42 The importance of perennial for the balance of northern European agricultural landscapes

F. Herzog

The environmental, socio- n temperate agricultural land- ate Europe. It consists of fruit-trees that cultural and economic functions scapes, as well as trees and are scattered (gestreut in German) on ag- of Streuobst, hedgerows and Ishrubs outside forests are indispen- ricultural land, as also expressed in Spain riparian buffers. sable for maintaining the equilibrium by the term árboles en diseminado. The between the landscape’s productive French and the English terms près ver- and ecosystem regulation functions. gers and “fruit- meadows” basically The amount, type and arrangement of designate the same system, but are re- woody perennials on farmland depend stricted to fruit-trees on grassland. The mainly on the farmers’ decisions. But trees, however, can also be underplanted other social groups and the authorities with arable crops. This was common intervene as well, because trees have practice until the early twentieth cen- always attracted public attention. tury. Today, Streuobst most frequently In the twentieth century, trees have occurs on grassland. been increasingly removed from Euro- Typically Streuobst consists of com- pean agricultural landscapes, mainly mon fruit-trees with densities of 20 to because of agricultural mechanization, 100 trees per hectare. Rows of fruit-trees land reallocations and the increasing along streets are also considered a form specialization of farming enterprises. of Streuobst. Fruit-trees in home gar- In recent years, however, enhanced dens, on the other hand, are not, nor are awareness of the functions of trees in intensively managed orchards consist- agricultural landscapes has provoked ing of trees managed exclusively for efforts to conserve them. fruit production. In temperate Europe trees and shrubs The history of Sreuobst started in the in agricultural landscapes occur in a sixteenth century, when fruit-trees were variety of systems including wind- increasingly planted outside home gar- breaks, rows of timber-producing trees dens on open agricultural land. At that (e.g. poplar), trees that produce non- time, market production started to gain products such as nut-trees importance and fruit was increasingly on agricultural lands (both croplands processed into products that could be and grazing lands) and small blocks of stored, such as cider, must, dried fruits, natural forest retained on farmlands. fruit purée, preserved fruit in syrup and This article focuses on three of the most walnut oil, to name only a few. The mar- prominent systems: Streuobst (fruit- ket demand increased further in the nine- trees scattered on agricultural land), teenth century when the development hedgerows and riparian buffers. The ar- of railways made it possible to sell fresh ticle briefly describes the systems, sum- fruit on a larger scale in urban markets. marizes their history and discusses their Subsistence fruit production has always major environmental, socio-cultural been important as well, particularly in and economic functions. Together, times of war. In Germany, the last large- they help preserve the ecological bal- scale planting activities of Streuobst ance of the landscape, mitigating the fruit-trees took place during and after Felix Herzog prepared this article while working loss of biodiversity and the pollution the Second World War, when the market at the Centre for of ground and surface water caused by provision of fresh fruit was insufficient Environmental Research industrialized farming methods. (Weller et al., 1986). Ltd in Leipzig, Germany. He is currently at the Swiss Market forces and subsistence produc- Federal Research Station STREUOBST tion only partly explain the success of for Agroecology and Streuobst is the most prominent tradi- Streuobst. The political authorities sup- Agriculture in Zurich, Switzerland. tional system in temper- ported its development from the begin-

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ning. For example, decrees and regula- tions linked permission for citizenship or marriage to the obligation to plant a certain number of fruit-trees or mandated the installation of tree nurseries in the villages to provide planting material for farmers. In 1752, Frederick II (the Great) ordered that: “In each village, a cooperative, well-furnished tree nursery must be in- stalled and run by a man trained in the handling and nursing of trees and capa- ble of educating the villagers. In these tree nurseries, an adequate stock of fruit- trees must always be available so that, once all gardens have been planted, the planting can be extended to streets in and near the village. ... If a surplus of fruit is produced, it is to be sold to the cities” FIGURE 1 Landscape in northwestern (translated from Lucke, Silbereisen and Switzerland in the eighteenth Herzberger, 1992). Intellectuals sup- century, with fruit-trees scattered ported Streuobst as well, forming what around the village and on the hillsides (drawing by Emmanuel would be considered today non-govern- ... and at the end of the Büchel) ... mental organizations (NGOs). In the twentieth century (photo), with hillsides still devoted to early nineteenth century, priests, medi- Streuobst cal doctors, chemists and teachers gath- ered in pomological societies (pomology being the science of the growing, storing, processing and mar- keting of fruits) and collected, described and evaluated the numerous existing fruit varieties in order to promote those of particular value (Lott, 1993). Streuobst reached its height in the middle of the twentieth century, when intensive fruit production systems based on dwarf trees began to replace it. Today, most European table fruit stems from intensively managed orchards. Again, this development can be ex- plained by the interaction of market forces and government intervention. National governments and the Euro- pean Union (EU) subsidized the removal F. HERZOG of Streuobst apple, pear and peach trees because the system was no longer considered profitable. In Baden- Württemberg, Germany, for example,

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the number of Streuobst fruit-trees was often on earth banks (in northern Ger- sedimentation of water bodies from soil reduced from 24 million to 11 million many, for example) or on stone walls (in erosion on adjacent agricultural lands. between 1951 and 1990 (Statistisches calcareous hilly and mountainous re- Bundesamt Wiesbaden, 1954; Maag, gions). They serve as natural fences, ENVIRONMENTAL FUNCTIONS OF 1992). often between pastures and arable TREES IN AGRICULTURAL Today, 11 European countries have fields, and at the same time yield timber LANDSCAPES about 1 million hectares of Streuobst and non-timber tree products such as Modern, industrialized agricultural (Herzog, 1998). A belt of Streuobst fuelwood, small fruits, fodder and herbs production in Europe has boosted food stretches through northern France, for traditional medicine. security, but to a great extent it has done southern Germany and Switzerland to The earliest written documents on so at the expense of the environment. Poland (Figure 1). The share of the agri- hedgerows date from Roman times. For The main environmental problems at- cultural area planted with Streuobst is example, Caesar reported (in De Bello tributable to modern agriculture are the particularly high in hilly areas, where Gallico) that the farmers on the lower loss of biological diversity and the pol- the topography limits the potential of Rhine had established living fences lution of ground and surface waters. more intensive forms of land use. In consisting of trees and thorny shrubs Trees help mitigate these problems. northern Spain, in the French depart- which were cut and shaped in order to ments of Normandy, Lorraine and Alsace, interweave the branches and create Biodiversity in the German federal state of Baden- “walls which often provided such The potential of trees to enhance bio- Württemberg and in parts of Switzerland strong protection that it was impossi- logical diversity in agricultural areas Streuobst covers up to 5.4 percent of the ble either to walk or see through them” can be explained by the numerous agricultural surface (Herzog, 1998). Un- (translated from Speier, 1997). Hedge- physical gradients (for example, dry/ fortunately, statistics on extent of row planting was intensified in the late moist, shaded/sunny) that occur when Streuobst or other systems of trees in ag- Middle Ages, when in many places there trees and annual plants are interspersed. ricultural landscapes are not available was a shortage of wood because of A variety of ecological niches is cre- for many European countries. Similarly, overexploitation of the forests. Hedge- ated which offers a range of habitats for national statistics on trends in coverage rows provided wood and replaced plants and animals with different envi- are generally lacking. wooden fences. Their planting peaked ronmental requirements. in the eighteenth century and then The biodiversity harboured by the HEDGEROWS AND RIPARIAN started to decline. The reduction be- Streuobst system has been widely BUFFERS came particularly marked in the second noted, with emphasis on the frequency Hedgerows and riparian buffers are lin- half of the twentieth century as a result of endangered species (cf. Bünger and ear structures. Hedgerows are rows of of reallocations of agricultural hold- Kölbach, 1995). shrubs or bushes forming a hedge, some- ings to create larger field plots. Bazin Funke et al. (1986) found that, as a times with a central row of trees. They and Schmutz (1994) have estimated consequence of the abundance of eas- are often coppiced. Riparian buffers are that since 1960, 40 to 80 percent of the ily decomposing and the close small strips of forest trees located along European hedgerows have disappeared interaction of biomass producers and streams or rivers. or degenerated through lack of mainte- consumers in a small area, the overall Traditional “hedgerow landscapes” nance. In France, for example, the total biomass of arthropods in Streuobst was are seen in Europe’s coastal areas and in length of hedgerows was reduced from 2.7 to 7 times higher than in nearby for- hilly and lower mountain regions. Ex- about 1.2 to 0.6 million km between the est ecosystems. amples are the bocages in Brittany and late 1960s and 1980. The type and frequency of meadow Normandy in France, the hedgerows in Whereas hedgerows are often planted, utilization (pasture or mowing or both) southern and central England and Ire- riparian buffers are often remnants of and application of fertilizer strongly land, the Knicks and Wallhecken in former river plain forests with willows influence the plant associations found Schleswig-Holstein and Westphalia in (Salix sp.), alder (Alnus glutinosa) and at a site. The diversity of herbaceous Germany. Originally, hedgerows were a variety of hardwood trees (Fraxinus species increases with light availabil- planted in order to separate individual excelsior, Ulmus sp., Acer sp., Quercus ity and is greater if the site is mown rather agricultural fields and/or possessions, robur). Riparian forests protect against than grazed. It decreases with the inten-

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sity of the meadow’s utilization rieties in Streuobst systems creates use- exchange of individuals between (Breunig and König, 1988). ful synergies between the conservation populations, preventing isolation and Streuobst provides habitats that have of genetic material and conser- genetic degradation. An example from become scarce in European agricultural vation (Herzog and Oetmann, 1997). eastern Germany is shown in Figure 2. landscapes. The system is an important Hedgerows and riparian buffers each Even in this landscape, which is char- refuge for small mammals (including represent an ecotone, or a transitional acterized by large field plots and inten- bats), reptiles and amphibians. It re- zone between vegetation types, known sive agricultural management, hedge- ceives particular attention, however, for to harbour a rich assemblage of species rows, riparian buffers and tree rows its potential to host birds, including (Risser, 1990). Riparian strips also con- provide at least a fragmentary network numerous species whose populations tribute to fish habitats, providing shade of biotopes (regions uniform in envi- are declining or endangered. Wood- and the shelter offered by roots and ronmental conditions and plant and ani- peckers, nuthatches (e.g. Sitta euro- fallen woody matter. Hedgerows and mal populations). paea) and treecreepers (e.g. Certhia riparian buffers are a major habitat for brachydactyla, Certhia familiaris) feed birds and invertebrates. The inverte- Soil conservation and water quality on insects in the trees’ wood and bark. brates contribute to the stability of the Water pollution mainly results from soil Holes or crevices in older trees provide adjacent agro-ecosystems. In early particles (in surface water), leached nesting opportunities for birds that nest spring, hedgerows provide fodder for agrochemicals and excess fertilizers (in in caves. herbivorous insects, leading to buildup ground and surface water). Prevention Streuobst systems have a large amount of their populations, which in turn leads of erosion and leaching is thus a prior- of intraspecies as well as interspecies to rapid increases in the populations of ity. It can be achieved by adapting the variability. Fruit varieties selected by entomophagous parasites and preda- cultivation techniques and by modify- local farmers have traditionally differed tors. Later, the parasites contribute to ing the landscape structure – a com- regionally. Streuobst sites normally the control of aphids on the nearby bined approach being the best solution consist of several varieties and types of agricultural crops (Schulze and (Haycock and Muscutt, 1995). Linear trees, chosen by farmers for their differ- Gerstberger, 1994). landscape elements such as hedgerows ent pollination characteristics, differ- Hedgerows and riparian buffers are not and buffer strips are the most powerful ent times of maturity so the harvest will only valuable habitats but also corri- tools of landscape planners because be spread over time and different utili- dors for the movement of birds and they have the potential to control the zation and storage properties of the insects. They link forests, small fluxes of matter and energy in land- fruit. The preservation of fruit-tree va- and Streuobst sites, allowing for an scapes while requiring only relatively

Hedgerows Tree rows and alleys Riparian buffers Streuobst Small woods, bushes Rivers Major roads Water Grassland Forest FIGURE 2 Arable land Ecological network around Settlements two villages in the Torgau 0 1 2 km District, western Saxony, Germany, consisting of Streuobst sites, fruit-tree Source: Digital biotope map of the Saxony Agency for Environment rows, hedgerows and and Geology (SLUG), Dresden. riparian buffers

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Winter landscape in northwestern Switzerland F. HERZOG

limited surface. Investigations at the subsoil. For example, a 19-fold decrease vary according to the culture), and catchment level have shown that linear in nitrate concentration has been ob- visual aspects are often a major factor structures of perennial vegetation dis- served in groundwater passing under driving landscape change. The visual tributed across agricultural areas in den- shelterbelts in Poland (Ryszkowski, quality of most traditional agricultural sities adapted to the local conditions 1992). landscapes in temperate Europe is re- and agricultural practices contribute to Similar mechanisms are at work in lated to the harmonious contrast of an improved water quality (Mander, riparian buffers maintained between ensemble of landscape elements includ- Kuusemets and Ivask, 1995; Vought et farmland and surface waters to mitigate ing closed forest, structured arable al., 1995). negative impacts of agricultural man- fields and green meadows, interspersed Hedgerows have been planted as wind- agement. Riparian buffers prevent soil with small woods, hedgerows, etc. Fruit- breaks in regions vulnerable to wind eroded from adjacent land from wash- trees, which are often grouped around erosion, such as the loess plains of ing into rivers or streams, where it would settlements, connect them to the open France and eastern Germany and the silt up the aquatic system. A buffer zone agricultural land. As patches, rows, scat- sand dunes of the coast of northern Den- consisting of a stepped structure with a tered individuals and even single trees, mark. Windbreaks protect pasturing herbaceous strip adjacent to a strip of Streuobst can enhance the local topog- animals not only from wind, but also shrubs and bushes, followed by a forest raphy. With the differing shapes, sizes from excessive temperatures. In Den- strip next to the river or lake shore, re- and colours of blossoms, leaves and mark, planting of hedgerows was found tains nutrients (nitrogen and potassium) fruits, fruit-trees enrich the scenery’s not only to help prevent erosion, but and pesticides from polluted overland variety and diversity in space as well as also to help improve the microclimatic and subsurface water. The tree strip also time. conditions. Comparative studies sug- filters air polluted with agrochemicals Trees have always had an important gested that effectively spaced hedges and reduces the growth of aquatic plants role in myths and customs. In ancient could contribute to an average annual by shading their environment (Mander societies, trees were symbols of fertil- increase of 5 percent in the yield of ag- et al., 1997). ity and well-being. Among the fruit- ricultural crops (Bazin, 1994). trees, cherry and apple trees have par- Hedgerows and shelterbelts root SOCIO-CULTURAL FUNCTIONS ticularly often been associated with deeper than annual crops and have The landscape’s socio-cultural services myths, beliefs and customs. In many higher evapotranspiration. As a conse- are beneficial for human well-being. regions, the blossom of fruit-trees is a quence, they function as “ecological Scenic values, recreation and regional symbol of spring. Today, images of trees water pumps” (Ryszkowski, 1992) and identity are closely linked. Landscapes are often used in the marketing of prod- at the same time intercept nutrients con- are perceived as pleasant if they are ucts that are supposed to be particularly tained in lateral flows of water in the structured in certain patterns (which may environment friendly. In a political con-

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text, they symbolize the green or alter- Streuobst products are sold at a higher lishment of hedgerows and forested native movements. The particular aes- price than products from intensive riparian buffers is subsidized by agro- thetic role of trees in landscapes was agriculture. They are labelled as par- environmental programmes which are recently underlined in a cultural event ticularly environmentally friendly and based on EU regulation EEC 2078/92, in which the famous artist Christo healthy, and increasing numbers of con- on agricultural production methods wrapped 178 trees with polyester in sumers are ready to spend extra money compatible with the requirements for northern Switzerland. The “Wrapped for this kind of food. The higher prices protection of the environment and main- trees” event, linked to an arts exposi- are an incentive for farmers not only to tenance of the countryside. The imple- tion on “The magic of trees” and to the harvest the fruit, but also to maintain mentation and effect of those pro- presentation of the nature protection the Streuobst trees and with them the grammes varies strongly between activities of several NGOs, was highly entire system. member countries, however. publicized in the international press and Qiu and Prato (1998) have estimated A general, underlying problem rests attracted tens of thousands of visitors. the potential financial benefits of ripar- in the fact that the presence of trees on ian buffers in terms of cost savings rela- farmland may change the legal status ECONOMIC FUNCTIONS tive to achieving water quality objec- of the land, bringing it into the domain The reasons for the observed reduction tives by other measures. Many vital of and nature protection laws. in the number of trees in European agri- environmental and socio-cultural ben- These laws often restrict the farmers’ cultural landscapes in recent decades efits, however, cannot be monetized, options. Knowing that Streuobst or have mainly been economic. Above all, and these would have to be taken into hedgerows cannot be removed once the trees have been removed to increase account in order to judge what Barbier they are established, farmers may be the efficiency of mechanized agricul- (1990) calls the “social efficiency” of reluctant to install them or may even ture. Streuobst is not generally seen as the system. remove some of them before laws that a profitable branch of farming activi- protect them come into force. ties (Herzog, 1998). Nevertheless, ap- THE FUTURE OF TREES The future of European agricultural ples from Streuobst, for example, have IN AGRICULTURAL LANDSCAPES landscapes is closely linked to the fate a considerable impact on the European IN EUROPE of its trees. Only a “landscape approach” fruit market (Rösler, 1996). The fact that Recognition of the importance of the can lead to coherence between agricul- Streuobst is still quite popular in hilly services provided by trees has led, since tural, forest and environmental policies areas indicates that in certain environ- the 1970s, to endeavours to stop the re- (European Union DG VI, 1998). ments it has comparative advantages moval of Streuobst and hedgerows from Streuobst, hedgerows and riparian buff- over other types of land use. It integrates agricultural landscapes, to conserva- ers can contribute to mitigating the pol- well with cattle and crop production on tion of the remaining sites and even to lution of ground and surface water and medium-sized family farms, if the fruit- replanting. This movement was initi- the reduction of biological diversity. picking season is between the labour- ated by proponents of nature protection They are valuable tools for maintain- intensive planting and harvesting sea- and has induced policy changes. In Ger- ing ecological balance. In addition to sons and if family members are available many, for example, the policy of the the traditional systems discussed here, to help with the harvest. 1960s which subsidized the removal of the development of novel agroforestry In Germany, Streuobst is an example Streuobst has been reversed. Today, systems combining hardwood trees for of successful cooperation between na- Streuobst is protected in five of the 16 timber production with arable crops or ture protection and agriculture. Pursu- federal Länder, and most of them have grassland (Dupraz and Newman, 1997) ing a “protection through utilization” implemented specific programmes to will provide new approaches for the in- approach, numerous environmental support the management of Streuobst tegration of trees in farming systems in NGOs have allied themselves with farm- systems. Similar programmes exist for temperate, industrialized countries. ◆ ers and developed alternative market- hedgerows and riparian buffers (e.g. ing systems for Streuobst products. Schulze and Gerstberger, 1994). In There are about 90 initiatives that or- France, up to 1 500 km of hedgerows ganize production and marketing, are planted every year (Schmutz, 1994). mainly of must and cider (Lobitz, 1997). In most European countries, the estab-

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