A wake-up call for the protection of insects

Autumn 2017. The so-called ‘Krefeld Study’ is published, and as a result something happens that no previous comparable study or Red List of threatened species has ever brought about: the issue of ‘insect decline’ captures the public’s attention and sparks a renewed commitment to protecting insects and their habitats. However, this comes in the wake of some bad news: as of 2017, the biomass of flying insects in certain nature reserves had declined by more than 75 per cent over the preceding 27 years. This grim news sets a number of developments in motion. You may have already heard about the successful referendum in Bavaria on biodiversity. This was followed by similar initiatives in other federal states, and monitoring programmes were launched to track long-term trends, investigate the causes of insect decline and develop effective measures. A national monitoring centre and an Insect Protection Act have even been established.

Insect monitoring: not just for researchers

Even amongst the general public, enthusiasm for insect conservation has grown, and citizen science-based projects have gained popularity. Through these projects, anyone – whether an insect expert or simply a nature lover – can collect data and help to expand our knowledge of the distribution and abundance of insects. Even the famous Krefeld study was compiled using the results of years of citizen science. Identification guides, such as those for wild bees and wasps in nesting aids, play a crucial role in this, but more on that later.

Why are wild bees and wasps so important?

The protagonists of this identification guide also play a key role, as they fulfil vital ecosystem functions – such as pollination and pest control – and are therefore essential for maintaining stable ecosystems. Let’s first take a closer look at the more than 600 species of wild bees in Germany. Many of them act as vital pollinators in their habitats. But that’s not ‘all’! At the same time, they make a significant contribution to ensuring we have a varied diet, as over 70 per cent of all crop species rely either partly or entirely on pollination by insects. In practical terms, this means that if there were no more insects, we would, for example, have significantly lower yields of our strawberries, cherries, pumpkins and tomatoes in this country.

The introduction to the identification key explains:

“While wild bees, as furry pollinators, are widely admired in society, many people often associate the term ‘wasps’ with unwelcome guests who become a nuisance whilst we’re eating cake in late summer. But if we look beyond our own plate, we see that stinger-bearing (aculeate) wasps are valuable natural pest controllers. This is because, depending on the species, wasp larvae are fed on beetle larvae, butterfly caterpillars or aphids, for example.”

The latest Red List of threatened species highlights just how important it is to protect these animals. According to the list, around half of all bee species and 46 per cent of the 630 stinging wasp species in Germany are considered endangered, if not already extinct. At the same time, the data available is patchy. This makes it all the more important to raise public awareness of the taxonomic expertise relating to these species. Yet this expertise is currently lacking amongst the general public.

It’s not just insects that are lacking these days…

… but also to the people who can identify them. This is demonstrated by the European Red List of insect taxonomists. Yet the conservation of biodiversity absolutely requires many people who are knowledgeable about the species – who can identify them scientifically and accurately, understand their phylogenetic relationships and ecological roles, and are able to assess their conservation status. In recent decades, not only has the number of species declined, but so too has the number of taxonomists, meaning that their expertise is now concentrated in the hands of a few individuals. The Red List of Insect Taxonomists is a call to all experts to share their knowledge of species with the wider community, as well as a call to the general public to recognise the importance of taxonomy and to ensure its long-term survival. This is precisely where identification guides come in!

And that brings us back to our guide to identifying wild bees and wasps in nesting aids.

How the identification guide guides

First and foremost, it helps us to make biodiversity visible. Whilst many people are already aware of the importance of wild bees and wasps, many species remain invisible to the untrained eye. The key word here is ‘still’, because the identification guide brings these species out of hiding and gives you more practice in recognising and identifying them.

It is not only wild bees and wasps that play a central role in these small ecosystems. Their antagonists – natural predators such as cuckoo wasps and  fruit flies – are also vital for maintaining the ecological balance. That is why the guide also highlights them, thereby providing the user with a complete picture of what is happening inside the nesting aids.

Speaking of nesting aids!

Why insects – and therefore we too – need them was probably made clear right at the start of this article: highly specialised species, such as wasps and wild bees, are in sharp decline.

But why is that, exactly?

Our landscapes were once adorned by a diverse mosaic of pastures, meadows, arable land and fallow fields, dotted with hedgerows and copses – perfect nesting conditions for the group of aculeata, to which wild bees and wasps belong. Yet today, the landscape often looks very different. Monotonous landscapes stretch as far as the eye can see, where intensive land use and fragmentation, chemical fertilisers and intensive animal and plant breeding have caused key elements for biodiversity to disappear. This includes nesting opportunities. That is why nesting aids offer a whole host of benefits. Not only are they a valuable tool for research, monitoring and environmental education, but they are also used as breeding habitats by around 8 per cent of the wild bees native to Germany and as many as 19 per cent of wasp species! Thus, nesting aids – including the identification guides that accompany them – make an important contribution to the conservation of these small creatures and to a better understanding of their diversity, food resources and trophic interactions.

And here’s how you can contribute as well:

1. Download the identification guide here (but note that it’s only available in German).
2. Take it with you to the nearest nesting box in your garden or elsewhere and check it there.
3. Very important: share your findings! Many nature conservation initiatives collect observation data, and the insights you gain from identifying species can contribute to local species lists and conservation measures. The fact that this guide is partly the result of the ‘Nesting Aid Sponsorship’ citizen science project highlights just how important the involvement of volunteers is.

More than a specialist book

Ultimately, this guide is not only a key to identification, but also your key to the fascinating world of wild bees, wasps and their natural enemies. Whether you’re a beginner or an experienced observer of nesting aids, this guide will help you discover the biodiversity of these important insects in your local area, understand them better and, last but not least, contribute to their protection. The more people who immerse themselves in this world, the shorter the Red List of insect taxonomists will become. So: head out into the countryside and have fun getting to know and protecting Germany’s cavity-nesting wild bees and wasps!

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Citation:
Grabener, S*., Lindermann, L*., Schiele, S*., Bendixen, L., Fornoff, F., Hopfenmüller, S., Stahl, J., Dieker, P. (2025) Wildbienen und Wespen in Nisthilfen bestimmen: ein Bestimmungsschlüssel für Deutschland. 2., vollst. überarb. Neuaufl. Thünen Ratgeber 10. Johann Heinrich von Thünen-Institut, Braunschweig. https://doi. org/10.3220/253-2025 168

*Lead authors

All the photos are taken from the identification guide; the photographers are listed on the last page.

“If you want to go fast – go alone. If you want to go far – go together.”

– origin unknown, often attributed to an African proverb

There is something very exciting going on in the realms of ecosystem restoration and you (yes, you!) should know about it! Last year, the research team of A living lab for social-ecological restoration in western Rwanda, part of a larger project dedicated to social-ecological systems informing ecosystem restoration in rural Africa, launched its living lab in Rutsiro.

There’s even an article on this blog about the launch! You’ll find it here along with more info on the background and the previous stages of the project (it might be helpful to read that article first to get the full picture). But now, let’s catch you up on recent happenings and give you a glimpse of what’s in store for the project’s future. So, lean back and enjoy the journey through the process of the living lab in Rutsiro!

A quick recap anyway

If you’ve read the launch article, you’ll know that the living lab is all about bridging science and practice in Rwanda’s efforts for ecosystem restoration and reconnecting local communities with native tree species within an Agroforestry setting. For that, the team is following a process of co-creation to implement social-ecological experiments on farmers’ land in Rutsiro, that essentially involves planting trees as part of an Agroforestry approach to restoration.

Who is behind the team? There are around 50 transdisciplinary stakeholders from across sectors working together in two different roundtables, each of which is based on two governance models, each representing a distinct restoration community of practice. One group is NGO-driven, uniting representative restoration actors from government, NGOs, academia and the private sector. The other one is almost entirely farmer-driven: local farmers, who are also traditional healers, beekeepers, teachers or carpenters, alongside community leaders and local extension officers.

The communities have been involved in regular workshop sessions in which members first started by establishing codes of conduct, strategies on how to communicate, expectations and potential contributions. What’s especially interesting for us now is what happened in the last workshops in February this year.

Setting the scene: The grand selection of tree species

In February, each group had a workshop in which they co-designed the restoration experiments by ranking and prioritizing the native and exotic trees species suitable for the area for the restoration experiments. As a result, both governance models now have a list of prioritized tree species. These species are around 80 % native and 20 % exotic, which is quite radically different compared to the fact, that so far, most trees planted in western Rwanda are not native, which leads to loss of biodiversity and ecosystem services and depauperate landscapes (Nyiramvuyekure et al. 2026).

Interestingly, the two groups did the same workshops in parallel, but came up with a slightly different list of tree species they want to plant. Each governance model is assigned to a specific region with living lab sites having been selected for doing the restoration experiments – including the tree planting.

Let us walk you through the workshop day by day

William Apollinaire, Vicky Temperton and (for one day) Stefan Sieber attended the workshops, as scientists and principle investigators of the Rwanda research project.

The first day of the workshop – held on separate dates for each governance model – took place in a conference room. This was where the magic of selecting and prioritizing the tree species happened based on the values stakeholders assigned to each species. The values ranged from ecological to socioeconomic criteria, survival rates, availability of planting material and compatibility with the most commonly grown crops in western Rwanda. At the end, the ranked list of tree species the groups want to plant saw the light of day.

Enjoy the following impressions of how the first day looked like for both governance models:

The next day, the groups got into action out in the field. They went out to their living lab sites and met with the local landowners of the land where the trees are going to be planted, including meeting up with scientists involved in the research project, some of whom were visiting the living lab to connect to this aspect of the overall research project.

These field meetings were crucial, first for the communities to connect to the scientists but also to agree with landowners on the selected species as well as the proportion of native and exotic species to be used in the living lab experiments. After some comments, suggestions and adjustments, a final agreement was reached. And there it was – the blueprint of the living lab experiments, co-created between local stakeholders and scientists!

Impressions of the second day out in the fields:

What made these workshops special

“I can see the momentum!” – Dr. William Apollinaire

Not only was this trip key in determining the ongoing process of the restoration experiments, but it was also, and maybe even first and foremost, very valuable in terms of interpersonal exchange. When you hear Dr. William Apollinaire, the Postdoc researcher and coordinator of the living lab research in western Rwanda, speaking about his highlights of the workshops in February, it soon becomes clear that the workshops as well as the whole process mean a lot to everyone who is involved in the living lab. The true jewel was seeing how much the stakeholders are engaged. The participatory process, the involvement and empowerment of the people. Moments like spontaneously singing and dancing together, enjoying and exchanging cultural aspects. All of this leads to a successful co-creation. According to Dr. William Apollinaire, the stakeholders are fully engaged and eager to see the outcome of the living lab. “It was interesting to see how, if people are empowered enough, they can engage actively in the collaborative or participatory process.”

But how do you get to this point of engagement?

“Bringing people together with other stakeholders and sharing the same meal, the same treatment.” – Dr. William Apollinaire

It wasn’t difficult to get people on board and sustain their engagement long-term, as the initiators of the living lab selected people for the roundtable who have already been involved in restoration activities. The key, however, is to value everyone who is part of the process. To value everyone’s voice. This way, an empowering environment was created in which every stakeholder could feel respected. Part of this is also organizing the logistics to make sure that everyone is involved, for instance, by facilitating communication. Understanding everyone’s expectations and goals. Every stakeholder being part of the design as well as the planning and implementation process: That is how co-creation works. That is how this momentum of engagement came to life.

What’s in store for the future

Now you know what’s currently going on in the living lab, but we certainly don’t want to withhold the exciting next steps that are coming up our way. Right at this moment, the trees, which the two governance models have decided on, are developing in a nursery of local restoration stakeholders. They are growing and waiting to be planted in October this year, but before the planting happens, the farmers will learn how to prepare the land for the planting in September. The kick-off of the planting campaign in October will be a big event where the trees will go into the ground and we’re going to hear different speeches from people from the government and local communities. Excitingly, the national media is going to be invited to cover the event and who knows, maybe you might even read an article about it on this blog, so stay tuned!

While the trees are growing

In the meantime, the stakeholders will, together with the scientists, define socio-ecological indicators of success to be measured during the experiments and how those are going to be monitored. Examples of these indicators of success might be improving the nutrition of local communities as well as reducing medical costs. Ecosystem restoration is not just about the trees but also about shrubs and other plants that are incorporated alongside them, with nutritional and medicinal value. Species that have these values and are going to be planted include, for instance, Albizia gummifera, Carapa grandiflora, Vernonia amygdalina, Milletia dura, Ricinus communis, passion fruit, local papaya, avocado, lemon, myrianthus, and chayote.

“Everyone is excited about the book” – Dr. William Apollinaire

Attention! The initiators of the living lab are also writing a book about agroforestry trees in Western Rwanda and their many benefits and uses. It will highlight especially native species and their potential but also include non-native species which are still useful for ecosystem restoration. Watch this space in the future for more information on the book. The aim in publishing this book is to contribute to connecting local people and NGOs to the wide array of, especially native trees they have in at their disposal.

What happens after the planting?

Don’t forget that the planting of around 80 % native species in the experiments is very different to the usual non-native tree planting in Western Rwanda. Therefore, it will be very interesting to see the outcome of the experiments. After some time, the two governance models will be compared, and the stakeholders will continue to be engaged by learning how to monitor the sites. The overarching goal is for the communities to have full ownership of the restoration in the end and that they keep monitoring it themselves in the future.

There’s one last thing we want to give you to take with you on your way

Let’s go back to this sentence you already read at the beginning:

“If you want to go fast – go alone. If you want to go far – go together.”

As you probably noticed from this article, the co-creation of ecosystem restoration is, most importantly, a joint learning process. This might take a long time. But it will be most definitely worth it! Only by including everyone involved, designing and walking the path together, will the outcome match what everyone envisioned. Or, to say it in the words of Dr. William Apollinare: “That is how we achieve success in scaling up and upgrading the restoration experiments from research to practice!”.

Thank you for reading and hopefully, you’ll be back for the next update of the living lab in Rutsiro!

If we’ve now caught your interest on ecosystem restoration in general and in Western Rwanda, we highly recommend you this article of the Social-ecological Systems Institute of Leuphana about the five critical frontiers for science and practice of ecosystem restoration in East African landscapes: From Local Knowledge to Restoration Practice: Five Critical Frontiers for East African Landscapes | Ideas for Sustainability. It references a research paper recently published by the living lab’s research team.

Literature:
Nyiramvuyekure, V., Fischer, J., Kaplin, B. A., Mukuralinda, A., & Temperton, V. M. (2026). Woody vegetation diversity remains low after extensive forest landscape restoration efforts in a western Rwandan landscape. Biological Conservation, 317, 111812. https://doi.org/10.1016/j.biocon.2026.111812

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“Homogenisation of mountain ecosystems through non-native species?” No idea about that…

Then let’s start with the background: While humans expand into natural environments, global transportation networks lead non-native species to not only spread throughout the globe at an increasing rate, but also to expand upwards. As this article already gave away, the spread of non-native species increases the risk of homogenisation for plant communities, which means a reduction of diversity between communities. Potential consequences are decreased landscape variability and ecosystem services. For us, this urgently calls for action to conserve diverse communities. Particularly for mountain regions, the long-term effects of homogenisation are poorly understood and there aren’t a lot of studies comparing multiple scales for higher elevation. Luckily for us, Buhaly and colleagues aimed to kick-start filling this research gap with their study.

The study design and vegetation surveys in numbers

To determine whether the addition of non-native species leads to homogenisation or differentiation, the researchers addressed local, regional, continental and global scales by looking at the dissimilarity, i.e. beta-diversity, between plant communities along mountain gradients. Why did they specifically look at plants at mountain roads? Because roads represent the transition where non-native species can spread from low to high elevations.

Now, are you ready for some interesting numbers?

• 18 mountainous regions from all continents (except Antarctica) were surveyed for vegetation data, along 46 mountain roads.
• 2012 to 2023 was the timeframe in which the datasets were collected.
• 1 to 4 elevation gradients were selected per region, with each elevation gradient divided into 20 equal sampling sites.
• This added up to 687 sampling sites across all regions in total, in which 2627 native and 563 non-native species of vascular plants were identified.

In case you want more details, here is an explanation of the figure:
Local scale: Analysis of sites within same elevational band separately for each elevation gradient within each region. Regional scale: Analysis of sites within same elevational band across elevation gradients within each region. Continental scale: Analysis of sites within same elevation band across elevation gradients in same continent. Global scale: Analysis of all sites in same elevation band for all elevation gradients.

The results we’ve been waiting for: Homogenisation or differentiation, or both?

First of all, across all regions, non-native species richness declined with increasing elevation. At the global scale, the researchers found homogenisation of communities by non-native species. From the local to continental scales, however, they found both homogenisation and differentiation.

Looking at different scales matters

As you can see in the figure above, surprisingly, community homogenisation and differentiation were balanced across continents. The researchers also found striking differences at regional and local levels between the American continents, where homogenisation dominated, and Asia, Africa, and Europe, where non-native species led to community differentiation.

These findings suggest that homogenisation through the addition of non-native species may not be as common as originally thought, especially when looking at smaller scales.

A word on elevations

Most of the regions show homogenisation through species invasions at low elevations, where non-native species are most abundant. But the results suggest that as non-native species continue to move upwards, due to climate warming and road networks, high elevation communities may also become increasingly similar in the future.

No single mechanism explains everything

Clearly, the effects of non-native species vary with region, elevation, and scale. Homogenisation and differentiation are driven by interconnected mechanisms such as invasion history, species frequency, environmental filtering, and human land use.

What do we to take away from this?

Most importantly, the addition of non-native species can contribute to homogenisation of roadside plant communities, especially at a global level. This is partly driven by the number of non-native species, but also by their frequency across multiple sites. The observed homogenisation in the study mainly results from the addition of the same non-native species, across regions, not from immediate loss of native species. Homogenisation through the replacement of native species, though not studied here, can also lead to possible risks to ecosystem functions and community resilience of plants.

Remember the plot twist of the study’s findings: There wasn’t only homogenisation, but also differentiation. We must keep in mind that the exact impact of homogenisation, differentiation and the transition between these two stages is not yet well known. Nonetheless, community differentiation through the addition of non-native species may also be beneficial. With the increasing impacts of climate change, non-native species can potentially increase functional resiliency of plant communities. But beware of the risks of the invasion of non-native species!

Our main take-away: Global homogenisation might be a signal that high-elevation plant communities along roadways may become more similar as non-native species continue to spread upwards.

A look into the future

This study provides us with the first global assessment of how non-native plants affect mountain plant community similarity along elevation gradients. In the future we need studies to investigate what mechanisms might drive homogenisation and differentiation by non-native species and what potential consequences for ecosystem function and resilience they have.

To be continued…

You want to learn more about the impact of non-native species on plant communities in mountain regions and the study’s findings? Then read the full article here: https://onlinelibrary.wiley.com/doi/10.1111/geb.70137

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A recently published study by Michael Staab, Professor of Animal Ecology and Trophic Interactions at the Institute of Ecology at Leuphana University, and colleagues investigated if restoring grasslands by reducing land use can support insect abundance and diversity.

Exploring biodiversity experiments: The design of the study

Staab et al. investigated the effect of land-use intensity on invertebrates using a newly established extensification experiment that is part of the Biodiversity Exploratories. This framework was used for understanding how the effects of reduced land use depend on local contexts as well as specific management decisions, which are all part of land use.

How did they find out what’s really the case? The study was conducted at 45 grassland sites across three different regions in Germany. At each site, the researchers compared a regularly managed control plot with a nearby treatment plot with experimentally reduced land use, meaning only a single late mowing per year and no fertilization or grazing. In 2021 and 2023, one and three years after the experiment began, invertebrates were collected on both plots. In 2021, the samples were identified using DNA metabarcoding, allowing a thorough species identification. The team then analysed differences in abundance, diversity and species composition, and tested how factors such as mowing frequency, fertilization and mowing technique in the surrounding matrix as well as management decisions on the reduction plot influenced the magnitude of land-use reduction effects. Keep in mind for the results that there was no diversity data for the second sampling in 2023.

The results: Giving grasslands a break is a win for insect numbers

Reducing land use to one late mowing increased the abundance, so the number of individuals of invertebrates by 41 %. But wait, it gets better: After three years, the abundances in the reduced land-use plots were a full 99 % higher. However, the species richness, Shannon diversity and Simpson diversity between the treatment and the control plots were almost identical after one year. Consequently, the treatment effect of reduced land use had a positive, over time increasing effect on abundance of the invertebrates, but not on their diversity.

But that’s not the whole story. In both years, the magnitude of the treatment effects on abundance depended on the type of land use of the surrounding grassland and on how the plot with reduced land use had been mown in the previous year. The effects of land-use reduction were smaller when the surrounding area had previously been mown more frequently. In contrast, on more fertilized sites, the positive effect of extensification increased. The effect was also larger when the reduced land-use plot was mown with a greater cutting height and when the treatment and control plot were not mown on the same day.

We need to discuss some things:

Why an increase in abundance, but not in diversity?
Reducing land-use intensity quickly boosts invertebrate abundance, which, according to the authors, can be interpreted as a positive reaction of already locally existing species whose populations are benefiting from the reduced disturbance. As you can easily imagine, less frequent mowing kills fewer insect individuals. The species diversity, on the other hand, didn’t change after one year, which suggests that biodiversity recovery takes longer. Additionally, the species composition remained unchanged one year after the start of the extensification, which indicates a strong legacy of past intensive land use. Due to the lack of diversity data for the 2023 sampling, we don’t know if three years after the implementation of reduced land use, the diversity would have increased, or the species composition would have changed. That is for follow-up studies to find out.

Local land-use contexts and management details matter
The positive effects on abundance were smaller in frequently mown landscapes, likely because of the depletion of surrounding populations. Therefore, reducing land use in frequently mown grasslands may be less efficient, unless the area is connected to other unmown or larger habitats. The stronger effects observed in highly fertilized grasslands were likely due to productivity initially remaining high after the fertilization stopped, providing more plant resources for the invertebrates. Findings showing that cutting the grassland at a greater height and not mowing the entire area on the same day is less detrimental to insects demonstrate that insects require refuge areas. Therefore, if we want to promote insects in grassland restoration, we need to use spatially and temporally different mowing rhythms.

What are the take-home messages for conservation efforts?

The study highlights the need for long-term, sustained extensification for successful grassland restoration, whereby its effectiveness for invertebrate conservation varies across local contexts. Clearly, restoring grasslands can play a key role in counteracting insect declines, while a higher invertebrate abundance also supports insect-eating birds and key ecosystem functions. Nevertheless, restoration efforts must balance different biodiversity goals: While an intermediate mowing frequency can increase plant diversity, it can be detrimental for invertebrates. Maximizing restoration outcomes for both plants and insects therefore requires a landscape approach with different measures which also increase heterogeneity and habitat connectivity.

You want to learn more about the study and its findings? Then read the full article here: https://www.sciencedirect.com/science/article/pii/S1439179125000738?via%3Dihub

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A journey through the history of ecology

In the first half, participants were guided through the various research areas by tandem lectures given by the institute’s professors. Former senior professors and long-standing professors appeared alongside the current senior professors in their respective fields. Prof. Dr. Brigitte Urban, Head of the Landscape Change Working Group, and Prof. Dr. Vicky Temperton kicked off the journey through time with a look at what the history of ecology can tell us about the present and the future.

Brigitte Urban presented several research projects on ecological history. In view of the increasing human impact on our environment, it is particularly important to reconstruct former ecosystems in order to understand the current state and enable effective landscape management. While the past teaches us that settlement and human land use can cause long-term problems such as soil erosion in many places, there are also positive examples of natural resilience. The marshlands provide good news in this regard: research on the historical development of upland marshland vegetation reveals that they have a high degree of adaptability to purely climatic changes, even in modern times. However, pressure on upland marshlands is increasing due to human use and climate change, putting this flexibility to the test. If we go even further back in time, to the last interglacial period approximately 125,000 to 115,000 years ago, we encounter very large herbivores, known as megaherbivores. They may have played an important role in shaping the vegetation. What would our landscape look like today if megaherbivores still existed? Brigitte Urban is investigating.

Taking the history of ecology into your own hands

What happens to ecosystems when species are lost? And how does this affect ecosystem functions and services? Vicky Temperton addresses these and other questions in her research. Preserving and restoring biodiversity is not just about species diversity, but also about which plants play a role and what functions and interactions they have. Due to increasing biodiversity loss, it is becoming increasingly important to understand the development of plant communities in order to restore biodiversity. ‘Priority effects’ show that the developmental history of a community, through species that arrived first, influences not only species composition but also ecosystem functions. Vicky Temperton showed the audience that ecologists are not just spectators on a journey through time through the development of plant communities but can and perhaps even should change the history of plants themselves in order to promote biodiversity or certain functions. For instance, positive interactions between certain species groups could be used and the order in which plants arrive in a particular ecosystem could be changed.

Artificial intelligence to the rescue

Looking ahead to future research, each of the tandem presentations included an introduction to new research methods and projects in the respective fields. A glimpse into the future of ecology shows that machine learning with the help of AI can indeed lead to the desired breakthrough in biodiversity experiments. AI is therefore useful both as a measuring tool and for the interdisciplinary integration of ecological knowledge.

A plea for cooperation between science and practice  

At the end of the first tandem presentation, the big question arose as to how all this accumulated ecological knowledge can be integrated into society. Have you ever heard of real-world laboratories? In this format, stakeholders from science and practice work together to develop solutions to problems. The focus is on mutual learning in an experimental environment. For Vicky Temperton, real-world laboratories are important in socio-ecological research on the renaturation of degraded ecosystems. ‘When real-world laboratories are scaled up, they offer great potential for transformation,’ says the professor of ecosystem functions and services. And this transformation, with a balance between ecological and social perspectives, is absolutely necessary for the successful renaturation of ecosystems.

‘Insects are incredibly important for everything we do.’

The journey through time continued with Prof. Dr. Michael Staab, who is Head of the Department of Animal Ecology and Trophic Interactions. Representing Prof. Dr. Thorsten Assmann, Professor of Ecology with a focus on animal ecology, who was unable to attend, he provided insights into the great diversity and importance of insects and their ecosystem functions. The past also plays an important role in animal ecology, as Thorsten Assmann’s research on the significance of ice ages for today’s ecological composition shows. The beetle expert is also the only one who has documented the decline of ground beetles through biodiversity monitoring in the Lüneburg Heathland. The rapidly increasing extinction of species is a constant companion in animal ecology research and the basis for many research projects.

Among other things, Michael Staab is investigating how interactions between species give rise to relevant ecosystem functions. How do biodiversity and interactions change when the environment changes? Studies of trees in south-east China show that more species also mean more interactions. A decline in species can therefore have a significant impact on interactions between the remaining species – and not in a positive way. Another focus of Staab’s research is the influence of land use intensity on insect diversity. His research shows that where land use is particularly intensive, the landscape becomes homogeneous and the microclimate in ecosystems also loses its diversity. In a new project, drone imagery will be used to investigate how microclimatic conditions change as a result of different forms of land use, causing insects to lose their habitats. One consequence of insect loss: if insect diversity declines, the ecological balance is disrupted. To prevent this, less intensive use is required – for example, through extensive grazing and staggered mowing.

‘Species extinction is the loss of our Earth’s natural historical memory.’

‘Can we afford this?’ asked Prof. Dr. Werner Härdtle, Professor of Landscape Ecology and Nature Conservation. He completed the lecture tour together with Prof. Dr. Sylvia Haider, Head of the Vegetation Ecology and Biodiversity Research Working Group. The clear message from both of them was that species loss is not an option – plant diversity ensures ecosystem functions. Using impressive images, Werner Härdtle compared the burning of tropical rainforests with the fire at the Anna Amalia Library in Weimar 20 years ago, in which thousands of globally unique books were destroyed. This comparison illustrated the enormous loss of species caused by the destruction of the rainforests. Härdtle reported on decades of research in the subtropics of China, where 400,000 trees were planted to experimentally investigate the influence of species diversity. With shining eyes and infectious enthusiasm, the professor presented the results: A rich diversity of tree species can increase the productivity of forests by up to 100%. These effects also help when trees are under stress, for example due to climate change. Species that are sensitive to drought are better supported by biodiversity. However, such biodiversity effects take time, and we should give nature that time.

Sylvia Haider focused on the present and future of biodiversity research. She emphasised the role of functional biodiversity, i.e. the diversity of different functional characteristics. This type of biodiversity research also takes into account changing environmental conditions due to climate change, human-induced disturbances and the introduction of invasive species, and their influence on functional characteristics. Haider and her colleagues are part of a globally unique working group that measures the functional characteristics of trees between species, within species and also within individuals. The result: high functional diversity is associated with a high diversity of ecosystem functions. Surprisingly, a substantial proportion of the variability comes from the individuality of the trees.

New habitats at altitude

Finally, let us turn our attention to another level, namely mountains and the research into plant diversity along altitude gradients. How are ecosystems in vulnerable mountain regions changing, and what influence do non-native, introduced species have on this? During the question-and-answer session, the topic of species migration to higher altitudes as a result of climate change was raised. On the one hand, this creates new habitats, which can lead to the protection of species, according to Haider. On the other hand, existing interactions are also disrupted and species that were previously specialised in the mountains are being displaced by migrating species. Research is now needed to determine how this shift will affect biodiversity at altitude in the future.

‘Quo vadis ecology?’ – A panel discussion with a view to practical applications and the future

With the setting sun on the guests’ faces and questions about the future of ecological research in their minds, the panel discussion continued after a short break for refreshments. The panel consisted of Prof. Dr. Andreas Fichtner, Professor of Vegetation Ecology and Biodiversity Research, Dr. Heike Brenken, landscape planner at the Lüneburg Heath Nature Reserve Association, Prof. Dr. Vicky Temperton and Prof. Dr. Michael Staab. The first half of the discussion focused on the big question of how to put scientific findings into practice and successfully transform society towards sustainability.

‘We simply cannot continue like this; there are not three Earths!’

– emphasised Vicky Temperton. How can the results of real-world laboratories be widely implemented and practical partners be involved in the process? According to Temperton, it is not only the results that are important for scaling up such projects, but also the process itself. Cooperation between different actors builds trust, without which transformation is not possible. Heike Brenken speaks from her practical experience when she says that basic scientific research is important, but that help is also needed to implement the results on the ground. This is where administration and politics come into play. An article in the local newspaper or a presentation at a farm festival can also be important in increasing citizens’ understanding of nature conservation. In response to the appeal to the administration, a voice from the audience representing the Lower Nature Conservation Authority in Lüneburg spoke up. The participant assured the audience that the administration was also making efforts, but that they often encounter many restrictions. The “adjusting screw” therefore also lies with the people who can change the regulations for nature and species conservation. The students who are being trained at the university as ‘change agents’ could be a glimmer of hope, as they will later form the interface between practice and science with a broad thematic overview.

In the final stages of the journey through time, moderator Agnes Friedel concluded by drawing attention to the pressing ecological issues of the next 15 years against the backdrop of global change. Andreas Fichtner spoke of three important pillars for the future: ecosystem stability, adaptation to global change and a more respectful approach to our environment. However, the core message of research is often not understood in its implementation. Our values play a special role here. What do we find important? What motivates us? The understanding and awareness of the effects of global change on ecosystems, which ecologists experience in their research, must spread throughout society.

But what are the specific steps that can be taken to protect biodiversity?

– asked one participant, and perhaps some readers of this article as well. There is much that can and should be done to preserve biodiversity. Here are a few suggestions from the panel and the audience:

• Spreading awareness in society and politics that we cannot live without nature
• Changing land use, for example by consuming less meat
• Reward ecological services in the economy
• Making sectors such as agriculture and forestry more environmentally oriented and less production-oriented
• Generating motivation for environmental protection at an early age in school

Politicians bear much of the responsibility for this, but grassroots movements within society also have a role to play. The panel and the audience agreed: people must be passionate about protecting biodiversity!

Our journey through different eras and areas of research has shown that communication plays a central role in the protection of biodiversity and ecosystems – because only if we continue to exchange ideas and work together can we achieve this goal. With these closing words, Agnes Friedel bid farewell to the symposium participants as they headed into the evening. And with this thought, this article also bids farewell to its readers as they continue on their journey into a future that could not be more significant for the development of ecology.

Photos: ©Jennifer Fandrich / Leuphana

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Tree species and fungi – A special experimental design

This question was addressed by Tama Ray and her colleagues (2023), including Andreas Fichtner and Benjamin Delory from the Institute of Ecology at Leuphana University Lüneburg (Delory meanwhile: Utrecht University). For their study, they used data from the myDiv experiment. MyDiv is an experiment that falls under the functional biodiversity research described above. The experiment aims to better understand the relationship between above- and belowground interactions in tree species mixtures. This is based on the assumption that forest stands rich in tree species with different types of mycorrhiza function best. A mycorrhiza is a complex cohabitation between fungi and plants from which both benefit. The fungi are in contact with the fine roots of the plant and improve nutrient and water uptake for the plant and in return receive carbohydrates produced by the plant. There are many different types of mycorrhiza, which can be roughly categorised as arbuscular mycorrhiza (AM) and ectomycorrhiza (EM). Trees at temperate latitudes can be associated with either AM or EM or with both types of mycorrhiza. AM and EM function differently and have different specialisations.

In the MyDiv experiment, both the influence of aboveground and belowground diversity on productivity was analysed together. This means that there were two diversity variables: Firstly, the number of tree species (along the gradient: Monoculture, two tree species mixed, and four tree species mixed). Secondly, the types of mycorrhiza (AM, EM or mixed AM and EM). The trees were planted in 2015 near Bad Lauchstädt in Saxony-Anhalt, Germany.

What did the scientists expect?

Ray and colleagues have hypothesised that the greater diversity of tree species aboveground results in a more complex structure of the forest, i.e. leads to an increase in structural complexity. Structural complexity characterises the differing distribution of tree biomass in the three-dimensional space: different tree species have different tree heights and form differently structured crowns and thus use the space in the canopy more diversely than just one tree species would. This could allow the trees to utilise the available light more efficiently. As all plants need light for photosynthesis, in addition to water and nutrients, such more efficient utilisation of light could result in increased photosynthetic performance and thus increased growth. The assumption was similar for a higher diversity of mycorrhiza types: Due to the different specialisation of the various types, the scientists expected that the belowground resource use of nutrients and water is more efficient in stands with different mycorrhiza types and thus also contributes to increased productivity.

How do you measure the complexity of a forest structure?

Not only the experimental setup but also the measurement method in this experiment is special. Conventional measurement methods analyse structural complexity in two dimensions. In this experiment, however, the structural complexity was recorded three-dimensionally using terrestrial laser scanning, and a structural complexity index (SSCI) was created from this. This means that the specific distribution of leaves, branches, and trunks of the trees in space was recorded by a laser and translated into a numerical value. Productivity was measured annually based on the trunk diameter and tree height of each tree.

Surprising results

The scientists discovered several things:

1. Interestingly, contrary to expectations, the diversity of mycorrhizal types did not influence the productivity of the young forest. The scientists suspect that this effect may only play a role in older forests than the young forest of the project, as other studies have observed such effects in older forests. 
2. With increasing tree species diversity, structural complexity increases.
3. With this increasing structural complexity, productivity increases. In other words, the more complex the structures of the tree stands, the better the forests grow.

In order to test the assumed effect of increased light utilisation, the scientists measured the light incidence on the forest floor. They found that the less light reaches the forest floor, i.e. the more light was previously captured by the tree canopy, the stronger the correlation between structural complexity and productivity. Ray and his colleagues have therefore concluded that increasing the structural complexity of the canopy allows the forest to grow better because the available light is then utilised more efficiently, meaning that more light is available for photosynthesis and thus for growth. The increasing diversity of tree species therefore has an indirect effect on the growth of the forest because it makes the structure of the forest more complex, which in turn allows the forest to grow better (see overview). In the experiment, forests with a more complex structure grew almost twice as fast as forests with a less complex structure.

Miracle tree species or team effect?

In the next step, the scientists wanted to find out whether the observed increase in productivity was due to a specific tree species or whether it was caused by the mixing effect. To this end, they calculated the so-called “overyielding”. This describes the increased growth of a tree species that only occurs when it is mixed with other tree species compared to a monoculture. So, if a beech in monoculture would grow 5 m³ per tree per year, but in a mixture with oaks, for example, it would grow 8 m³ per year, then this additional growth of 3 m³ per year would describe the overyielding. The overyielding therefore describes the net biodiversity effect of the mixture of tree species on the productivity of the individual tree species (which grows in this mixture). This effect can be mathematically divided into the species identity effect and complementarity effects. The former would be an effect for which a particular tree species is responsible, the latter an effect caused by the mixture of tree species. This can be compared to a football team: Does a team win because it has a particular football player on the team who plays much better than the others, or does it win because the team as a whole plays so well together? The effects in this experiment could largely be explained by the team effect, i.e. they are mainly complementarity effects.

Light-loving and shade-tolerant complement each other well

The scientists found that structural complexity explains half of the variation in productivity and that almost two-thirds of this can be attributed to this mixing effect of tree species alone. This strong effect of the mixture of tree species itself could be traced back by the scientists mathematically. They found that the effect can be explained most strongly by different shade tolerances of trees. Birches, for example, do not tolerate shade well, but beeches do and can therefore thrive under the fast-growing birches. Together, this gives them more space in which they can grow optimally and therefore more complexly. Thus, the more diverse the shade tolerances of trees in a forest are, the better and more complex the space can be utilised, which means more light can be captured and thus more light is available for photosynthesis, so the forest grows better (see overview). In addition, taxonomic diversity (i.e. the different ancestral histories of trees) also influences this stronger growth in mixed tree species. The scientists have not yet been able to explain exactly why this is the case, but they believe it could be due to the different shapes and branching patterns of the tree crowns of the various tree species.

How can these findings be used?  – Climate change and drones

These results provide valuable implications for practice, including the restoration of forests: For example, tree stands should be designed in such a way that they contain several tree species that have different light requirements. This would allow the forests to grow as quickly as possible and store larger amounts of carbon aboveground, which is particularly relevant in view of climate change. In addition, the structural complexity could be used as a proxy for productivity in the future based on the results. In the course of new satellite-based methods and drone applications, the structural complexity and thus productivity of a forest could be assessed relatively quickly and over a large area, thus, for instance, improving the predictive power of carbon models.

If you want to delve deeper into the topic, you can find the paper by Ray and colleagues here: Ray, T., Delory, B. M., Beugnon, R., Bruelheide, H., Cesarz, S., Eisenhauer, N., Ferlian, O., Quosh, J., von Oheimb, G., & Fichtner, A. (2023). Tree diversity increases productivity through enhancing structural complexity across mycorrhizal types. Science Advances, 9(40), eadi2362. https://doi.org/10.1126/sciadv.adi2362

Cover picture: Structurally rich beech forest in Sweden (Photo: Andreas Fichtner).