Spontaneous afforestation of fallows in Italy

Pietro Piussi

(short version of D. Pettenella and P. Piussi: Spontaneous afforestation of fallows in Italy, in print)

Introduction

The most relevant change in land use which has taken place in Italy during the last 50 years, from a quantitative point of view, is not the urbanization process, as is it usually assumed, but the increase of forest area in place of agricultural land. Forest area expansion is the result of planned afforestation carried out by man but, even more, by spontaneous afforestation of fallows.

Abandonment of agricultural cultivation and spontaneous afforestation started already during the 19th century, even on small areas, and were interrupted by a resumption of cultivation during wars or other critical periods. Archaeological remnants, ancient maps and forest soil profiles frequently testify a different distribution of forest cover and tilled land in the past. Statistical data cannot provide satisfactory information, whereas the analysis of some forest stands and soils can explain the origin of some woods (Guidi et al. 1994). Not only did secondary succession involve tilled land, meadows, and pastures, but also some land already occupied by tree stands with sparse cover: chestnut groves, cork oak stands, alpine meadows interspersed with larches.

1. The dimension of forest area expansion

Italian forest land area is gradually and continuously increasing . According to the National Statistical Bureau during the last 50 years forest area increased by 14.9% (i.e. from 5.4 to 6.8 M ha), and only during the last 10 years the increment was of 7.0%.

As in many other European countries, in Italy the overall woodland area has gradually increased as a result of two different causes: the afforestation programs and the natural expansion of forest vegetation on abandoned agricultural land, mainly in mountain and hilly areas.

1.1 Afforestation programs carried out in the last fifty years

In the post-war years afforestation programs targeted two social objectives: maintenance of employment opportunities in depressed mountain areas, and prevention of soil erosion (Pettenella 1993). In the '70s afforestation policies were given a new stimulus with the promulgation of new financing mechanisms connected with the Special Development Policy for Southern Italy and the EC policy for rural areas (Romano 1986).

Act 125/1975 implemented the Special Program No. 24 in the so-called "Mezzogiorno" (Southern Italy and the islands) "to increase timber production, particularly by means of planting fast growing trees on land which is not suitably used".

1.2 Natural afforestation of marginal agricultural land

Italian forest land area increased much more as a result of secondary succession on fallows, that is as an indirect consequence of general economic development choices than of explicit afforestation programs. It is useful to remember that 54% of our country is mountainous (above 700 m a.s.l. in the Alpine area, 600 m in the Apennines) and that since the first years after Italian unification (1861) it was clear that mountain territories represented a national problem of economic and social development (Gaspari 1992), as well as of geological stability and hydraulic regime. Nevertheless, between 1861 and 1890 approximately 2 M ha of forest land have been deforested (Sereni 1977). The large majority of the 18 M Italians who migrated abroad during the last 140 years (that is since the unification of the country) was formed by farmers of mountain territories. Besides, the so called "industrial boom" which took place during the ‘50s in northern Italy in the area included between Genoa, Milan, and Turin, and later spread over large areas of the Po valley was based on a strong internal migration. The Common Agricultural Policy and the globalization of international agricultural markets contributed to the dichotomous development of the Italian economy, in which many marginal areas of the mountain territories have been more and more abandoned or extensively utilized, except where they have been favored by a tourist economy development or by the production of some typical agricultural goods required by the market.

Therefore it is not surprising that the CORINE Land Cover survey for Italy, which is part of the EU project CORINE (Coordination of Information on the Environment), in 1996 estimated a forest area of 7,2 M ha (that is 0,4 M ha more than those declared by the Italian Statistical Bureau), and another 2.5 M ha of different types of shrubland, totaling 9,7 M ha (Table 2). CORINE is based on satellite images interpretation, whereas ISTAT updates periodically data collected on the ground. A precise comparison is not possible but CORINE inventory ascribes to forest land areas which ISTAT would not consider forest. More specifically the area classified as "evolving woody vegetation, both young forests on former non-forest land, and degraded stands" amounts to 1.6 M ha.

It is extremely hard to monitor these trends since the dynamics of forest cover is very active: every year new fallow land turns spontaneously to woodland, but also forest stands evolve toward pastures with scattered trees or other land cover types as a consequence of fires or excessive grazing. Sometimes young woodlots formed on tilled land are brought back again to agricultural land use, especially in hilly regions of northern and central Italy where vineyard cultivation has become very profitable in the last years. Recently, in the territory of Chianti (Tuscany), land tillage of abandoned land already wooded started again as a consequence of EU regulations offering financial support proportional to agricultural land actively farmed (Degli Antoni 1999). Farmers, therefore, increase their farmland by tilling abandoned and low productive land. In these cases heavy machinery is used and no attention is paid to water management works (ditches, terraces, drainages etc.) previously built so that these infrastructures are damaged or destroyed and soil erosion is enhanced. This process takes place also in other regions (Accademia Nazionale di Agricoltura 1983).

As already mentioned, these afforestation processes do occur in most European countries (Mather 1992); the northern rim of the Mediterranean represents a border to it. Apparently nowhere do they reach the magnitude, both in absolute and relative values, they attain in Italy. On the southern rim of the Mediterranean, forest cover decreases and desertification prevails. In some Italian regions, nevertheless, contrasting dynamics coexist—that is expansion and reduction of the forest area— as in other southern European regions like parts of Spain and Crete (Di Pasquale and Mazzoleni 1999).

2. The successional process

Successional processes in abandoned farmland are very diversified and complex, and Italy represents an interesting field for research but also an ecological puzzle. Physical and historical factors are quite diversified and site specific. We will outline here some common features.

Reforestation depends upon some basic factors: availability of propagules (seeds or root suckers), characteristics of dissemination (mechanisms, distance from parent tree), predation of seed before or after dissemination, germination and emergence, soil conditions, inhibitory effects of various litters, competition between tree seedlings and herbaceous vegetation, predation or pathogeny of seedlings or mechanical obstacles to their emergence. Human activity is strongly instrumental in manipulating and influencing these factors, starting from the way land exploitation is interrupted. Land abandonment can take place suddenly over large areas, but generally human pressure is gradually reduced through time: fields are transformed into meadows, the number of animals grazing in mountain pastures decreases step by step, and shepherds do not eradicate the trees seedlings and shrubs, previously considered as weeds, which colonize grazing land.

Former land use is relevant in several ways. Previous crops influence the nutrient content and physical properties of the soil, as well as the type of herbaceous vegetation covering the ground and competing with tree seedlings. In formerly tilled soils stones have been usually removed, bulk density is higher and C:N is lower than in forest soils. Often the soil has been profoundly modified by terracing: species composition and growth are influenced and can be quite different in different parts of the terrace (Ghidotti and Piussi 1999).

Trees scattered on meadows or forming hedges between fields, planted in the past and utilized for wood, fodder, fruits or soil fertility improvement, have become important seed sources (Guidi and Piussi 1993 a), act as perching sites for birds disseminating fleshy fruit seeds, modify local microclimatic and soil conditions, and influence seed germination and growth through litter fall.

Often trees establish themselves immediately after cessation of agricultural exploitation or concomitantly to the decrease of grazing pressure, but sometimes shrubs, ferns and brambles occupy the ground; vegetative reproduction systems (Nocentini and Mori 1991), low palatability, thorny stems, and rapid juvenile growth grant them the resilience to withstand fires and grazing, inhibiting therefore the colonization by trees species. The pronounced adaptation to competition of bracken gives to stands of this species a remarkable longevity.

Large animals, both domestic and wild, as deer and boars which have frequently been introduced for hunting, influence the reforestation process: mechanical soil disturbance can prepare a favorable seed bed, but trampling and browsing can damage or destroy the seedlings; further growth and stand composition can be controlled by selective browsing, fraying, soil compaction, etc.

In European Mediterranean countries fire is the main threat to forest vegetation. In the past, pervasive human activities—dead wood and litter collection, ubiquitous grazing, land plowing, and the intensive exploitation of all land products—could reduce the fuel quantity and isolate woods from each other. The situation is now quite different: fuel has accumulated in woodlands and fallows are covered by remnants of herbaceous vegetation or, in the early development stages of forest succession, by biomass of young trees, shrubs and brambles in contact with the ground. This mass of flammable material propagates ground fires to crown fires and frequently links formerly separated woods. As a consequence the number of fires has increased and fire control is much harder. The origin of fires is unknown in most cases but a certain amount is caused in an attempt of the farmers to control spontaneous vegetation: a large proportion of forest fires starts in non-wooded land. Where grazing is still an important activity the use of pastoral fire further slows the process of reforestation even if hardwoods are resilient to fire injuries due to the mechanism of vegetative propagation.

3. Case studies

Some case studies may be useful to illustrate different aspects of the successional process of abandoned farmland: that one of mixed stands of Norway spruce (Picea abies), Swiss stone pine (Pinus cembra) and European larch (Larix decidua) have been analyzed in various parts of the Alps. These forests are located near the upper forest line, far below the potential forest line which has been lowered by the expansion of alpine pastures. Their dimensional and age structure, species composition and regeneration are extremely diverse on a local scale, apparently as a result of physical environmental factors as well as human action (Piussi 1994).

The timberline woods, only exceptionally utilized for local needs (fuelwood and building material for shepherds cabins), are predominantly young stands: the majority of trees originate from the second half of the past century but some individuals, which apparently survived during a period of high anthropic pressure, reach 4 or 5 centuries. The age structure reflects centuries of unabated exploitation, which culminated in the last century, and the spontaneous recolonization of derelict pastures and degraded woodlands.

The traditional practice of eradicating Swiss stone pine, which shaded the pastures, is reflected by the dominance of larch and spruce in bigger d.b.h. classes; Swiss stone pine now dominates the young generation and continues to colonize high altitude sites.

At lower altitudes in the Prealpine regions spontaneous afforestation started later, but favorable environmental conditions have caused a much faster change in the rural landscape. In this area land abandonment took place mainly starting in the late '50s and the '60s. Terraced fields and hay meadows no longer utilized were progressively invaded by various shrub and tree species; these frequently dominate the site. Ash (Fraxinus excelsior) and maple (Acer pseudoplatanus) are the dominant species on the most fertile sites, whereas hophornbeam (Ostrya carpinifolia) and manna ash (Fraxinus ornus) invade the poorest soils, usually on limestone parent material, in all Prealpine territories (Guidi et al. 1994; Fontana 1997; Aceto et al. 2000; Pelleri and Sulli in press).

Besides these dominants species, several others take part in the secondary succession: some of these are exotic, like Robinia pseudoacacia, Pinus nigra, Quercus borealis, Prunus serotina, introduced in nearby land for reforestation purposes (Folliero 1985). Robinia, used for poles and fuelwood, is precious where chestnut (Castanea sativa) has been destroyed by pathogens.

Trees scattered through the meadows have been instrumental for dissemination: these were mainly ash, used as fodder tree, and shrubs like hazel (Corylus avellana) maintained for fuelwood, poles, fodder, shoots for the manufacturing of baskets, and to build hedges. Preferred sites, and usually the firsts to be occupied, were stone walls built to separate properties or to hold terraces, supposedly because of protection from mechanical damage and lack of competition (Guidi and Piussi 1993 b).

Colonization took place gradually and lasted some years, sometimes decades. The chronological, spatial, and size structure is therefore irregular and nonuniform in different sites. After 40-50 years since the beginning of the colonization, new stands can reach 25-30 m of height (more frequently 10-20 m), and a basal area of 25-30 m² (Guidi et al. 1994).

The post-cultural succession developed also in abandoned chestnut groves, usually located on acidic soils developed on marl or sandstone parent material. The successional process has been described in several stands all over Italy, whenever farmers stop practicing traditional activities of maintenance of soil vegetation. Invasion by different coniferous (Abies alba, Pinus sylvestris) and deciduous species (oaks, alders, beech, ash, maple, black locust) has been facilitated by the decline of chestnuts attacked by Cryphonectria parasitica, Phytophthora cambivora and P. cinnamomi (Magini and Piussi 1966).The species density, as well as the areas invaded by woody vegetation, diminished at the higher elevations.

During the ‘60s and ‘70s, fires represented an obstacle to the development of succession; in fact, even if their number increased, as a consequence of the development of the road system, the higher mobility of people, and the intensive use of the country as recreation area, the individual surface, as well as the total area, have strongly decreased. The ability of hardwood to resprout easily permitted a fast regrowth so the reforestation process did not stop. New woods were establishing themselves where old trees were totally absent.

Reforestation on the Northern Apennines takes place at a slower pace. In the area of the Upper Sieve basin (Tuscany) (Torta 1999) the first species invading abandoned land are shrubs whose cover lasts some decades, whereas tree species establish a woodland cover only later. Climatic conditions typical of Mediterranean regions, especially the summer drought, seem to be responsible of this peculiar reforestation pattern, even if locally both soil conditions and human activities play a role. Presence of trees who can disseminate, wood edges, size of fallow land, wildlife activity are also important factors. Time necessary to establish a full forests cover is therefore much longer than that described for the Prealpine regions, and it seems also impossible to define a clear successional path. An analysis of landscape changes during the last 50 years in another area of the Northern Apennines developed by Vos and Stortelder (1992) shows that "fine-grained arrangements of some functionally interdependent old agricultural landscapes is being gradually broken and replaced by a coarse pattern". There is a striking and serious decrease in pattern diversity and in land unit types.

Whereas in the high Mediterranean mountains of Central and Southern Italy the reforestation process is somehow similar to that of the Alps (Fagus silvatica invades Abruzzo pastures and in Calabria Pinus nigra occupies abandoned fields), at low altitudes spontaneous reforestation following fallow takes usually much longer periods of time. In Capri island (Campania region) abandoned farmland is invaded by shrubs: Spartium junceum, Cistus incanus, Calicotome villosa, Euphorbia dendroides, Rosmarinus officinalis, Pistacia lentiscus (Mazzoleni and Ricciardi 1990).

4. Consequences of farmland abandonment

The abandonment of the agricultural land, which leads to forest expansion, reflects a deep crisis of the mountain rural society. Farmers abandoning their land are usually the youngest and most active element of the population. As the average age of rural populations rises, natality declines, and economic activities in agriculture and forestry shrink. Not infrequently, the death of old farmers and the absenteeism of many landowners prevent a precise knowledge of property borders, engendering administrative and legal problems. Thus the abandonment of the traditional land use patterns and the consequent spontaneous afforestation process have different socio-environmental and economic consequences. As it will be briefly considered in the following sections, these consequences are perceived in different ways and pose new problems to decision makers involved in forest land use planning.

Economic problems have usually been the main agents of land abandonment even if local political and social circumstance have considerably affected depopulation trends, as can be seen comparing regions with demographic recession, stagnation, or increase with political or administrative borders as can be noticed examining the population development of municipalities at the borders between Italy, Switzerland and Austria (Bätzing et al. 1996). One of the most significant component of the mountain economic development is the change of agricultural systems, with the collapse of traditional enterprises, such as farms, or communally administered systems for exploiting high altitude meadows or forests, coupled with the general trend of depopulation. Whether the new forests are welcome or unwanted, the relation between the land owners and the vegetation cover must be well known to understand if and how the new forest cover can be managed or the traditional landscape can be maintained.

Depopulation is not simply a demographic process. Small hamlets get deserted, country roads, irrigation systems, and terraces are ruined, local knowledge of natural resources and their management is lost. Demographic and social changes trigger a process of landscape transformations: functional links between parts of the mountain territory situated at different altitudes, which developed for a better exploitation of local resources (e.g. land use structures connected to animal husbandry), vanish. Consequently, cultural values vanish too.

The invasion of trees on land formerly occupied by different types of herbaceous vegetation destroys some plant associations and consequently influences the local fauna. The reforestation becomes, therefore, a threat to biodiversity. Biodiversity existing prior to reforestation, concentrated on herbaceous species and fauna depending on it (but also on hedges and tree plantations and cultivation), is mainly the result of human activities. It is hard to evaluate its importance: we know very little about the influence of selection or the introduction of crop species adapted to specific environments.

A consequence of the abandonment of cultivation in mountain territories is the maintenance of terraces which represent a common construction in the Italian rural landscape, from the coast to well above 2,000 m a.s.l. Their origin is usually unknown but presumably goes back some centuries or even millennia. Soil is present usually only on a thin layer, sometimes only 10-20 cm, whereas the main part of the terraces volume is formed by stones. Gravity, human and wildlife activities, water movements, tree roots pressure and the alterability of stony materials cause the collapse of these constructions. At the same time a woody vegetation cover may represent a protection from erosion and therefore reduce the degradation and collapse of terraces. The role of spontaneous afforestation is quite complex. Once more no model can be suggested since also the dynamic of terraces is different from place to place, according to geology, climate and times of vegetation dynamics. The consequences of these processes on the activity of mountain watersheds are still unknown.

It has been observed (Torta 1999) that woody vegetation can colonize in few decades even badly eroded sites and therefore limit the erosion process and improve the situation of degraded watersheds. Solid transportation by streams is therefore reduced and sedimentation in rivers is stabilized. This change has been favorably seen by foresters and engineers involved in watershed management, soil protection, reforestation, and land reclamation. But new problems arise along the coasts: at the mouth of rivers the reduction of solid transportation has changed the balance between erosion caused by the sea and the build-up of soil transported from eroded mountain slopes (Pranzini 1994). The consequence is the erosion of beaches, active on most of the Italian coastline, and large scale disturbances on settlements, roads and other coastal structures.

5. Public perceptions of spontaneous reforestation process

Spontaneous reforestation of mountain areas is perceived in different ways depending on the observer's point of view, on where it takes place, on the extent and type of new woodlands, and on the time frame considered (see Table 3). Reforestation can be judged as a positive or negative phenomenon, but insufficient information regarding a process still under way ads uncertainty to the evaluation.

Table 3 - Public perceptions of spontaneous reforestation process

It has been frequently discussed how changes in agricultural landscape and the diffusion of a forest cover could have influenced the rural population. Nutini (1999) developed a thorough research between inhabitants of a small town of the Apennines in Tuscany where part of the population is still employed in agriculture and animal husbandry. Young people frequently have a positive impression of the scene deriving from the abandonment of land cultivation, the degradation of abandoned buildings and the build-up of a new kind of "wild" vegetation. The new landscape represents a memory of harsh life conditions of the past and, at the same time, is an occasion for imagination and plays.

Adults who in the past were not employed in farming consider the interruption of cultivation as a negative event since it shows a lack of attention toward necessary maintenance of the land. On the contrary, those still active in agriculture see the fallow as an economical choice of a farm. Stockbreeders use fallows as a grazing ground where shrubs and young trees provide forage.

Biodiversity has also a specific aesthetic value which becomes an important issue when considering the point of view of tourism, a fundamental element of the economy in many mountain regions. The forest cover replacing the landscape mosaic created by traditional rural activities can be uniform and tedious, in many cases restricting attractive panoramic views.

From a more general point of view the expansion of forest area over large territories can be welcomed in a world where destruction of forests is a widespread process. New resources are produced and carbon dioxide is fixed. Hardwood stands formed on agricultural land abandoned 30 or 40 years ago are already exploited for fuelwood. Wood production and utilization mean jobs and an income, however small, for locals. New woods in territories formerly devoid of forest cover enrich the landscape and represent green areas appreciated for recreation.

6. Management issues in spontaneously reforested areas

"New forests" may appear where woods and forestry did not previously exist. The forest owners lack, therefore, forestry tradition and skills and have little knowledge of the most appropriate techniques (silviculture, economy, forest works and machinery) to manage these woods. Since most of the land is privately owned, and property is small and usually fragmented in different plots separated from each other, management of the new woods is not easy and some of the traditional technical solutions cannot be implemented.

But probably the most important aspect related for the implementations of some silvicultural activities is the forest owner’s entrepreneurial motivation. Type of ownership in newly afforested land becomes a key problem for future management of this land. In Italy the majority of owners can be included in the following categories:

a. Owners living far away but still interested to their land. These people are no longer farmers any more, often they live in towns or, in any case, far from their property. Their interest for the land is not based on economic grounds. They want to maintain the property rights and a sort of cultural link with their land.

b. Absentee owners. As the previous category, these people, owners of small lots of land, live in town and get their earnings from activities different from agriculture. They have no interest in managing their forest land or in selling the inherited land (frequently the transaction costs of a sales are higher than the derived revenue). No managerial services are provided to them by contractors or associations and therefore land is totally abandoned.

c. Public owners which in Italy usually are the municipalities. These were once interested in incomes provided by rights of hay mowing or grazing, substantial in relation to the total amount of their budget. Today public managers are more aware of extra economic requests of the local population, such as green areas for recreation and aesthetic values, but also job opportunities in environment maintenance activities.

It is quite obvious that both municipalities and small family farms, traditionally in charge of forest activities in mountain areas, will not have in the future the key role in the rural economy and in shaping the landscape which they had in the past. New management forms should be devised, based on contractors and external supporting agencies providing technical advise, financial support, and marketing services, with special contractual arrangements with the owners. This external support is essential: elderly people still living in the village are rarely willing to organize the exploitation of the new woods with modern criteria. Moreover, there is no management tradition for high forest, and no interest in exploitation planned in the long term. Nevertheless, where hardwoods appeared on agricultural land, small forest enterprises have been sensible to the formation of this new wood resource, and young stands are therefore utilized as coppice. Fuelwood is economically less rewarding than hardwood timber, but represents a product based on relatively short rotations and with a rather good market. In fact, some small landowners establish new woods, on very small patches of land, to utilize them as coppice. When these woods have been coppiced for the first time it became clear that the stand structure was rather irregular and thin. After coppicing many seedlings appeared between the stumps, originated by a seedling bank and newly fallen seed. The next generation will be formed by a much higher number of trees, a selection will be possible and high forest silvicultural criteria will be implemented more easily and with better results.

Positive aspects of this development are the immediate financial benefits obtained by landowners, and the possibility for local firms to develop a forest activity without sophisticated machinery and complex logging operations skill. On the negative side there is the lack of a long term planning to produce wood of better quality.

New managerial solutions must take into account the situation of the forest owners but also that of the large urban society which is, perhaps, more interested in problems concerning the management of the whole landscape than in wood production. All this represents an important challenge for foresters. It will be necessary to define spaces in which reforestation is acceptable or desirable, and others in which different types of vegetation would be preferable.

7. Conclusions

The crisis of rural societies, reflected in the spontaneous diffusion of woodlands, has its roots in economic and social events taking place mainly, or totally, outside the forest, or even the rural regions. It is one episode of social and economic change which took place in the Italian society during the second half of the 20th century as well as one of the causes of the transformation of rural landscape which is linked both to the residual rural society and to the urban society.

The same factors shape the current exploitation of all rural, but especially mountainous, regions and are mostly national rather than local. The new activities which develop are functionally linked to the urban society and its requirements: industry, production of hydroelectric energy, recreational activities, seasonal sports, transport lines (highways, railroads, power lines). Unless it becomes a tourist attraction, the old landscape shaped by an obsolete economy does not respond to the new needs, hence a different landscape develops in which a new system of settlements, roads, ski runs, and power lines alternate with young forests.

Economy and ecology must face this situation. Its analysis will show more clearly its advantages and disadvantages, in connections with the site, the type of forest cover and the section of society involved.

This analysis is badly needed: reforestation is still underway in new and extremely varied situations, therefore its potential problems or benefits will increase and change with time. Its control is theoretically possible, so that a better knowledge of the process could suggest more appropriate technical measures. In Italy the spontaneous afforestation process has been initially ignored by the scientific and technical world, and only recently have its implications on territory and society been examined (Sulli 1996; Pettenella and Piussi 1999). It seems therefore necessary to investigate the ecological and social consequences of new woods at a landscape level, including their inhabitants, and to define what use contemporary society, both rural and urban, can make of the new forests. Even if some kinds of research shall necessarily concern a restricted area, it is advisable to keep a wider picture in mind, because of the heterogeneity of landscapes shaped by mountain agriculture.

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