53 Europe: Physical Geography I – Predominance of Coastline

Europe has the most amazing amount of coastline in the world.

So, what creates coastline?  For one thing, islands do.  By definition, islands are surrounded by water and thus 100% of an island’s border is coastline.

According to the Telegraph, there are many thousands of islands in Europe, including:

British Isles – 6806 islands

Norway – more than fifty thousand islands

Finland – almost 180 thousand islands

Sweden – over 267 thousand islands¹

How large are these islands?  Wikipedia lists about 500 islands in Europe of at least 50 square kilometers in area. This is quite a difference in total numbers of islands in Europe.  Apparently, very many European islands are quite small.

How big does a bit of land surrounded by water have to be in order to count as an island?  This is an intriguing geographic question.  Sometimes, Bishop Rock of the British Isles is considered the world’s smallest island, because it has a lighthouse.  The rock is less than 750 square meters in area.  Its perimeter is approximately 125 meters.  Clearly, this rock with a lighthouse adds only a smidgen of area and of coastline to Europe’s totals.²

According to Eurostat, an island should meet these criteria³:

• have an area of at least one sq. km.;
• be at least one kilometre from the continent;
• have a permanent resident population of at least 50 people;
• have no permanent link with the continent;
• not house an EU capital.

When considering the islands of Europe, Eurostat also did not include far distant colonial islands, such as French Polynesia.  Doing the count in 2003, thus including the United Kingdom, Eurostat numbered 286 island territories in the European Union.

So, it is complicated, but by whatever means of counting, Europe does have a lot of islands, including some very prominent islands like Great Britain.

What else creates coastline?  Peninsulas. A peninsula is a piece of land the juts out into a body of water, so that the peninsula is mostly surrounded by that water, except for its connection to a large landmass.  A peninsula can be a variety of irregular shapes, but could be approximated by a rectangle where one short side connects with the mainland.

In fact, let’s do some geometry.  The geometric shape that produces the least amount of coastline for a given area is the circle.  Ironically, this means that many islands, being roughly circular, do not efficiently produce coastline length given their area, while automatically having coastline given their identities as islands.

If a rectangle is used to approximate a peninsula, what shape of the rectangle yields the largest or smallest coastline?  Comparing a square to a rectangle of the same area, the rectangle always will have more perimeter or in our perspective, geographically more coastline.  Look at quora.com for an interesting mathematical explanation of this.⁴  Can you see this in the shapes above?  Shown here, the square and the rectangle have the same area.  The perimeter of the square equals the sum of the lengths of the two widths of the rectangle.  Given that the rectangle also has the measure of its height on both sides, the rectangle has a longer perimeter.

In fact, if maintaining the same area, then the longer the length and the shorter the width of the rectangle, the great its perimeter will become.  As the length of the rectangle approaches infinity and the corresponding width of the rectangle approaches zero, the perimeter is maximized. Thus, for a peninsula to maximize its coastline, it should maximize length and minimize width especially the width that connects to the mainland.

Europe has numerous peninsulas.  Some of these are very large.  The Iberian Peninsula encompasses Spain and Portugal.  Most of Italy is a peninsula.  Norway and Sweden combine as a peninsula.  Denmark is a smaller mix of peninsula and islands.  The Balkan peninsula includes continental Greece and a bit of neighboring lands.  More modest in area, but noteworthy peninsulas include Brittany in France, North Holland in the Netherlands, and the Courland Peninsula of Latvia.

Trace your finger around the borders of European countries and you will outline numerous islands and peninsulas.  So, how well does Europe stack up globally on the coastline measure. It turns out that Europe is #1 on this measure.  How so? Well, it seems that the logical way of measuring the magnitude of coastline is to compare coastline to area. Remember that circles provide the lowest coastline to area ratio and that among rectangles, squares similarly have the lowest coastline to area ratio.  This ought to be intuitive as well, for we can visually note that compact shapes like circles and squares favor area over coastline.

So, our measure for ranking by coastline is the ratio of miles to square miles (or kilometers to square kilometers) of area – miles:square miles (or km:km²).  Probably the easiest numbers to examine are expressed as meters of coastline per square kilometer of area – m:km². Using tabular data from Wikipedia⁵, I have compiled and calculated these ratios. It turns out that Europe is #1 among world regions in this measure, as shown in the table below.  By the way, Southeast Asia, ranked #2, also is replete with islands and peninsulas.

Coastline in meters per square meter

Not counting countries that are only made up of islands, Denmark is the country with the highest coastline:area ratio at 172 m:km², while Norway (including the islands of Svalbard) is second at 167 m:km²and Croatia is third at 112 m:km².

What are the consequences of having so much coastline?  Undoubtedly, there are many benefits and some costs, but certainly there are at least advantages to trade and transportation (many ports), fishing (access to the sea), exploration (Europe led the world), and tourism (beaches and scenic views).  People seeks these advantages.  Not surprisingly, in 2017 the United Nations reported that 40% of the world’s population lived within 100 km of ocean coastline.

Cited and additional bibliography:

¹ Smith, Oliver. 2018. “The Countries with the Most Islands (and the Idyllic Ones You Must Visit).” The Telegraph. August 5, 2018. https://www.telegraph.co.uk/travel/lists/countries-with-the-most-islands/.

² Patowary, Kaushik. 2013. “Bishop Rock: The Smallest Island in the World.” Amusing Planet. 2013. https://www.amusingplanet.com/2013/07/bishop-rock-smallest-island-in-world.html.

³ “Analysis of the Island Regions and Outermost Regions of the European Union: Part I The Island Regions and Territories.” n.d. Planistat Europe. Accessed March 2003.

⁴ “If the Area of a Rectangle and Square Are Equal, Then Which Will Have a Greater Perimeter? – Quora.” 2018. Www.Quora.Com. May 24, 2018. https://www.quora.com/If-the-area-of-a-rectangle-and-square-are-equal-then-which-will-have-a-greater-perimeter.

⁵ Wikipedia Contributors. 2019. “List of Countries by Length of Coastline.” Wikipedia. Wikimedia Foundation. October 15, 2019. https://en.wikipedia.org/wiki/List_of_countries_by_length_of_coastline.