Agroforestry

Agroforestry is a collective name for land-use systems and technologies where woody perennials (trees, shrubs, palms, bamboos, etc.) are deliberately used on the same land-management units as agricultural crops and/or animals, in some form of spatial arrangement or temporal sequence. The ecological and economic sustainability of the agricultural and forestry systems of many countries, advanced and not, is strongly threatened by the increasing introduction of exotic plant pests. This article offers an examination of the main causes behind such invasions. Some important diseases induced by non-native phytopathogens are reported, the arrival of which in the last century had a disastrous impact on the environment and the economy of vast rural areas of our country. There are also reports of some formidable emerging pathogens, which are literally devastating entire territories in various parts of the planet, with serious damage to agricultural production, the landscape, the economy and local tourism. Biological invasions, as mentioned above, are natural events. However, they have increased so frequently in recent times that they are now considered real emergencies. At the root of these calamities there are two conjunctures in the past not foreseeable, and in any case not easily governable: the climate changes on a planetary scale; and the social, economic and political changes that occurred in modern society. The ongoing global warming of the planet, caused by the massive release of greenhouse gases into the atmosphere, is leading to a globalization of climate. The consequences are multiple:

1. homogenization of biomes;
2. breaking of those biogeographic barriers that in the course of evolution have allowed a separate evolution of flora and fauna (including, of course, microflora and entomofauna) on Earth;
3. loss of current biodiversity. In our latitudes the phenomenon involves an increase in average temperatures and an alteration in the regime of annual rainfall. Such variations, in addition to causing physiological stress to the plants, also significantly alter the life cycles of plant parasites. Raising the winter minimum increases its survival rate. The propagation cycles and the reproduction rate are increased respectively in frequency and intensity. This means high biomass released into the environment, therefore strong inoculum pressure, therefore greater possibility of dispersion. Therefore, it is more likely that introduced agents will settle in new areas previously unsuitable for their biological needs.

(Marsden, Cortet,2019, p.37)

The transformation of society

The transformation of society, on the other hand, with the dizzying increase in transport, trade, tourism, and therefore the general mobility of men, goods and commodities, has made the problem exponentially grow. International trade in seeds, cuttings, seedlings, timber, vegetables for consumption, etc., offers those unwanted hitchhikers who are phytopathogenic agents more and more opportunities to transfer to new territories. But all the actions of anthropic disturbance to natural systems (road construction, power lines, buildings, crop conversions, deforestation, etc.) promote biological invasions. Everything that we call perhaps improperly progress changes the structure of ecosystems, communities, populations, interactions between species, induces the release of resources, alters the substrates and the physical environment. Forests, urban and per urban green, cultivated green, and that heap of natural and anthropic elements that form the so-called hybrid landscape in which elements of the countryside (woods, hedges, fields, ditches, rows, etc.) merge with urban and productive settlements, and with the results of the transformations of a historical and social nature (abandonment of the countryside, intensification of agricultural systems, urbanization, etc.), they bear the obvious signs. The changes to the rural environment by exotic parasites are repeated, on the other hand, since biblical times, sometimes accompanied by economic crises, hunger, famine, mass emigration. It suffices to recall the devastation of the wheat fields, in the classical era, by the agent of rust or, in more recent times, starting from 1870, the destruction of the coffee plantations by rust hemileia vastatrix. (Rosati, Burgess, 2018, p.806)

The ecological,economic and landscape damage

In our country the ecological, economic and landscape damage derived to the agroforestry environment by the accidental introduction of exotic pests is well legible on the territory. The arrival, around the twenties of the last century, of the agent of the graphitosis of the Elm has led almost to the disappearance of this species from cities and countryside. A tree, symbol of rural areas, once abundant in hedges, in rows, at the edges of the streets, in crossroads, in squares, solitary guardian of churches and monuments, has been in the space of about a century reduced by the bush disease. In fact, it is now rarely present in adult specimens, whilst it is more frequently found in bushy form as it shows, in juvenile phase, a though ephemeral resistance to the graphiosis. Some decades later, around 1940, the Chestnut cancer agent cryphonectria parasitica appeared in epidemic form in our chestnut groves, devastating cedars and fruit plants. The spread of cancer modified the vegetation belt of the castanetum favoring other species (for example, the turkey oak), therefore altering in part the hilly landscape. Among other things, he brought to its knees a thriving chestnut-growing, then important source of food, as well as economic, for the rural populations of many disadvantaged areas. The methods of analysis and monitoring of the spatial structure of the agroforestry landscape are now numerous and consolidated; however, only recently the results of these studies have begun to support and guide spatial planning policies for the formulation of spatial development strategies differentiated in relation to the needs of habitat conservation and biodiversity and landscape conservation calibrated according to the specificities of individual territories. In particular, the theme of ecological networks has become a specific object of planning within the wide area tools. (Mercer, 2004, p.316)

References

• Marsden C., Cortet J., (2019), How agroforestry systems influence soil fauna and their functions
• Mercer D., (2004), Adoption of agroforestry innovations in the tropics
• Rosati A., Burgess P., (2018), Advances in European agroforestry

Author: Chiara Di Miscio