2017 Advent Calendar / Advent calendar

Door 10 – It looks like reindeer…

This post is an extract from an article by Marion Ferrat, which originally appeared on Four Degrees, part of the EGU blogs network.

 

In our third look at links between geology and Christmas, Marion Ferrat looks at the ecological impact of reindeer…


When they are not driving Santa’s sleigh on Christmas night, reindeers live in different regions of northern Eurasia, including Scandinavia.

Over the past few decades, reindeer activities and reindeer farming in specific areas have had important ecological impacts. Reindeer graze and trample the vegetation covering the ground and the release of faeces and urine provides specific nutrients to the soil. This has damaged the lichen and moss-rich vegetation originally present, slowly replacing it with ‘lawns’ of nutrient-rich and digestible forage. The new vegetation type leads to what is called a positive feedback, where reindeer grazing leads to more digestible foliage, which enhances reindeer grazing, and so on. The loss of lichens also enhances the growth of coniferous trees.

Reindeer herding in Sweden – Source: Mats Andersson, Wikimedia Commons.

These on-going disturbances have ultimately created a new stable ecological state in regions of reindeer herding. But they also have consequences for local climate, through changes in the surface properties of the land.

When radiation from the Sun reaches the surface of the Earth, it can be both absorbed by the land or reflected back to the atmosphere – generally a mixture of the two. The proportion of energy absorbed versus reflected depends on the properties of the ground, including its colour. This is what is called albedo. Ice, for example, reflects a majority of solar energy and has a high albedo. Darker surfaces such as oceans absorb more energy and have a low albedo. The more energy is absorbed, the warmer that particular region (although water and land will warm up differently).

High-resolution satellite image of the border zone shared by Norway (northern half) and Finland (southern half), June 2001. A reindeer fence mirrors the border between the two countries. The difference in whiteness is due to more lichen coverage in Norway, with reindeer herding in Finland causing loss of lichen cover – Source: Grid Arendal Maps and Graphics Library.

 

 

 

 

 

 

 

 

 

 

 

The loss of lichen cover in reindeer herding areas has slowly reduced the whiteness and therefore the albedo of the land surface, changing the balance of solar energy reflected and absorbed in these regions. Reindeer can therefore have both ecological and climatic consequences, and studies have only recently started to investigate the potential positive or negative impacts of these changes in northern Scandinavia.

Geoadvent challenge update!

Congrats to Laura Kronenberg and Jason Langford, who between them have got pretty much every geoadvent window correct so far – including yesterday’s, which was Stanage Edge in the Peak District. Anyone keen to wrest the mystery prize from their grasp needs to start catching up quickly! Let us know in the comments which Plate Tectonic Story is represented by today’s window to be in with a chance…

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