At the heart of plant conservation: The work of Tania Walisch

Tania Walisch explains her research on threatened plants, the value of biodiversity databases, and how everyone can take action to help preserve nature.

A biologist at the National Museum of Natural History Luxembourg (MNHNL), Tania Walisch dedicates her work to the study and conservation of threatened plants. Balancing scientific research, databases, and fieldwork, she strives to safeguard plant biodiversity in Luxembourg and beyond.

Tania, can you tell us about your career at the Musée national d’histoire naturelle?

I joined the Naturmusée in the late 1990s, initially as a research assistant in the Department of Botany and Ecology. This formative first experience shaped the trajectory of my career.

Alongside a part-time position as a biologist in a consulting firm, I pursued a PhD in population biology, a research field directly inspired by my work at MNHNL. I focused on studying the effects of habitat fragmentation on Meadow Saxifrage and Rhine Saxifrage on rocky outcrops.

In 2000, I joined MNHNL permanently as part of a new department dedicated to population biology and databases. This marked the beginning of a long professional journey at the museum, which continues to this day.

What does your work involve today?

My training is primarily in plant ecology and population biology. In the early 2000s, however, biodiversity databases were booming. MNHNL quickly recognized the strategic importance of these tools, and I became heavily involved in their development.

For nearly twenty years, I managed the national database on plant and animal biodiversity. It compiles observations of plants, as well as animals and fungi, contributed by MNHNL researchers, consulting firms, government agencies, and citizen science projects. In doing so, MNHNL became a central player in biodiversity data in Luxembourg.

At the same time, I contributed to the development of the museum’s collection management databases, particularly for complex taxonomic questions. As the amount of data, stakeholders, and digital tools increased, the team had to be expanded, which allowed me to refocus more on scientific research.

What does your research in population biology involve?

Population biology studies the functioning of groups of individuals of the same species. My work focuses on threatened or declining plant species, aiming to understand their needs, the causes of their decline, and conservation possibilities.

Practically, this involves extensive fieldwork. I study different populations of a species: their size, age structure, dynamics, and genetic diversity. Genetic diversity is crucial because it determines a species’ ability to adapt to environmental changes.

I also analyse the effects of habitat fragmentation, which isolates populations, limits genetic exchange, and increases the risk of inbreeding.

You’ve worked on Rhine Saxifrage for a long time. Why this species?

Rhine Saxifrage (Saxifraga rosacea sponhemica) is an emblematic species. It belongs to a small group of species for which Luxembourg bears significant international responsibility: about a quarter of the world’s known populations are found in our territory.

It is a relict of glacial periods, now living in very specific conditions: on cool rocks, neither too shaded nor too exposed to the sun, such as at Vianden. When I began working on it, little was known about its ecology. It remains largely unknown to the public, despite being both very beautiful and highly distinctive.

Why is it important to conserve such a rare species?

Even if Rhine Saxifrage has no direct use for humans, it plays a role in its ecosystem, like any species. Every species interacts with others and contributes to the overall balance of natural habitats.

The richer an ecosystem is in species, the more resilient it is. Conservation should not be limited to “useful” species but aim to preserve biodiversity as a whole.

Since 2020, I have been coordinating, together with the Our and Haute-Sûre nature parks, an active conservation project for Rhine Saxifrage. We introduced new populations at several sites in the north of the country, testing various methods: sowing, planting young seedlings, and varying the genetic diversity of the material used.

Preliminary results show that about 20% of plants survive after one year. We also observed that combining sowing and planting seedlings works better than either method alone, as they respond differently to climatic conditions.

This hands-on project helps identify the most effective strategies for introducing new populations and preserving existing ones. Notably, despite habitat fragmentation, Rhine Saxifrage maintains high genetic diversity due to both its longevity and a remarkable genetic trait: it is polyploid, meaning it carries multiple copies of its genome – a major advantage for preserving genetic diversity.

Our work has also drawn the attention of botanical conservatories in France, with whom we are now collaborating to develop a National Action Plan for the species, which is even rarer in France than in Luxembourg.

How do habitat fragmentation and changes in land use impact vegetation?

Habitat fragmentation reduces and isolates favorable environments for plant species.

Populations become smaller and more scattered. Isolation limits genetic exchange, increasing the risk of inbreeding and genetic drift, weakening long-term population viability. Pollinator decline adds to this effect: small plant populations are less attractive and visited less frequently, reducing reproduction and creating a vicious cycle of decline.

The main cause of this fragmentation is agricultural intensification, which began in the 1950s. Flower-rich meadows were replaced by silage meadows consisting of only a few grass species. These function like monocultures, leaving little room for plant diversity.

Extensive use of fertilizers is another major factor. Fertilizers favor grasses that thrive in nutrient-rich soils, while many herbaceous species decline. When grasses grow densely and competitively, more demanding species cannot survive, sometimes leaving only older plants that cannot reproduce, leading to gradual extinction.

Additionally, abandoned low-productivity agricultural lands have become overgrown. This affects various habitats: pastures, hay meadows, dry grasslands (increasingly rare), and drained wetlands. These changes have profoundly altered landscapes and ecosystems.

Urbanization exacerbates the problem by sealing soils, permanently destroying natural habitats and further fragmenting environments.

If you could concentrate maximum resources on saving one plant species, which would you choose and why?

It’s a difficult question, because a species cannot survive alone. Biodiversity works as a network of interactions. Saving a single species without preserving its habitat and surrounding organisms makes little sense.

The main goal is to preserve genetic and ecological diversity, both at the species and population levels, to maximize adaptability to changes, including climate change. Local variation between sites forms the foundation for population adaptation and species’ genetic richness.

Rather than choosing a single species, I would focus on preserving as much diversity as possible, as it underpins resilience.

Beyond creating nature reserves, Luxembourg has implemented extensification contracts encouraging less intensive farming to preserve habitats and rare species.

Farmers managing eligible plots must avoid fertilizers, pesticides, or chemicals outside of manure. For hay meadows, mowing is delayed (after June 15, or after July 15 for certain habitats) to allow flowering plants to complete their cycles and produce seeds.

What can the public do to help protect threatened plants?

Become interested. Learn to recognize plants around your home, in your garden, or in everyday landscapes. Smartphone apps now make it easy to familiarize yourself with local flora.

Visit the  Flora Fabulosa, dexhibition (March 5–23 at the Erwuessebildung, 

which tells surprising stories about Luxembourg’s wild plants – I was delighted to collaborate on it. Explore the museum garden and permanent exhibition, featuring biodiversity and plant-animal adaptation, to understand what protects or threatens biodiversity and the solutions available.

Visiting nature reserves is another option. They often feature educational trails dedicated to plant diversity or specific groups like orchids. These sites inspire wonder while highlighting species’ needs and conservation challenges.

Local engagement is also possible. Nature protection associations, sometimes organized locally, welcome volunteers, or one can start a local initiative. Even simple engagement – enjoying nature, appreciating biodiversity, and reflecting on lifestyle changes that leave space for other living beings – matters.

Consumption choices are crucial. Consume less, choose organic, and support production methods that preserve biodiversity. Organic and regenerative agriculture positively impact biodiversity compared to intensive practices. Reducing meat consumption also helps, as everything is interconnected: biodiversity, climate, and land use.

Finally, participate in concrete habitat restoration actions whenever possible.

What inspired you to work on the conservation of threatened plants?

It started in primary school with a passionate teacher who generously shared her knowledge of wild plants, and on walks with my grandmother, who collected plants for infusions. I have always been drawn to plants, wanting to know their names and understand them better.
Later, in high school, a documentary on climate change was decisive. It sparked my desire to engage in environmental sciences, naturally leading me to plant-related disciplines.

How do you communicate these issues to the public?

Through multiple channels: MNHNL exhibitions, collaborations with nature parks, scientific publications, and participatory projects like the City Nature Challenge or Biodiversity Days.

During the Biodiversity Weekend in June 2025, for example, colleagues and I accidentally rediscovered a species thought extinct in Luxembourg (Parietaria officinalis) just 200 meters from the museum!

These initiatives allow the public to explore local biodiversity, understand scientific methods, and sometimes contribute directly to research.

What are your future projects?

We plan an experiment in the MNHNL garden to study the effects of climate change on Rhine Saxifrage. The goal is to identify individuals or populations better adapted to drought. Seeds from all regions where the species still exists will undergo prolonged water stress, and their responses will be compared to unstressed plants. This will help us understand population resilience and develop concrete conservation actions, supported by international scientific collaboration.

I also plan to study population biology of other priority species for conservation in Luxembourg and internationally, including Grenoble Pink (Dianthus gratianopolitanus), a heritage rock-dwelling species.

Together with MNHNL colleagues, we are launching a project with the Nature and Forest Administration to assess populations of priority species and implement conservation actions in nationally protected areas.

Finally, I aim to explore drone use for monitoring and conserving threatened plant populations on rocky outcrops.

Interview: Diane Bertel

Editors: Monique Kirsch, Selma Weber (MNHNL)