Our directory of things of interest

University Directory

Losing Louisiana: the sinking state

Studies show that Louisiana is sinking  at a rate of eight to ten millimetres per year Studies show that Louisiana is sinking at a rate of eight to ten millimetres per year Pierre Jean Durieu
08 Aug
The southern US state is sinking twice as fast as previously thought, with human mismanagement of its coast being held largely to blame

Scientists have long known that Louisiana is sinking. Its southern coast is widely regarded as being among the fastest-disappearing areas in the world and over the past 50 years the state has lost valuable wetlands equal to ten times the size of New York City. Now, research from Tulane University has confirmed that the Pelican State’s loss of landmass is happening at the rate of what was previously considered to be the worst-case scenario.

Jaap Nienhuis, postdoctoral fellow in environmental science and lead author of the research was shocked by the findings. ‘Previous studies that were based on less data had rates at somewhere between three to four millimetres per year, with worst-case scenarios of about eight to ten millimetres per year,’ he explains. ‘We found that nine millimetres per year is actually the average.’

The new total comes from readings taken by surface-elevation tables – mechanical levelling devices used to measure relative sediment elevation changes – in 274 stations around the coast.

The main reason for the loss is the natural process of sediment compaction. Over time, wetland soils become more compressed, leaving them with less air and water between sediment. This means they form thinner layers. The compaction is usually offset by the build up of more sediment from the floods of the Mississippi river. However, this process has been stopped by the construction of dams and levees. ‘We’re keeping a large part of the Mississippi River sand and mud behind all the dams further upstream,’ says Nienhuis, ‘and the rest is being flushed between the levees straight into the sea.’ The problem is being exacerbated further by oil, gas and groundwater extraction, which causes compression at deeper layers underground.

As well as sediment loss, the sea level is rising, swallowing the land by 3mm per year. Together the dual pressures mean the state is losing a yearly average of 12mm of coastal wetlands, regions that often serve as vital ecosystems, agricultural land, or buffers for storms.

This was published in the August 2017 edition of Geographical magazine.

Related items

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.

Subscribe to Geographical!

Adventure Canada


Aberystwyth University University of Greenwich The University of Winchester




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • National Clean Air Day
    For National Clean Air Day, Geographical brings together stories about air pollution and the kind of solutions needed to tackle it ...
    The Air That We Breathe
    Cities the world over are struggling to improve air quality as scandals surrounding diesel car emissions come to light and the huge health costs of po...
    Hung out to dry
    Wetlands are vital storehouses of biodiversity and important bulwarks against the effects of climate change, while also providing livelihoods for mill...
    When the wind blows
    With 1,200 wind turbines due to be built in the UK this year, Mark Rowe explores the continuing controversy surrounding wind power and discusses the e...
    Mexico City: boom town
    Twenty years ago, Mexico City was considered the ultimate urban disaster. But, recent political and economic reforms have transformed it into a hub of...


NEVER MISS A STORY - Follow Geographical on Social

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in PLACES...


In this extract from his new book, Tides, mountain climber…


New data from the World Health Organization reveals that nine…


In the wake of the water crisis in Flint, Michigan,…


Benjamin Hennig maps out the global production and distribution levels…


Millions of Americans are living in areas at high-risk of…


New interactive maps combine precipitation and temperature to show climate…


Public transport in India could be on the verge of…


To retrace the route of the fur voyageurs on the waterways…


IPCC Cities and Climate Change Conference: Alberta host dresses non-renewable…


Increased carbon dioxide is affecting freshwater ecosystems


The latest laser scanning technology reveals new insights into the…


Deforestation is having an unexpected effect in the Amazon: fewer…


The iconic Douglas fir tree, familiar to fans of the…


Rocky Mountain forests are not regenerating after wildfires


Cape Town is edging closer to ‘Day Zero’, the long-feared…


Ongoing restoration projects are breathing new life into Florida’s Everglades


Despite protests, an experimental pedestrianisation system is proving to be…


National Archives map historian, Rose Mitchell, highlights some of the…


An expedition into the Jordanian desert is helping teachers and…


Trivia fans take note, Mount Hope in the British Antarctic…