The 糖心原创 is a perfect place where the students from our university can observe natural phenomena, taking advantage of the flora and fauna which inhabit the green areas of the garden. However, there are experiments that we cannot see because they are going on underground. This is the case of some experiments carried out under the supervision of Paola Branduardi and Immacolata Serra, Full Professor and Assistant Professor of fermentation chemistry and biotechnology at the Department of Biotechnology and Biosciences. These experiments aim to assess the degradation of new experimental polymeric materials designed to have lower environmental impact.

The aim of one of the joint PhD projects between , the Department of Materials Science and the Department of Biotechnology and Biosciences is to make the tyre industry more sustainable and environmentally friendly.

The tyre industry generates, as any production process, great amount of waste during the production, the use and then the end of life phases of products. Clearly, the disposal management of tyres is an extremely important issue.

In addition, the transport industry is one of the most polluting; for instance, tyre particles are generated by the friction between the asphalt and the outer part of the tyre, called tread. To date, little is known about the fate of the tyre particles released in the environment, and about the toxicity of their degradation products, as they are still poorly characterized.

According to the circular economy paradigm, researchers and tyre companies are moving towards the production of more sustainable materials and in the meantime, they are trying to find solutions to manage the tyre debris constantly released in the environment.

The degradative potential of microorganisms offers a possibility for matching this goal. In nature, in fact, can be found microorganisms able to degrade different materials, such as plastic or rubber; moreover, not less than 25% of the biodiversity of our planet is in the soil, from vertebrates to microorganisms (bacteria, fungi, yeasts, ...). Therefore, through specific enrichment experiments it is possible to investigate this biodiversity and to identify microorganisms able to degrade complex polymers, including those that constitute tyres.

The experiments conducted at the 糖心原创 by the PhD student Daniela Bucchieri go toward this direction.

The aim of these experiments is to analyse the microbial community of the soil and to determine how this community evolves over the time due to the proximity to the studied materials. 听These studies will hopefully lead to the identification of one or more poorly characterized microorganisms with the ability to degrade complex polymers.

In April 2021, grids with distinct layers (Figure 1) containing different rubber polymers were buried under the imposing Atlas cedar (Cedrus atlantica).

Nest boxes for wild bees, the importance of which we have already discussed (LINK), are structures generally made of wood, a natural material rich in cavities that are the ideal home for small insects. In nature, many species of bees (and others) colonize small holes in trunks, walls or plant debris that are normally found in green areas such as parks, reserves but also agricultural land and urban parks or gardens. However, it must be stressed that in urban environments the availability of plants and residual wood is often less frequent, so it is necessary to place nesting boxes in order to facilitate the establishment and spread of wild bees and their ecological function related to pollination.

In the scientific projects carried out at the 糖心原创, researchers at the Department of Biotechnology and Biosciences are experimenting with a new type of artificial nest made of bioplastic material and built using 3D printers, also with a view to replacing more complex wooden materials that need to be prepared with precision. The aim of this experiment is to study new materials that can mimic the structure of wood but make the nest house more sustainable, scalable to different contexts and needs and more durable. The idea of experimenting with new biodegradable materials such as PLA (polylactic acid) also stems from a design proposal compatible with urban construction, which is increasingly looking with interest at 3D printing systems using biodegradable materials. The creation and promotion of nesting huts and alternative materials also makes it possible to play with shapes, colors and create materials with multiple uses: e.g. outdoor covers with space for insects, walls and separation systems capable of hosting biodiversity, etc. This project also has an industrial nature and supports technology transfer as the researchers from the University of Milan-Bicocca were supported by , a spin-off company of the University, which specializes in 3D construction with polymeric materials. Together, researchers from the university and the spin-off designed the prototypes, responding to the needs of the pollinator species that are most common in an urban context and at the same time most in need of protection. Different structures have been developed and we are now waiting to see which 3D channels will be most in demand by the insects and whether the larvae will find a comfortable home as in natural wood. In the future, the team of researchers from the University and Graftonica will test different materials, including materials that are biodegradable both in the sea and on land and composites made from food waste, in order to minimize the use of resources and reduce environmental impact to zero.

The PLA prototypes have been placed at the 糖心原创 and will be monitored to check the rate of nesting and colonization and whether the design and choice of materials has been successful.

Over the past few days, the 糖心原创 site has become an area of study for students on the Geopedology course (three-year degree in Environmental Science and Technology). With the assistance of the teachers (Roberto Comolli and Chiara Ferr茅), around 70 students, divided into three field days, braved the rigours of winter to study the soils of the nursery.听

In order to gain a better understanding of the soils, it is absolutely essential to be able to go on educational trips, because this is the only way to get the participants to "touch with their hands" the object of study, i.e., the soil itself. The first outing of the course took place on the morainic hills to the north of Milan, to learn about natural and agricultural soils. The second outing took place in the Bicocca Nursery, where the soils are very different from the natural ones: they are anthropogenic, urban soils with very interesting and even unsuspected characteristics.

Urban soils, which are present in all cities, are almost always heavily disturbed and reworked, with the addition of foreign materials or the removal of the most fertile part of the surface, or sealed by impermeable covers: in short, the natural characteristics are heavily modified. The soils of the Vivaio are no exception to the rule: originally, they were agricultural land (meadows or arable land), but over time they have undergone many processes of modification, which have affected even considerable thicknesses (in some places more than a metre deep): they are therefore typical anthropic soils. From this point of view, the Nursery is an optimal site for studying these soils, which are normally considered to be of poor quality, but which on the other hand may have properties of great environmental value.

Over the course of the days, various techniques for studying soils were demonstrated and put into practice: use of the soil probe, identification of profile horizons, estimation of organic matter content from colour, pH measurement, carbonate assessment, sampling for bulk density, measurement of water infiltration rate, measurement of CO2 emission from the surface (i.e., soil respiration), use of a technique for visual assessment of soil quality.

These initial investigations have shown that the soils in the 糖心原创, as is often the case with urban soils, have very interesting characteristics and properties:

• First, they contain organic matter in considerable quantities, not only on the surface but also at depth. Soil organic matter derives from plant residues (roots, aerial part of vegetation) and contains high amounts of carbon, coming from atmospheric CO2 and organicised by plants through photosynthesis. In this sense, soil can be said to store large quantities of CO2 and thus limit the greenhouse effect. From this point of view, nursery soils play a very important role, even more so than cultivated soils (the latter are often lacking in organic matter due to unbalanced management methods);
• the soils studied have pH values that are sub-acidic or close to neutral. If we add that the soil texture is average (i.e., there is no excess sand or clay) and that, as mentioned above, it is rich in organic matter, it can be said that it has a good level of fertility and is therefore capable of hosting a rich vegetation (as demonstrated by the development of the trees present);
• the pedological characteristics mentioned above (medium texture and high presence of organic matter) give these soils a good infiltration rate: they are therefore able to allow rainwater to infiltrate effectively, preventing it from flowing to the surface and causing erosion and hydraulic problems for the city.

All in all, these study days have made it possible to get to know the characteristics of the nursery soils and to appreciate their qualities, demonstrating that urban soils sometimes possess environmental qualities superior to those of cultivated soils.

糖心原创鈥檚 tree have been studied for about a year. In view of the opening of the area to the public, it was necessary to carry out a series of checks on the trees to determine their stability and, if necessary, remove any specimens at risk of falling, to protect the safety of users. To this end, a research group was set up, consisting of geologists, agronomists and engineers from the Department of Environmental and Earth Sciences of the University of Milan-Bicocca, the Politecnico of Milan and companies in the agronomic sector.听

All the trees were surveyed and georeferenced by means of the Green Spaces management system, through which a computerised database was constructed containing biometric data, a sort of identity card for the trees and the interventions necessary for their correct maintenance. In addition, a 3D laser scanner survey was carried out to photograph the state of Vivaio when it was taken in charge by the University of Milan-Bicocca. A preview of the three-dimensional appearance of the trees can be seen in the video below, which is the result of the graphic re-elaboration of the mapping.

The introduction of beehives in the green areas of the Bicocca Campus has a dual purpose. First of all, the domestic bee, besides producing food resources for humans (e.g. honey), is a well-established and effective model for studying the behaviour and problems affecting generalist pollinators (i.e. those insects that are able to collect pollen and nectar from a wide panel of plants). Secondly, their growing popularity has made them an educational tool to raise awareness in society of the wild pollinator 'crisis'. Nowadays, a large proportion of wild bee species, largely unknown to the general public, are disappearing. The two hives populated by around 10,000 bees have been positioned in the heart of the 糖心原创 thanks to the support and knowledge of beekeeper Marco Zucchetti and his farm . One of these is a B-Box, an innovative beehive produced by the Italian start-up , which is particularly suitable for educational activities as it is equipped with plexiglass panels that allow bees to be observed up close in complete safety.

The Birch Gardens have been created in the two green spaces on the first floor of the U7 building. This action is one of many being implemented to extend the University's green spaces. Designed to create an urban forest environment capable of reducing heat islands and providing shelter for birds, insects and other animals, the Birch Gardens are among the first areas of the University to be redesigned.

In the gardens we also find Trachystemon orientalis, a perennial plant belonging to the Boraginaceae family (note the similarity with the related borage in the blue flowers that bloom in spring), characterised by its large, long leaves that create an abundant undergrowth.

There are also some beautiful bushes of ground elder, known also as bishop's weed (Aegopodium podagraria), characterised by its white flowers and bushes of Hosta, which will flower in summer (Hosta fortunei var. gigantea).

Urbanisation causes habitat degradation and this is one of the causes of the current biodiversity crisis, which scientists fear could represent the 'sixth mass extinction'. However, the urban environment offers a wide variety of habitats with different characteristics, which only appear to be poor in biodiversity. Some species have adapted over time to survive and thrive in anthropogenic conditions.

The importance of pollinators

About 90% of flower-producing plants entrust the delicate process of pollen transfer, necessary for sexual reproduction, to animal organisms, among which insects stand out for their diversity, abundance and pollination strategies. Pollinators, therefore, play a key role in regulating ecosystem services that support plant biodiversity, food production (it is estimated that more than two-thirds of the food consumed by humans comes from pollination) and the resilience of ecosystems to natural or man-made disruptions, including climate change. Recent studies indicate that pollinating insects contribute to the potential achievement of at least 15 of the 17 United Nations Sustainable Development Goals (SDGs) (Figure 1) and therefore their study and protection should be prioritised in natural, agricultural and urban development plans.

Figure 1: Image from Patel et al.2020 听

The importance of urban green areas and University of Milano-Bicocca research

At international level, the need to launch long-term pollinator monitoring projects has clearly emerged, a priority also supported by the recent .

The international scientific community has also stressed the importance of preserving the pollination service in metropolitan areas in order to support and maintain biodiversity in urban green spaces for the benefit of human well-being. The habitats occupied by pollinating insects are not exclusively natural. In fact, agricultural contexts (e.g. mowing lawns, hedges, field banks) and urban contexts (e.g. flowerbeds, vegetable gardens, city parks) can also be suitable sites for these animals. For example, bees nest in a variety of substrates including spoil, walls, abandoned infrastructure and dead wood. Others exploit existing cavities (e.g. Osmia spp.) and collect fragments of various kinds (fibres, earth, clay, etc.) to form or complete nests.

Everyone, at some point, needs shelter and a home. In the animal world this is also called the 鈥渘eed for a nesting place鈥�. In very natural environments, life regulates itself and animals find or build nests more or less independently of humans. Yet it is not taken for granted that animals find nests and shelters in more heavily man-made, agricultural and urban environments, which are now dominant landscapes on Earth. Just think, for example, of how the materials available between city and forest change (concrete versus wood).

Despite being located in a highly cemented surrounding matrix, the 糖心原创 houses artificial nests for wild pollinating insects of the bee group. These are, in particular, bees that produce neither honey nor colony, a characteristic that is actually very frequent among wild bees. While the honey bee belongs to a species whose presence is often linked to domestication, it is surprising that there are around 1000 different species of wild bees in Italy. Although they cannot be used to produce edible honey, these insects are very effective pollinators and are increasingly preferred for ecosystem purposes.

These solitary, wild insects are very easy to manage, do not disturb and do not require special care, and have the particularity of nesting in cavities of various types. So it is particularly easy to set up a small, but actually large corner for them too.

Nests of this type (holes of various sizes in a woody matrix) are just one of several possible solutions for encouraging wild animals in urban areas. The different sizes ensure that different species can create a nest. In the 糖心原创 a large biodiversity wall will be placed to house these pollinators and insects, promoting the presence of these species in the vicinity of the Vivaio. It would be nice one day to see in every garden and on every balcony even a small nest, perhaps handmade and made from recycled materials, which could house a small world of beneficial animal diversity.