Interview: Gaby Allheilig
When discussing the question of how Switzerland’s biodiversity is doing, people cite a variety of figures. Some refer to habitat sizes, others to the Red List of endangered species, and so on. So how is biodiversity measured?
First, there’s the question of what to measure. The examples you mention both provide good indications of the state of biodiversity. But they each cover only a certain part of biodiversity. Results may differ depending on what you look at. Nonetheless, there’s consensus on what biodiversity is comprised of, at least in a broad sense: ecosystems or habitats, species, and genetic diversity.
Why only in a broad sense?
Because you can differentiate even further. In terms of species diversity, for example, you can check how many species are actually present, how many individuals of a species there are, and in which locations or habitats they occur or no longer occur.
You can also analyse how much diversity there is within a species – that’s an aspect of genetic diversity. Species with a large gene pool generally have a greater chance of survival, for example if environmental conditions change. So if you want to describe the state of biodiversity, you should map as many of these aspects as possible.
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“When looking at ecosystems, you have to take into account both their size and their condition”
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So, one of the aspects that should be considered is the overall area of the various habitats. Is there any particular focus in this regard?
When assessing biodiversity, it’s particularly important to look at habitats that are ecologically valuable. In Switzerland, these are primarily nature conservation areas, such as moors. If these decline, biodiversity everywhere is in trouble. But not all moors are the same. A moor that begins to dry out is still a moor – but it’s no longer in a good condition. That’s why we need to look at two factors when assessing habitats or ecosystems: their size and their condition.
And how do you measure that?
When it comes to measuring species diversity, monitoring based on systematic data collection is still the most common method. The most comprehensive such programme in Switzerland, “Biodiversity Monitoring Switzerland”, has established a sampling grid comprising several nationwide monitoring networks. These consist of specific plots in which experts record the species present and their respective numbers at regular intervals. It’s quite a time-consuming method, but it allows us to make representative statements about changes in species diversity. The longer the data series collected, the more robust our understanding of these trends becomes.
Switzerland also has other ways of counting biodiversity. Some data and information centres, such as InfoFlora, allow anyone to contribute to biodiversity surveys by submitting observations. These data are very valuable, but they require careful interpretation, as collection is not always systematic. For example, there are more data for areas frequented by greater numbers of people.
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“There are still major gaps in the data”
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All these methods are based on counts. What about surveys using satellite data, airplanes, drones, and so on?
Remote sensing can help to assess habitats. Used in combination with modelling, it can help to assess species diversity. For example, if you’ve recorded the species composition of a certain forest on site, you can take aerial photographs of a similarly composed forest elsewhere and derive the probability of certain species occurring.
In addition to remote sensing, there are now other methods for monitoring biodiversity. You can use environmental DNA or eDNA, for example, to identify the animals in a certain place based on the traces they leave. If you find fish scales in a body of water, or patches of fur on the ground, genetic analysis can tell us what animal it is. In other words, you search for traces instead of counting species or individuals.
Switzerland already has several programmes in place to monitor different aspects of biodiversity and assess its status. Why do we need more data and measurement series?
There are still gaps – for example in relation to insects or soil organisms. And especially for genetic diversity. As far as I know, there are no systematic surveys on the genetic diversity of wild species in Switzerland. New methods and technologies can be helpful here.
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“If you simplify, you mustn’t change the basic message”
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Measurements and data don’t protect biodiversity. What’s the ultimate aim of the monitoring programmes?
First, it’s about determining whether there’s a need for action and what needs to be done. The Red List is one such instrument. It provides information on which species are endangered and need to be protected. The second objective is to monitor effectiveness. This involves checking whether the conservation measures taken are having the right effect. For example: Is it useful that we’ve placed our moors and dry meadows under protection? Or is biodiversity still declining there – and if so, why?
Nearly every monitoring programme is accompanied by an extensive report. Why aren’t these findings communicated to the public in more suitable ways?
It’s true that in contrast to climate change, public awareness of biodiversity is probably still in its infancy. But then, there’s no one simple catchphrase for biodiversity as in “greenhouse gases lead to global warming”. This is because the various aspects and interrelationships involved in biodiversity are even more complex than those involved in climate. And this brings us to the challenge of science communication. It’s important to simplify, so that the findings are understandable – but you mustn’t change the basic message. If that happens, you have to pull the brake.
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“The question is how to aggregate the different monitoring programmes”
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At the Swiss Biodiversity Forum, you’re working on a project to develop a kind of overall index of biodiversity in Switzerland. The aim is to reduce the wealth of data to an easily understandable denominator. Is this an attempt at squaring the circle?
A pilot project revealed a large discrepancy between simplification and scientific statements, and a range of opinions. Initially we aimed to evaluate the feasibility of implementing in Switzerland an international proposal by scientists for a “multidimensional biodiversity index”. This proposed index looks not only at the state of biodiversity, but also at how biodiversity benefits humans. The latter aspect was dropped in Switzerland after the pilot project. We’re now working to establish a comprehensive national index on the state of biodiversity and how it’s changing.
And how is this going?
The big question here is to what extent we can aggregate the various biodiversity monitoring programmes. For example, is it sensible and possible to link the diversity of species in water bodies with the diversity of species in terrestrial habitats? Because if you want to calculate or simplify an index, everything has to be comparable...
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“Diversity is the core element of resilience”
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... in order to provide a number that summarizes it all?
For biodiversity, it wouldn’t make sense to use just one number, as we do for the CO2 balance, for example. Besides, if we simplify, we also have to explain what the simplified finding means and how it should be interpreted. This raises questions: At what point is a development positive or negative? That’s easy to answer if we use criteria like “endangered species”. But we need to go further when we’re talking about diversity: Where do we draw the line when we say something is good or bad? And to what point in the past do we compare the current situation? All this is important in assessing the development of biodiversity. Research still has some hurdles to overcome here. How much of this policymakers will want to take on board is another matter.
Finally, a personal question: What does biodiversity mean to you?
I think that diversity is the core element of resilience and capacity to adapt. Each loss of a species or habitat weakens the resilience of the whole system a little more. And ultimately, everything depends on this system – whether it’s our food supply, disaster prevention, or recreational space.
