Keywords

1 The Stepping Stones Strategy

The uncontrolled growth of cities, with the consequent settlement, infrastructural and production phenomena, has determined profound alterations to the urban ecological structure, intensely transforming semi-artificial and/or semi-natural spaces. Nature is therefore often reduced to isolated fragments that are poorly connected and strongly compromised in their ecological functionality (Paolinelli 2003).

The concept of ecological network, even if usually applied to vast territorial areas, has been proposed for the reorganization of open spaces in urban areas; moreover, currently, this concept has further evolved as the ecological network has been incorporated into the “green infrastructure” model in which the supply of ecosystem services, understood as the set of direct and indirect benefits that man derives from ecosystems (Millennium Ecosystem Assessment 2005), is the main aim to be pursued.

In this perspective, traditional ecological networks evolve into polyvalent ecological networks. The polyvalency of the networks is expressed in their ability to provide ecosystem services both to biodiversity, but also to the various human activities in the area: agriculture, settlements, water use and transport (Malcevschi 2010).

However, the reticular approach requires that particular attention be paid both to the ecological/environmental quality of the network nodes and to maintaining the connections between these nodes. The issue of connectivity in cities is however extremely complex, as the continuity of connections, necessary to guarantee the reticularity of spaces, is often inhibited by urban density. The idea proposed in this work is therefore to replace “structural continuity” with “functional continuity” according to the “stepping stones” approach, borrowed from landscape ecology.

Structural connectivity concerns landscape structures regardless of any biological or behavioral attribute of the organisms that interact with them; therefore, it focuses on spatial and physical characteristics, such as shape, size and continuity of the connections. Conversely, functional connectivity includes species specific aspects and their interaction with landscape structures (Pe’er et al. 2014). Therefore, functional connectivity refers to the set of processes that take place and that binds the structural components of the connections to each other through energy flows and material transfers.

The stepping stones are structures formalized by the Pan-European Ecological Network (COE (Council of Europe), UNEP, ECNC 1996) which proposes a scheme of ecological network units formed by core areas, buffer zones, restoration areas which are areas of value or potential naturalistic value, ecological corridors, stepping stones that perform, albeit in different ways, connection functions.

The ecological corridors are in fact continuous physical connections that perform various vital ecological functions and ensure the self-regulating capacity of ecosystems, allowing key species to move between the mosaics of the ecosystem. The stepping stones, on the other hand, are fragments of habitats widespread in a territory and not directly connected, which represent important elements of the landscape for the stopping of species in transit or to accommodate specific micro-environments in critical habitat situations.

It is clear that in urban areas, physical connections are difficult to achieve due to urban density and territorial fragmentation. However, it is possible to appeal to a functional continuity that can be guaranteed by the stepping stones, i.e., by minor points of support between them sequentially (similarly to what the stones do along a ford line of a watercourse) able to perform a function of connection.

But what are the elements to connect in a city? The definition of an environmental system of connected green spaces, obviously includes not only large parks and equipped green areas, but also small gardens, squares, entire non-built areas or other open spaces (not green) such as pedestrian areas, parking lots and roads, the latter are particularly important in the urban matrix as connecting elements par excellence (Pagano 2006).

In addition to the types of open spaces, following recent studies that have highlighted their ecological importance, green building systems represent real competing infrastructures to strengthen the resilience of the urban environment. These “green” elements on buildings can in fact assume the function of “stepping stones” for fauna, in particular for some species at risk, integrating the natural elements existing around them and enriching the network of green corridors that may exist (Andri and Sauli 2012).

It should be noted that in relation to green building systems, the term biodiversity is often associated. In general, we mean the environmental value that a certain intervention can acquire from a naturalistic point of view. To achieve these objectives of increasing the environmental value, knowledge of ecological aspects and respect for the floristic coherence of the plant species to be used are fundamental requirements. By following these criteria, these works can determine an increase not only in the perceptual value, but also in the ecological and environmental value of the places. In fact, if correctly designed and implemented, they are able to activate processes “in favor of biodiversity”, starting the formation of contexts capable of favoring many spontaneous animal and plant species (Andri and Sauli 2012).

2 Intercepting and Systemizing “Support” Spaces

The phenomena of urban densification accompanied by the expansion of the built environment have led to a sharp decrease in open spaces and, in general, in spaces dedicated to collective activities and pedestrians. The parallel loss of social awareness and the consequent loss of values based on the concept of sharing go some way to explaining the low level of not only social but also functional and environmental quality of our cities. However, as urban planner Monique Keller (Mühlberger de Preux 2017) explains, recalling the characteristics of medieval cities, “a densified city is not necessarily less green, noisier and more polluted than a traditional one” but requires a change of vision in which an attempt is made to recreate a human density that favors collective life.

When David Owen, in his book Green Metropolis (2009), states that “the key to New York’s relative environmental efficiency is its extreme compactness”, he meant to underline this peculiarity, which is then closely linked to the concept of proximity.

In fact, using the words of the economist and environmentalist Charles Komanoff, Owen observes how New Yorkers have given up the “supposed convenience” of the car in favor of the “real convenience of proximity” (Owen 2010).

As shown also by recent experiences in Europe, strongly focused on densifying the full by enhancing the void, there is a need to increase the technological-environmental dimension of these spaces and, in general, of the connective tissue, so that density constitutes an opportunity to create urban environments on a human scale and proximity ones. From a methodological-planning point of view, it means working on approaches and actions aimed at “reducing CO2 emissions, combating the impacts of climate change, reducing the phenomena of environmental degradation and pollution, and improving conditions of well-being and quality of life” (Losasso 2017). The network of urban open spaces constitutes, with respect to energy-environmental issues in urban design, a strategic system of regulation and control that especially in a dense environment can more easily creep in and create the necessary conditions both for functional and environmental improvement and for mending the built environment.

In order to ensure that urban open spaces function as a real infrastructure at the service of the city, it is necessary to work on an approach that aims to reconnect the spatial and environmental fragmentation that usually characterizes dense urban environments, proposing alternatives that can be traced back to the concept of “functional continuity” described above. In fact, the ecological-environmental continuity, the comfort and safety of paths for all users qualify the urban open space network as a real ecosystem in which green and gray spaces integrate to respond to current environmental challenges: from the reduction of heat island phenomena thanks to the appropriate use of materials and the correct balance of absorbing and reflecting surfaces, to the improvement of stormwater management through sustainable drainage systems (Pregill 2020).

A dense environment is, however, usually characterized by the lack of spaces, in particular green ones, that suggests working according to new logics that, starting from the optimization of existing spaces able to provide ecosystem services, experiment especially the “micro” and “interconnected” formula. The system of open spaces will have to be organized according to a logic that integrates broader actions aimed at creating an infrastructure on an urban scale whose key elements are the relationships between the various nodes, with more punctual and site-specific actions, implemented according to the logic of urban acupuncture (Lerner 2014) and strongly dependent on the context. An infrastructure conceived in this way will be able to infiltrate the urban fabric and, where necessary, fill in gaps, helping to create the fundamental conditions for initiating both processes of conservation of existing natural resources and the interception of a series of intermediate spaces, also integrated with the built environment, which are functional connections between existing and potential spaces.

In this scenario, interstitial spaces play a strategic role, often lacking their own identity, which could instead acquire an important role in achieving what we have called the “stepping stone” approach: reserve spaces to traditional spaces that can constitute intermediate passages (even temporary and dynamic), a sort of “support” to increase the useful surface but above all to enhance or accommodate new ecosystem functions.

Moreover, national and international experience in various urban regeneration projects aimed at reconnecting buildings, people and the city in general with nature has shown how it is possible to increase biodiversity and continuity of use and the environment by working on the street system, roofs and building façades, and all those interstitial micro-spaces (including semi-private ones). It is a question of tracing trajectories that are not always coplanar, often starting from the re-naturalization of buildings and then arriving at the open space, crossing courtyards and narrow alleys that are not always completely transformable but on which it is possible to intervene in a specific way: de-paving or increasing the green component, sometimes introducing functional elements for collective activities, always taking into account the overall technological-environmental balance on the one hand and the innovation and naturalness of the proposed intervention on the other.

3 The “Mesosystem” Concept for Urban Regeneration

Following the considerations developed in the previous paragraphs, it is evident that it is of fundamental importance that the rebalancing interventions of highly anthropized areas must be structured in such a way that the territory is conceived as an organism endowed with dynamic equilibrium even if achieved through the technological control of complex functions.

The achievement of this goal is very ambitious because human activity, with the complex interrelated structures and relationships determines a significant trace in the environment that is a sign of degradation left as a burden to future generations. In order to limit this footprint, it is necessary to make as much as possible sustainable transformations from the environment in which they are located and direct the activity of rebalancing so that the footprint is contained as much as possible, and this is achieved by increasing the load capacity of the territory defined as the ability to absorb and control the phenomena of anthropization with a sustainable impact on the ecosystem.

Entering into the evaluation of the interrelationships between anthropogenic and natural phenomena with the aim of providing tools and methods for rebalancing can be helpful to look at the territory as a real ecosystem (Adler and Tanner 2013; Aitkenhead-Peterson and Volder 2010).

Starting from the premise that the natural ecosystem has a perfect functioning, the same does not happen for the urban ecosystem which is artificial, very complex and also in continuous transformation depending on many factors.

The urban ecosystem consists of artificial, semi-artificial and semi-natural biotopes and between the physical and biological components develop very complex relationships. It is, therefore, a transitory ecosystem because the anthropogenic activity does not allow it to be completely autonomous and to achieve a condition of stability.

In order to structure interventions of rebalancing, it can be effective to think about strategies based on the interconnection between microsystems. Structuring the urban ecosystem as a set of microsystems, both artificial and natural, that join together to form a mesosystem, we can aspire to establish an intermediate situation of stability. This can allow the urban ecosystem to achieve a certain “balance” by exchanging interactions with other ecosystems.

The context of Sarno is particularly significant for the purposes. This is achieved by reasoning about the transposition to the urban environment of the theory of ecological systems, also known as “development in a context” or theory of “human ecology”, developed by Bronfenbrenner to understand the dynamic interrelationships between various personal and environmental factors that affect human development (Bronfenbrenner 1981). The transposition is to consider the mesosystem as an interconnection between microsystems even at the level of development of the urban environment.

In order to provide a practical application of the previously stated concepts, we examine the case study of the regeneration of a highly anthropized area in the Municipality of Sarno in the Campania Region of Italy. In particular, the area under study extends for about 3 km in a north-west direction, including in part the densely urbanized urban center and partially the rural area almost completely cultivated.

The context of Sarno is particularly significant for the purposes of this study due to the mass urbanization, which is characterized by natural spaces that have been damaged by anthropization (e.g., the Sarno river which has a poor water quality and whose banks are cemented in many places and often without vegetation) and intersected by a complex network of infrastructures (e.g.: roads, motorways, railways, bridges, water treatment plants, distribution systems for electricity) that have contributed to altering the natural landscape, fragmenting the territory as well as changing the eco-systemic quality of the context as a whole. Subsequently, the study has focused on identifying eco-oriented redevelopment strategies for the territory under study characterized by a dense urban matrix, with particular attention being given to the eco-systemic analysis and environmental improvement interventions for the restoration of the connection elements that can allow for physical and functional continuity between the urban and surrounding rural systems.

The proposed regeneration intervention concerns the creation of natural microsystems through the use of green resources to be integrated with pre-existing artificial ones articulated on different scales of intervention. In general, the proposed interventions are replicable in order to be implemented and to activate over time other natural microsystems that can allow as much as possible the achievement of a condition of ecosystemic “equilibrium”.

Regarding the replicability of interventions on existing buildings for vertical ones it is necessary that the wall is blind or partially blind, for horizontal ones that the roofs are flat and accessible with a stairwell that allows direct access to the roof in order to make them usable not only to the inhabitants of the building but also by other citizens (Fig. 57.1).

Fig. 57.1
A site plan and illustrations. At the top there is a site plan of Sarno. A line passes through the plan and connects the vertical farm intervention. At the bottom there are 20 illustrations of different types of buildings.

Regeneration proposal for Sarno urban area: building cataloging (credits: M. L. Genito, S. Gravina)

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At the territorial scale, the proposed interventions concern the redevelopment of some degraded urban spaces and their connection through a green way (Fig. 57.2).

Fig. 57.2
A site plan of Sarno urban area. A line marks a path from the left to the right side of the map. The map has multiple labels.

Regeneration proposal for Sarno urban area: green way and open spaces (credits: M. L. Genito, S. Gravina)

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To achieve these objectives, the proposed interventions use the green component also integrating systems of energy self-production and control of rainwater management both at the scale of the building and territorial. All this in order to operate in a perspective of zero land consumption and to prepare the territory to an ever-better adaptation to climate change.

4 Conclusions

This paper, sharing the idea that density constitutes both a problem and an opportunity to creating open spaces on a human scale, suggests a strategy based on the replace of the “structural continuity” with a “functional continuity” according to an approach borrowed from the ecology of the landscape.

From an operational point of view, an important contribution to the presented approach may derive from the integrated use of digital data visualization and management tools, as well as forecasting models and monitoring systems, which are strategic both in the initial environmental status identification phase and in the subsequent evolutionary phases of the project.

All this in synergy with recent policies in the European sphere to respond to the current challenge centered on the relationship between digital technological innovation and environmental protection, consider environmental quality as a competitiveness factor.

The presented case study highlights how the objective to be achieved is to configure the territory as a fabric in which there is no boundary between the artificial and natural environment and in which each process is controlled so that its impact and consequently the irreversible degradation induced is as minimal as possible in relation to the constraints of the process itself.