Species loss is progressing rapidly. Humans are responsible for the sixth mass extinction in the planet's history. With the help of local residents, researchers want to prevent this mass extinction and preserve certain plant species that are native to the dry grasslands of Berlin and Brandenburg.

The delicate little plants are just a few days and weeks old. In the seed pods the seeds are huddling together. Tens of thousands of plants, of about 30 different species, are growing here in seed trays at a testing site at the University of Potsdam's Botanical Gardens. Ariella Zacharia and Jonathan Neumann carefully remove each seedling from the earth. The little plants need more space, so today they are being repotted. The two prospective biologists, who are working as student researchers on the project 'Urbanity and Diversity', call this 'piquing'. They are working very cautiously as the plants they are pulling up are quite special: they all belong to Brandenburg's rare and endangered species. As soon as they are a little stronger, they will be taken over and cared for by plant-parents in Berlin and Brandenburg, and allowed to grow and thrive on balconies and in urban gardens.

The Bristly Hawkbit, the Dwarf Everlast flower, the Carline Thistle and the Schiller Grass (a species of Junegrass) – all of these plants have lost large swathes of their habitat over the last few decades. The project 'Urbanity and Diversity' brings science and the public sphere together to create new refuges for the endangered plants – primarily in the city. "This is nature conservation, concretely and practically," says coordinator Gesa Domes of the project, which began in 2017 and has since arranged more than 1000 plant adoptions. "Everyone can get involved," she says. In addition to those in Berlin and Brandenburg, there are also active partner projects in Dresden and Marburg.

In the inner courtyard of a Berlin housing collective, on private balconies, in urban gardens, and in orchards cared for by the conservation group NABU, the project's botanical treasures are already growing. These plants have become increasingly rare and have very special requirements: they like it dry and nutrient-poor, only then can they assert themselves against other species. Botanists call this plant community the dry grasses, originally a result of goat and sheep grazing on the sandy, poor soils of the Mark. "In Berlin and Brandenburg in particular, these kinds of habitats are threatened by changing agricultural practices," explains project coordinator Christian Schwarz. "Urban spaces could become retreats for these species," hopes the biologist.

Researchers, with the help of local residents, have taken 34 species under their wing, to help them propagate and thus help to preserve their existence. Among these are species that allure with their beautiful flowers, such as Blue Bonnets and the white-blooming Grass Lilies, which potential plant-parents are easily excited about. Though also some unspectacular plants – such as various grasses or the Spanish Catchfly plant – have already conquered flower boxes and gardens around Berlin and Potsdam. "People want to garden in a natural way and do something for biodiversity. There is a lot of interest," says Gesa Domes.

The plants also grow in small garden beds in the project's so called 'arc area', in the Jelena-Šantić-Peace Park in Berlin-Hellersdorf, where they can be admired and cared for. Environmental educational projects also take place here, conveying information about these rare plants and their protection. "You can only protect and value things that you know," explains Gesa Domes. "That's why it's also so important to be familiar with these species, otherwise no one really knows what is lost." Anyone who has these endangered plants right in front of their door or window, they see, feel, sense, and are motivated to protect these plants in the long term. There are also excursions into the natural habitats of the plants, lectures and workshops.

By now, the project can count on a good network of 'true blue plant saviours' - they raise the plants, they harvest the seeds from which new plants are grown and also help to reintroduce the young plants into suitable locations. In this way more than 10,000 plants have already made the leap from the balcony back into nature and now grow in wild meadows, parks and nature reserves. How many of the plants survive in these locations and are able to propagate, and which species in particular can profit will be scientifically analysed. Which soil properties and environmental conditions promote the success of their release into nature and further growth? The researchers are also investigating whether there are genetic changes in the plants caused by their propagation and cultivation. "With rare species in particular, genetic diversity is incredibly important and often inadequately researched," explains Christian Schwarzer. For this reason, the seeds, which are collected in close consultation with nature conservation authorities, come from local sources so that they are optimally adapted to the respective locations.

For the project coordinator, the conservation of biodiversity has not only an idealistic and ethical value, but also a very tangible economic one. The pollination of agricultural crops and therefore the harvesting of fruit and vegetables, clean drinking water and clean air – all this is only possible when nutrient and water cycles function and ecosystems are intact. 'Ecosystem services' is the technical term used to describe these services, provided freely by nature. The fewer species that live in an ecosystem, the more susceptible it is to disturbances such as disease or climate change. "Everything is closely intertwined, and without diversity it doesn't work," stresses Gesa Domes. Just as certain kinds of butterflies or wild bees, for instance, are dependent on very specific plant species. When these disappear, the insects have no chance of survival either.

Anyone who decides to adopt one of these plants not only receives the young plant for free, they also receive an information booklet on the plant's characteristics and care instructions. In case anything goes wrong and the seedling does not want to grow in the planter on the balcony "it's also not so bad," says Gesa Domes. "But, of course, we also try to avoid mistakes with comprehensive instructions and preparation." The plant-parents learn, for example, the preferred location for the particular plant, how the soil and planter should be arranged and how to best collect the seeds. Strictly protected varieties are grown exclusively in the arc area and the testing site at the Botanical Gardens.

For the final two years of the project until the end of 2022, Gesa Domes and Christian Schwarzer are hoping to open a door of communication with Berlin's allotment gardeners in particular. "Here you can often find large, connected areas of land, on which several hundred plants of the same species grow across multiple parcels and exchange genetic information. This offers even more possibilities for conservation." In a large planting operation, the plant species are selected and moved to planter beds together. The project team gives tips on how to collect the seeds, and eventually this should lead to the sprouting of new seedlings.

Naturally the project team is hoping that the wild beauties of the dry grasses can find permanent homes in gardens and on balconies – even after the project has finished – and are conveying the knowledge needed to ensure this. Some species need light to germinate, for example, while others need frost. Each of the 34 varieties are fascinating in their own way, says Christian Schwarzer, although he is particularly partial to the Blue Bonnet, with its tender blue flowers. "It not only has an especially beautiful bloom, but it also often attracts really great insects. Which ones exactly, though, I'm still learning myself," he says, laughing.

The 'Urbanity and Diversity' project is funded by the Federal Agency for Nature Conservation using funds from the Federal Ministry for the Environment, Nature Conservation, Building and Nuclear Safety, as well as by the Saxon State Ministry for Environment and Agriculture, the Brandenburg State Environment Agency and the City of Marburg.