A Brief History of European Forests

Berchtesgaden

The history of forests in Europe over the past 130,000 years encompasses a wide variety of changes for all parts of the continent. One location could transition from dense deciduous trees to evergreens to barren wind swept arctic tundra as the centuries passed.

We will start with the last interglacial warm period, then go through changes as a result of the last ice age, and finish with the history of European forests during our current interglacial warm period.

Forest Types Various Types of Forest
From the Left: Taiga/Boreal (Spruce, Fir, Cedar, Birch, Aspen)
Coniferous (White and Red Pine)
Deciduous (Oak, Maple, Beech)
Steppe (Barren with sparse grassland)

Previous Interglacial Warm Period (Eemian Warm Period)

Europe experienced a climate period known as the Eemian Warm Period from around 130,000 to 115,000 BC. During this time, Europe was on average about 3.5°F (2°C) warmer than present day temperatures.

Across most of Europe, it seems there were successive waves of various tree species during the Eemian, as the climate was not entirely stable during this 15,000 year period. During the early years, coniferous trees (pine) populated the land immediately following the retreat of glaciers, followed by deciduous oaks and maples as temperatures increased. Conifer forests made their way north into Scandinavia as the climate there became more hospitable and competition from other tree species pushed them out of central Europe.

Periods of Glaciation Glacial and Interglacial periods
Source: NOAA

The warmest part of this phase saw temperatures 4-4.5°F (2-2.5°C) above present day. And so the 'optimum' Eemian climate saw temperate forests extended much further north than at present, with temperate hazel and alder populations growing as far north as the Swedish Lapland, around 67° latitude at the most northern part of the country.

In the Mediterranean region, deciduous forests were replaced with other tree species such as olive and evergreen oaks. This area began to resemble that of our present day.

There is some evidence of a mid-Eemian cooling event around 120,000 BC on the basis of tree pollen in the archeological record. This cooling event may have lasted for several hundred years. More open forest-steppe vegetation seems to have appeared where there had been dense and closed forests. The cooling event likely resulted from a weakening of the Gulf Stream Atlantic current. After this, the climate never returned to its previous warmth.

Coniferous forest Coniferous Forest - Küblis, Switzerland
photo credit: Swiss National Forest Inventory

After about 115,000 BC, there was a strong replacement by spruce and then back to pine once again as the Earth drifted towards its next period of glaciation. At first, the summers were cooler while the winters became milder. Relatively frost sensitive species such as holly and ivy became more widespread across northern Europe. Conifers also became abundant during this phase.

The forests then began to thin out and the land began to clear once again as ice built up in the northern latitudes and the climate became increasingly more arid and cold. The 15,000 year long era of lush forest during the Eemian Warm Period was drawing to a close.

Last Period of Glaciation (Weichsel/Würm Glacial Stage)

A cooling event that appears to be quite rapid begins around 110,000 BC. Sea levels fall and a massive ice sheet builds up on the mountains of Scandinavia but does not yet reach the sea. Conifer forests endured in what is present day central France and Germany, with tundra forming in northern Europe.

Around 103,000 BC the climate warms slightly and forests return to southern Britain and Scandinavia. This is followed by successively sharp cooling periods where the forests of Europe are progressively pushed to the south.

Ice Age Europe Ice Age Europe
Source: Levadoux, 1956

A new period of glaciation sets in for the European continent, with temperatures on average 10–20°F (5–10°C) colder than present day. Temperatures drop to 75°F (40°C) colder than present day over ice sheets which now cover Scandinavia and Iceland, extending into the sea. Northern Britain is covered by ice year round and sea levels ultimately drop 400ft (120m) below present elevations. Land now connects Britain and Scandinavia to the European continent. But this new land is only tundra. The entire continent becomes much colder and drier.

Previously dominant beech trees are forced out of central Europe. They will not return for another 100,000 years. Forests are confined to southern Europe and the eastern foothills of the Alps. Atmospheric CO2 levels fall below 200ppm making it much more difficult for plant life to thrive.

During this glacial phase, sudden warm and moist periods occurred which often took the European climate from full glacial to conditions almost as warm as today. These are known as interstadials, and were likely caused by the Atlantic gulf stream turning on and off. Between 113,000 and 12,000 BC, there are at least 24 of these sudden warm periods. These brief warm periods during the glacial phase lasted between a few centuries to as long as 2,000 years. This was sometimes enough time for forests to push north again, at least where there were no ice sheets, before rapid cooling returned. Open woodlands of birch, pine, and other conifers colonized northern Germany and Britain. However, many of these brief warm phases that occurred during the later years of the glacial period do not show signs of a resurgence of woodland to northern Europe.

In southern Europe, forests that had started to expand north were decimated when dry glacial conditions returned. Oaks underwent a temporary resurgence in Sicily. The early interstadials may have produced a widespread mixed forest cover across southern Europe, if only for a few hundred years. The later interstadials seem to have given rise to abundant open tree cover across southern Spain, Italy, and Greece.

Polar Desert Polar Desert

The later years of the last glacial period were some of the most cold and dry. Large ice sheets were present across northern Europe, and ice covered the Alp and Pyrenees mountains. Forest and woodland were almost nonexistent anywhere on the continent except for isolated pockets close to the mountain ranges in southern Europe. Sparse grassland or polar desert covered much of Europe, with permafrost extending down to the latitude of central France. Drifting sand and wind erosion of topsoil was common. Desert animals such as antelope lived as far west as France.

Research shows that mean temperatures in central Europe were comparable with those of the northern coast of Siberia of present day.

Current Interglacial Warm Period (Holocene)

taiga boreal forest Taiga/Boreal Forest

Around 11,000 BC, the European climate begins to rapidly warm and moisten. Research on insect community fossils suggests that temperatures were at least as warm as present day for the next 500 years. Open woodland consisting of birch and various boreal conifers seems to have appeard quickly across much of European Russia. North western Europe remained lacking in trees, remaining an open tundra with some dwarf willows and juniper up to 10,000 BC, with steppe cover still dominating nearly all of Europe.

From 10,000 to 9,000 BC, the steppe vegetation of the Mediterranean areas is gradually replaced by woodlands, with various boreal species such as birch and willow prevailing in southern France and the Pyrenees foothills. Dense forest became established in some areas of southern Europe. Pine and beech forest were established in the Iberian Peninsula (Spain) by 9,500 BC. Evergreen oak begins to appear in southern Spain until around 7,500 BC when it is replaced by closed oak forest. In Greece, deciduous oaks and pines were present, but only a minor component of the landscape. A large ice sheet still covers Scandinavia and glaciers return to northern Britain.

From roughly 10,500 to 9,500 BC, the climate appears to have become more cold and dry in what is commonly referred to as the Younger Dryas. This caused the disappearance of the woodland cover over nearly all of Europe once again. Conditions might not have been so severe across north western Europe, with a mixture of patches of trees and grassland being widespread. Most of Germany and Poland become forested tundra. Coniferous woodlands survived in the southern foothills of the Alps. There is some evidence that Greece became even drier than during the previous ice age, and thus had almost no forests during this brief dry period.

Deciduous Forest Deciduous Forest

This cold and dry period ends over a period of 75 years, and temperatures become warmer than present day. This time, 8,000 BC, marks the beginning of the 'Holocene Interglacial Period.' By 6,000 BC, forests had become closed across the entire continent. Beech trees become the dominant forest type for continental Europe, southern Britain, and southern Scandinavia.

The period from 8,000 to 7,000 BC seems to mark the most heavily wooded time for the European region. Parts of southern Europe that are today dry and with few trees were closed in with deciduous forests. Iceland had open boreal forest. Northern Israel was populated with open woodland.

The timberline in the central Alps reached an elevation of around 8000ft (2500m), about 500ft (150m) higher than today's timberline elevation. This is the highest timberline elevation during the Holocene Interglacial Period.

Temperatures were about 3.5°F (2°C) warmer than present from 5,000 to 2,000 BC in what is believed to be the warmest period of the Holocene. This allowed forests to spread further north than present day, with deciduous forests establishing themselves far into Scandinavia, and conifer forests populating the northern coast. Dense forests were even able to reach the Icelandic highlands.

It should also be mentioned that there was a significant elm decline around 3,000 BC throughout Europe. It is thought that this was caused by disease and a possible weakening of the trees.

Farming

Land suitable for cultivation or pasture Land suitable for cultivation or pasture.
Source: Quaternary Science Reviews

From 5,000 to 3,000 BC, agriculture spread to most parts of Europe. But this was at a small scale and only affected forests locally. Hunter gatherer cultures cultivated the forests for their own purposes on a small scale as well. In dense woodland, it is very difficult to spot game much less to chase after it. The types of underbrush in dense forests were not a good source of food for wild animals either, with the exception of trees which dropped nuts.

So hunter gatherer cultures would burn down some forests to clear the land for grazing animals. The larger trees would generally survive forest fires and create many new saplings which attracted all sorts of grazing wildlife. This is a perfect setting for hunter gatherer tribes. This occasional burning of forests by humans may have caused an increase in the fire resistant cork oak.

Forestation of Europe Forest cover in Europe.
Source: Nature Research

Significant effects of farming on the landscape of Europe didn't begin until around 2,000 BC. Although, large areas of forest in central and northern Europe were still untouched by farming before 1,000 BC. After this time the dense forest gave way to pasture woodlands and open landscapes, kept open by the increasing number of grazing animals feeding on saplings.

By 1,000 AD, European agrarian civilization was firmly established and doing quite well. By 1,500 it had pushed far to the east, and thus forests in present day Russia were also cleared for farmland.

Around 1,000 AD, the Norse had established settlements in what was then a forested southern Greenland with a population as high as 3,000. Their communication with Norway was cut off in 1410. A ship visiting Greenland in 1585 found no trace of them. Today, the soil in this area is permanently frozen.

Europe experiences brief cooling events during this warm period, resulting in a lowering of the timberline on mountains. These cooling periods are recorded in tree rings during the 6th and 19thcenturies.

Europe's Current Forests

Current European forest cover Current European forest cover.
Source: European Environmental Agency

With a constantly changing climate, there is no perfectly stable type of forest anywhere in the world, but especially not in Europe. The land is a barren, cold, and dry arctic tundra at one point in history, and a humid, warm, and dense closed in forest at other times.

Beech trees dominate the forests of present day France, Germany, and southern Britain. Conifers are the majority in eastern Germany, Poland, and southern Sweden. Birch and Aspen dominate Britain, Norway, and northern Germany. Boreal forests are the staple of central Scandinavia and Finland, while tundra exists in the far north of Norway.

Although farming has drastically altered the landscape, large tracts of forest have been preserved in various parts of Europe. These include The Alte Buchenwalder Deutchlands, Unesco Biosphare Entlebuch in Switzerland, and The Carpathian Mountains in Northern Romania.

The European continent is still in the midst of a relatively warm and humid time that may continue for thousands more years, continuing the lives of the continent's beautiful and ancient forests that we are enjoying today.

For there is hope for a tree, if it be cut down, that it will sprout again, and that its shoots will not cease.
Job 14:7


Originally published
Researched and Written by: Thomas Acreman


Sources:
  Secrets of the Ice Age by
  Allgemeine Geographie by
  Documents pour la carte de la végétation des Alpes by
   - Sonoma State University
   - Quaternary Science Reviews
  
   - Oak Ridge National Laboratory
   - European Commission
   - NOAA
   - NOAA - PDF
   by P.C.Tzedakis, B.C.Emerson, G.M.Hewitt
   - Archived - NASA
   - NASA
   - Cambridge University Press
   - Willy Tinner and Jean-Paul Theurillat

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A Brief History of European Forests
Comments:

  • Liz
    2020-08-26
    Wild temperature swings throughout the years!
  • Wake
    2020-08-27
    Indeed! All the more reason to be thankful for the forests we are enjoying today.
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