Climate change and cultural element of the French coasts

Introduction

Since the beginning of civilizations, Man has learned to inhabit the coasts and to take advantage of the resources and advantages they offer him. Local commerce, international exchanges and tourism pace the life of these very specific places and have created over time a large cultural heritage.
Today, all around the world, a large part of these marine spaces, their fauna and flora seem to be impacted by the climate changes that the world is experiencing.
France, the study area of ​​this project, is no exception to the situation. We will therefore attempt to highlight the impacts of climate change on the cultural and historical heritage of the French coasts.

Description of the study area

The good location of France in Europe

Located in Western Europe, France enjoys maritime access to the Atlantic Ocean but also to the Mediterranean Sea and the English Channel. This situation offers France the possibility of trading with the whole world very easily by sea.
This also offers the country great economic opportunity through the exploitation of the coasts and maritime spaces. Especially in terms of fishing, culture or tourism.
This exploitation has led to the appearance of specific buildings such as lighthouses to guide the many ships that find refuge there daily.

Throughout their history, the French coasts have also played a key strategic role during periods of colonization and more recently during the 1st and 2nd World Wars where many battles took place and left behind them wrecks of ships or plane
These wrecks have, over time, taken possession of the places where they landed and constitute for the most part a place of life for the local marine fauna and flora.

Lighthouse and wreck as cultural and historical heritage

These lighthouses, and these wrecks are thus part of the cultural heritage of the French coasts and participate by their presence in the marine life. Both on the surface and in depth.
However, these elements are also continuously subjected to the forces of the waters. Thus the coasts like the wrecks become fragile little by little, worn and eroded by the waves and the currents.
This is especially the case on the Atlantic coast which has much rougher waters than those that can be encountered in the Mediterranean Sea. It is also more often subject to storms which greatly increases the strength of the waves and therefore their impact on the elements mentioned.

The aim of this project will be to show whether climate change has an impact on the degradation of elements of the cultural heritage of the French coasts. Mainly by showing that these changes increase the strength and/or constitution of the waters that harbor them.

GIS uses

To achieve our goal, we will use the QGIS software which will allow us to relate the different spatial data used with the subject elements of our study, which are lighthouses and wrecks.
Data relating to specific elements of the cultural heritage of the French coasts are available on EMODnet. They allow us to locate the elements and to study the climatic changes that impact them.
Meteorological data is present on the Copernicus site and gives us a lot of information. In our case, we will be more interested in features like :

  • Water salinity
  • Water temperature
  • Current velocity
  • The size of the waves
  • The height of the sea level

We will also study certain external data such as the erosion statistics of the French coasts available on the French government website.

All this data put together will allow users of our map to follow the evolution of weather conditions. This will make it possible to act for the preservation of the elements of the coastal cultural heritage of France.

Our study area, France has a very long coastline spread along the Atlantic Ocean, the Mediterranean Sea and the English Channel. These maritime borders represent more than 65% of all the borders of metropolitan France.

PlacePopulationSurfaceMaritime spaceBorder LengthCoast Length
France 68,014,000 543,940 km² 371,096 km² 2,913 km 5,853 km
Caractéristique of France
Atlantic coast Mediterranean coast Manche coast
2,400 km1,694 km1,759 km
The three different seas

Along these coasts are the wrecks and lighthouses subject of our research.
On the EMODnet site, it is possible to have access to databases concerning lighthouses and wrecks. These data are nevertheless very numerous. For lighthouses, the database contains lighthouses from all over Europe. The wrecks are very numerous. A sorting of the data will therefore be carried out in order to keep the lighthouses of France only as well as the largest wrecks in size.

After importing the lighthouse and wreck data using a WFS link allowing QGIS to fetch the databases directly from the EMODnet site, the sorting work begins.
To do this, I started by analyzing the lighthouse databases.

The following information can be observed for each lighthouse:

  • Column 1: An identifier composed of the country identifier and a number.
  • Column 2: The country.
  • Column 3: Whether it still exists or not.
  • Column 4: Its position on the globe.
  • Column 5: Its distance from the coast.
  • Column 6: If it is located on the coast or at sea.
  • Column 7: A binary value: 1 = existing lighthouse, 0 = lighthouse no longer exists
Part of the lighthouse attribute table

Using the sort functions, it is possible to select table elements according to their attribute. I therefore selected all the lighthouses that did not belong to French territory to exclude them from the database and the map.

Data selection windows

Once that was done, I wanted to differentiate the existing lighthouses from the destroyed ones. For this I duplicated the layer and the data. On the initial layer, the destroyed lighthouses have been removed from the attribute table and therefore from the map. On the second, the existing headlights have been removed.
All that remains is to configure the symbolism:

  • Green triangle = existing headlight
  • Orange triangle = headlight destroyed

For wrecks, the operation is the same. Here I wanted to reduce the amount of data to have a readable map. The attribute table giving access to certain data such as the depth, the distance to the coast or the size of the wreck. We will use its data to select the desired elements.

Wreck attribute table

So I chose to keep wrecks over 75m located less than 25,000m from the coast. I therefore selected the wrecks that did not meet these characteristics to delete them.
The remaining wrecks will be symbolized by a double red star.

Data selection window

The result of these steps gives us a map where the lighthouses and the main wrecks of the French coasts are located. It will then be possible to compare this data with the many meteorological and environmental data available on the Copernicus site via WMS links.

Wreck Existing Lighthouse Destroyed lighthouse
22367879
Amount of cultural element

The French coasts therefore have on average 1 lighthouse every 8.6 km

The Manche coasts
The Atlantic coasts
The Atlantic coasts
The Mediterranean coasts

Analyse

To begin the research, it was necessary to find which actions could represent the greatest dangers for the wrecks and the lighthouses present off the French coast.
From this reflection came two main elements:

  • The height of the water level.
  • Erosion.

It is very easy to link the rise in mean sea level to climate change. Indeed, the rise in global temperatures is causing the melting of the sea ice as well as many glaciers all over the globe. This increase therefore endangers certain lighthouses located at sea.

For erosion, data collected around 1940 and around 2010 shows that it increased on all the French coasts between the two periods. However, it seems more difficult to link it to global warming.

Erosion of the French coasts

The speed of the water, its density or the height of the waves are elements that can impact the rate of erosion of the coasts. However, climate change seems to increase the frequency of certain meteorological events such as storms, which leads to an acceleration of the phenomenon of coastal erosion.
But also the increase in water temperature which causes an increase in its salinity and therefore its density.

Salinity of the seas

Deep wrecks are not spared and are also subject to the onslaught of currents and waves intensified by these storms.
Beyond the cultural aspect, the degradation of these wrecks also poses an ecological problem for the fauna and flora that have taken possession of them. Indeed, the degradation of these objects releases metal residues into the water and sometimes has stocks of oil still intact which threatens to spill into the waters.

Summary

Under the blows of the climate, the cultural heritage of the French coasts resists. However, things are not going well and the conditions will be more and more difficult. Rising temperatures, rising salinity, rising water levels, increased storm frequency and wave power are the factors to watch for.
The use of GIS aims to help countries, regions, cities to preserve these vestiges of the past and these buildings of the present so that they will always be there in our future.

Link

https://www.emodnet-humanactivities.eu/download-data.php

https://myocean.marine.copernicus.eu/data?view=catalogue

http://www.geolittoral.developpement-durable.gouv.fr/premiers-enseignements-r476.html

https://usys.ethz.ch/en/news-events/news/archive/2020/09/new-study-of-ocean-salinity-finds-substantial-amplification-of-the-global-water-cycle.html

https://www.climate.gov/news-features/understanding-climate/climate-change-global-sea-level