Our directory of things of interest

Coast Lines

  • Written by  Benjamin Hennig
  • Published in Mapping
Coast Lines
22 Oct
Coasts are a more complex geographical entity than you might believe. Benjamin Hennig maps the world's coasts to learn more

The question about the length of the world’s coastlines is not as easy to answer as it would initially seem. The British mathematician and meteorologist Lewis Fry Richardson was among the first to investigate this phenomenon of the fractal nature of boundary lines in the early twentieth century. The rougher coastlines are, the more of a fractal nature they have and the more difficult it becomes to determine their length since this changes when looking at it using different scales and resolutions.

Richardson’s fellow mathematician, Benoit Mandelbrot, further investigated this phenomenon by looking at the length of the coast of Britain. He explained how the length of a coastline increases the smaller the ruler used for measuring. This has become known as the Coastline Paradox, since it suggests that the length of a coastline theoretically is infinite, or undefinable.

These theoretical notions do not even consider the dynamic nature of planet Earth. The geography of coastlines constantly changes, and sometimes quite significantly within a short period of time. In addition, the large differences in tidal influences add to the difficulty in getting more precise approximations, even with geospatial technologies having improved our capabilities of measuring such phenomena considerably in recent times.


Measuring the length of a coastline therefore is complex, and any induction will remain imperfect. Any statements of length need to be treated with caution as the totals vary depending on the approach used. For example, the World Factbook states the total length of coastlines in the world as 1.16 million kilometres. The World Resources Institute, meanwhile, states a total figure of 1.63 million kilometres in one of its studies.

When comparing the lengths of coastlines of different countries, it is therefore more important to use a consistent mathematical approach to measuring to get a clearer picture of how countries and continents compare globally. For the data used in this month’s cartogram, the estimates from the previously mentioned sources were both taken into account and combined to avoid under-representation of smaller islands but also to get a more complete picture of the varying estimates that exist.

The fact that we find it almost impossible to determine the real lengths of coasts only adds to the fascination of these areas

The cartogram shows each country of the world resized according to the total length of its coastline. It is therefore a representation of each country’s share of the world’s coastlines. In addition, the different regions are coloured in shades of blue, with the darkest shade (the Americas) representing the region with the largest share of the world’s coastlines and the lightest shade (Africa) the smallest share. Africa’s relatively small share might look surprising given its land area, but can be explained by it having a much more regular coastline that has far fewer indentations such as inlets, bays or gulfs compared to other regions. Canada, by contrast, has the most complex geography of its coastlines and is therefore the country with the longest coastline regardless of which estimations are used in our calculations.

Coasts are the locations where land meets the world’s oceans. The fact that we find it almost impossible to determine their real lengths only adds to the fascination of these areas where about 44 per cent of the world’s population live within a distance of 150 kilometres.

Benjamin Hennig (@geoviews) is Assistant Professor in Geography, University of Iceland and Honorary Research Associate in the School of Geography and the Environment, University of Oxford. He is part of the Worldmapper project and is author of www.viewsoftheworld.net

This was published in the October 2016 edition of Geographical magazine.

Related items

Geographical Week

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

Subscribe Today

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...
    Diabetes: The World at Risk
    Diabetes is often thought of as a ‘western’ problem, one linked to the developed world’s overindulgence in fatty foods and chronic lack of physi...
    The Nuclear Power Struggle
    The UK appears to be embracing nuclear, a huge U-turn on government policy from just two years ago. Yet this seems to be going against the grain globa...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...


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...


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…


An enormous hydropower development in Ethiopia is expected to put…


From nuclear warnings to whether your favourite band will ‘make…


New maps of global reptile distribution reveal significant gaps in…


Indigenous conservation schemes in Peru can be more effective than…


How are the EU member nations faring in the fight…


Violence against women violates human rights, and the lack of…