikes and sand dunes need to be raised; Additional pumping will also be necessary to combat saltwater intrusion into freshwater aquifers. It is estimated that protecting against a sea level rise of 1 m would require spending around twelve billion dollars (US).

The third type of particularly vulnerable area is the small and humble islands. Half a million people live on archipelagos build of small islands and coral atolls, such as the Maldives in the Indian Ocean, which are made up of 1190 individual islands. Pacific islands lie almost entirely within, 3 m above sea level. A half-meter or more rise in sea level would significantly reduce its territories (some would have to be abandoned) and remove up to fifty percent of its groundwater.

Many cities in the world are close to sea level and are increasingly affected by subsidence due to groundwater abstraction. Sea level rise will exacerbate this problem. There are no technical difficulties for most cities to solve these problems, but the cost of doing so must be included in when calculating the impact of global warming. So far, when considering the effects of sea level rise, we have looked at places with dense populations that have large impacts on people.There are also significant areas where few people live.

Wetlands and mangroves of the world currently cover an area of ​​about million square kilometers. They contain a lot of biodiversity and their biological productivity is equal to or greater than that of any other natural or agricultural system. Such areas can adapt to the slow rise in sea levels , but there is no evidence that they can keep up with a rate of rise in of more than about 2 mm per year, 20 cm per century.

Therefore, what will tend to happen is that the wetland will expand inland, sometimes resulting in loss of good agricultural land. construction, erosion of the seaward wetland boundaries is more likely to result in the loss of wetland areas. Coastal wetlands are currently being lost at a rate of 0.5 to 1.5% per year.

Sea level rise due to climate change would further aggravate this loss. Global warming is not the only reason for sea level rise but will likely exacerbate impacts from other environmental factors.

Careful management of human activities in affected areas can go a long way to mitigating likely impacts, but significant negative impacts will remain.

The number of people worldwide affected by the floods due to storm surges is now estimated at around forty million. A 40 cm rise in sea level in the 2080s is estimated to quadruple that number, a number that could be halved if the coast were protected.

Since, as we have seen, it takes the ocean, centuries to adapt to a rise in surface temperature, the longer-term effects of sea-level rise also need to be emphasized. Even if concentrations of greenhouse gases in the atmosphere were to stabilize to halt anthropogenic climate change, sea levels will continue to rise for many centuries while the entire ocean adapts to the new climate.