The old cultural-historical landscape of the Drentsche Aa was declared the 'most beautiful landscape in the Netherlands' in 2005. Using seven picket posts, Jan Bakker shows how the landscape has changed over time.
The old cultural-historical landscape of the Drentsche Aa is part of the National stream and esdorpen landscape Drentsche Aa and was declared the most beautiful landscape in the Netherlands in 2005 by the Nature and Environment Foundation, together with the Geul and Gulpdal in South Limburg. 'Cultural-historical' by no means means that nothing has changed in a landscape; the landscape is much more dynamic than it appears at first glance. The landscape vision for the Drentsche Aa from 2017 therefore bears the motto 'Preservation through development'. By this the authors mean that the landscape 'is not locked up, but that new developments contribute to the qualities'.
To give an impression of the development of the landscape in the past centuries, the appearance of a fictitious piece of landscape is shown at seven moments in time.
The bottom
The history of this piece of Drenthe's landscape begins at the end of the last ice age, 9,700 BC:the beginning of the Holocene. The landscape consisted of three units:boulder clay plateau, cover sand landscape and stream valley landscape. Scattered over the area were a few peat bogs. The firm, impenetrable boulder clay plateaus were relatively resistant to nutrient leaching. As a result, the natural forest vegetation could last longer here than on the poorer soils, even with a certain amount of human use. The natural vegetation in the cover sand landscapes was more vulnerable to leaching of nutrients and therefore more sensitive to human pressure.
Slow soil-forming processes started at the beginning of the Holocene. The landscape became overgrown and soil organisms worked humus through the topsoil. Forest soils developed on the loamy soils, where the nutrients did not wash out. On the sandy soils in the high parts of the landscape, the precipitation with the dissolved humus particles dropped from the soil and an acidic soil with leaching layers developed:the so-called podzol soil.
From the Preboreal (9,500-8,500 BC) peat developed in the stream valleys. The climate warmed up after the Ice Age, resulting in a marked rise in the water table. A second period of peat formation occurred during the Subboreal (3,500-1,500 BC), when the vegetation changed from permanent green coniferous forest to deciduous deciduous forest. Evaporation via the trees decreased and the water table rose further, partly due to the rise in sea level.
During the Atlantic (6000-3000 BC) the so-called Atlantic forest developed, which can be compared to the oak-linden-hornbeam forest that can still be seen today in the reserve of Białowieża in Poland. In the course of the Holocene the peat crept up from the deeper parts of the valleys and the so-called stream valley shoulders also slowly became overgrown. Man used the swamp in the stream valley and dug ditches and ditches. The dewatering led to volume loss due to compaction and part of the peat literally disappeared into the air as a result of oxidation.
New Stone Age (5,300 to 3,200 BC)
The Drents plateau was still largely covered with deciduous forest five thousand years ago. It was a natural landscape, meaning that the plant and animal species were native to it and the vegetation had not been influenced by humans. There were a few small clearings in the forest, mainly around settlements and funerary monuments. The boulder clay plateaus probably contained a heavily developed deciduous forest with linden, oak, hazel and elm. Less linden and elm and more birch were found on the cover sand soils. The forest here was thinner and more transparent, with patches of clearings due to grazing by big game.
The Funnel Beaker People, who are known for their dolmens, lived in this more transparent forest. They made small clearings in the forest through fires and felling. There they practiced temporary arable farming, after which the forest closed up again. The settlements were mainly located near swamps, streams and fens, a short distance from the transition from boulder clay plateau to cover sand landscape.
Late Bronze Age (1,600 to 1,200 BC)
Due to the increasing influence of man, the landscape began to change considerably. The amount of forest on the Drents plateau decreased slowly but surely, especially in the cover sand landscapes, which were more intensively inhabited. Here the forest gave way to heath. Instead of natural forest with oaks, birches and here and there a heather plant in open spaces, an open heath was created with an oak or a birch here and there. The species were still original, but the vegetation had already been heavily influenced by humans:it was a semi-natural landscape.
The felling and removal of trees also ensured the removal of nutrients. As a result, the soil also lost its natural character. Ultimately, this development led to a dichotomy in the landscape. The cover sand areas were fairly open and consisted mainly of grassy heaths with thickets and small woods. Here were also the settlements with small arable complexes, the so-called Celtic fields. The boulder clay soils were virtually uninhabited and overgrown with heavy forest. The edges of these forests became more open due to grazing. Stream valleys were still largely covered with swamp vegetation and alder swamp forests.
Middle Iron Age (500 to 250 BC)
In the last millennium before our era, deforestation accelerated and the surface of the semi-natural landscape increased due to the advancing population. The number of settlements also increased. Due to deforestation and soil degradation, the cover sand soils became less and less attractive for habitation and agriculture. Due to the increasing absence of vegetation, the influence of the wind also increased and drifts began to occur in several places. The solution to these problems was sought in the intensification of the agricultural system and in migration to other areas.
Intensive agriculture in those days meant the introduction of mixed farms, so that fields could be fertilized. Residents moved towards the richer boulder clay plateaus, where the soils were much more fertile than on the cover sands. The necessary breaks between crops, the so-called fallow periods, could therefore be shortened. The higher fertility meant that settlements had to be moved less frequently and eventually became permanent. The core of the forests on the plateaus still contained quite a few deciduous trees, but a much more open reclamation landscape developed on the edges. By clearing the forests, evaporation by the vegetation decreased and the water table rose considerably.
Full Middle Ages (1000 to 1300)
From the last centuries before our era the population had decreased, as well as the number of settlements. Livestock farming played an important role, especially cattle and to a lesser extent horses and pigs. From the ninth century, a large number of changes occurred in Drenthe that formed the beginning of the esdorp landscape. The natural landscape had disappeared. From this time on, settlements were firmly in place. The farms got bigger.
Especially in the twelfth and thirteenth centuries, extensive essen (parcelled fields) were cultivated around the villages. Almost all essen lay on the boulder clay plateaus and were extracted from forest. Around 1500, especially on the heaviest boulder clay soils, a number of cavities or stubs remained. These were forests where oak coppice had been harvested for a long time, and where the stumps kept coming out. The remaining forests were used for grazing, felling wood, collecting litter and ferns, and for so-called akering:herding pigs in the forests to fatten them with acorns. The ashes were fertilized with a mixture of animal excrement and forest litter or mown heather.
From the eleventh century, the stream valleys were reclaimed and converted into grassland. The hay harvested here was used as winter fodder for livestock. The streamlands immediately along the stream were divided into plots with the aid of ditches and alder canals. The higher uplands on the flanks of the stream valleys were still used for collective grazing with cattle on so-called communal 'marken'. Due to the relatively low grazing pressure, the area at this time probably consisted of a park landscape of heathland with thickets and groves of pedunculate oak and birch. The heath was much more grassy (heavy grassland) and more tree-rich than in the following centuries. The much-used cart tracks from that time are still recognizable in the field to this day.
Modern time (from 1450)
Around 1500 there was a strong rise of sheep herds in Drenthe. The cattle herd also expanded strongly, which made much more manure available. From the seventeenth century onwards, farmers increasingly used heather sods as a 'filler', which was mixed with manure in the deep litter shed or in the field. Between 1450 and 1650 the essen was expanded considerably. In the stream valleys, the higher pastures were now also separated from the common 'marke'. These greenlands were provided with wooded banks and canals to separate the plots. These became new, semi-natural landscape elements. The greatly increased grazing pressure caused clear-cutting in the forest and on the heathland. In the period from 1450 to 1800, almost all remaining hollows and strubben forests disappeared. The amount of grasses in the heaths decreased, because more and more nutrients were extracted from the soil.
The cart tracks from the Middle Ages can still be seen in the Drentsche Aa area.Present
In the last century of the previous millennium, the landscape has changed very much. With the introduction of barbed wire, hedgerows were no longer necessary. Thanks to fertilizer, the moors and sheep were no longer needed for the manure. The heath became 'deserted land', which was partly converted back to agricultural land and partly planted with coniferous forest for wood production. When not only the vegetation, but also the plant and animal species occurring in it are no longer original, there is a cultural landscape in which the soil and the relief have also changed significantly. Semi-natural elements have been spared as nature reserves.
Reclamations often led to flooding. Plants have largely lost their function, causing them to disappear in many places. The water management became controllable again by channeling the streams. Modernization in agriculture was made possible through land consolidation with the accompanying plot enlargement, and the removal of vegetation superfluous for agriculture. En passant many (pre-)historical relics also disappeared. Geology, soil and water management became less and less controlling for the spatial organization of the landscape.
The disappearance of the 'moving ecological infrastructure', such as streams, made the spread of many types of plants (seeds) and animals more difficult. Connections through overflowing water and itinerant herds were broken. Scattered plots were contiguous into one large plot close to the farm, which also made it impossible to spread seeds by implements. After all, in practice, mowers are also seed drills.
After the Second World War, the use of fertilizers accelerated. It was mainly about extra nitrogen because that substance was the most restrictive for plant production. The taller and denser vegetation resulting from the nitrogen application could be mowed several times in the growing season. Only fast-growing species such as perennial ryegrass can withstand this. Species that belong to nutrient-poor conditions grow slowly. They suffer from a lack of light in dense and high vegetation and do not survive the more frequent mowing machines.
Dehydration made the manure problem even bigger. When the groundwater level drops and peaty soils become drier, oxygen enters the soil. This leads to the breakdown of organic matter, releasing nitrogen. In this way, groundwater subsidence in a so-called marsh marigold hayland can lead to an unintended nitrogen supply of more than four hundred kilos per hectare per year. That's so much that there's no going back. Dehydration therefore leads to the disappearance of species, just like fertilising.