How can networks help us to better understand islands? - Jens Olesen in interview

Interview by Marta Daniela Santos

Networks surround us in every aspect of our lives. Social networks, transportation networks, power grids...there are innumerous examples. And of course, networks are also an invaluable tool in Biology.

Jens Olesen (Aarhus University, Denmark) is interested in looking at islands in their entire complexity by studying the networks of interactions between the species that live on them. What can we learn with this approach, that we cannot learn by studying individual species? Which predictions can be made?

In this interview Jens Olesen talks not only about this interdisciplinary research area, but also about interesting patterns he found while studying species interactions in the Galapagos Islands, and the (exhausting) experience of organizing an International Biology Olympiad.


Right now we are using a network to have this interview - the Internet [the interview was conducted via Skype]. But networks are everywhere, right? Can you give us a more concrete idea of the different kinds of networks that are present in our lives?

I think social networks were the first kind of networks to be studied. When I give public lectures I often use them as a reference, because that makes it much easier to understand others that might be more abstract. On social networks you have interactions of all kinds - friendship, family, colleagues, political parties, and so on - and you can identify the links in many different ways.

In the 1950s and 1960s sociologists were already studying social networks, but only small ones. Now we have big data, for example mobile phone networks and Facebook, and many scientists are now using huge social networks. I take these concepts and software and bring it into Ecology.

There is that popular saying that any two randomly chosen people are connected on average by 6 degrees of separation. Does it really work that way?

Yes...more or less. [laughs] It’s the average. Of course there are longer and shorter paths between people, and it's an old expression too. In the 1960s there was an American sociologist, Stanley Milgram, who was asking that question - "how close are we to each other?". He did an experiment with a chain letter, and it turned out that the answer was 5.5 in US at that time. But now many people would say that the 6 degrees of separation is global.

Let's imagine, for example, my distance to another random person in the world. I know somebody who knows more people than I know, and that person knows more people than that go to the core of the social network, where you have people with a lot of connections, and then you go to the periphery again. That's the way it is always organized: many people with few links, and a few people with many links. It's the heterogeneity in it that makes the distance so short.


Nowadays we are more and more connected, so maybe the 6 degrees of separation figure is shrinking?

It is difficult to know, but I think it will be shrinking. For example: you see kids playing on the computer and they don't care if they are playing with somebody in Coimbra or in New York, because for them geographic distance does not exist anymore. We are on a transition: of course we know our neighbors and our friends and they live close to us, but we also know somebody far away. It's a transition from an old and maybe medieval situation, when you only knew somebody in your close neighborhood, and the future in which you will completely ignore geography.

Since we are increasingly more connected online, do you think that will affect our abilities to socialize with people? Will that have consequences, of us being less able to empathize?

Sure, of course. That’s a debate in this country, that kids are losing their social emphathy. But it's difficult to know, because you can also expect that people become more flexible and more able to cope with many kinds of links, for example. But I don't know the sociology literature, I don't know if that is the trend.

So it is an open question.

Yes, to me at least. Maybe there is somebody out there in the network that knows more. [laughs]

So, we have networks everywhere...including islands. Your research focuses on the networks of interactions between species on islands. What can we learn more about an island from this abstract perspective?

When I do a network study on an island, I am interested in the entire complexity of the island. Traditionally on islands, and also on mainland, people have been studying single species or a couple of related species and how they behave. Then, of course, the more data and software you get the more you're able to study more and more complex systems. And I think that one first step is to study islands. Because they are simpler systems - of course, compared to mainland -, they have fewer species, and it's possible to collect the data in the field. That means you can study the complete entity - island ecosystem or island network. You look at the big animals, plants, insects and so forth, and you can also include various kinds of links, such as predation, mutualistic links between species and so on.

By using the appropriate software you can also start to look at emergent properties, properties you could not anticipate the character of if you just studied species A, B and C. Because there is a kind of self-organization in the system: you start having hundreds and hundreds of species and you cannot take a single species approach, you have to pull lots of data together and use network software. Then you can study if the network is more or less stable, if it is resistant against invasion, or how fast will it recover if a hurricane strikes the island or something like that. You can start looking at it as an entity, and I think that is what is really fascinating.

So species extinction, or the emergence of new species, creates new links. Will those links generate cascades or something on that network?

Yes, it does.

And this approach allows you to study it in a more global way.

Yes. Of course you can do computer simulations. You can have this interplay between adding more and more data, from more and more islands, and then you can start killing species - on the computer! [laughs] - or adding species, and see what happens to the properties of the entire network. All the time we have to make a reference to the real work, of course, but still, we can make the models more and more realistic.

But it's true when you say that we see these cascades, and it is very difficult sometimes to predict what is going to happen. For example: many islands have lost top predators, maybe instead they got human introduced predators. That affects some small animals, and that affects smaller and smaller animals and finally the plants - this is called a trophic cascade. It is really fascinating, but extremely difficult to anticipate what the outcome is.

That's very interesting. Also, with some of your colleagues you have invested a lot of time in studying species interactions in the Galapagos Islands. Did you find any interesting pattern? Do you want to share any interesting story about this emblematic archipelago?

Of course! First and foremost, it is true that they are very famous, and many scientists want to do work there. But to some extent they are, more or less, like other islands. One of the reasons to do the study there is that most of the islands are more or less outside, or have not had very much human influence. You have therefore islands that are inhabited by humans, and then there are the other islands which have either never been inhabited or are now restoring the damage caused by humans. This makes it possible to look at islands in a much more pristine state, and from that point of view it is really interesting.

What we see there is that most species live on an edge of starvation. The species there are able to survive because they are very flexible in their ecology, they are very plastic. You can take an insect-eating bird that may suffer from lack of food and then, during some months in the year, they start eating seeds or visit flowers for nectar, or they even go along the beach and take small marine animals. So these animals survive because they are extremely flexible in their ecology, and that's surprising!

Scientists or ecologists, we think we know what we are going to see, and then we are only looking for that. And it becomes more difficult the older you get, because you think "I've seen it before". But when you go there and you try to be completely open-minded, then you suddenly see these surprising things.

There is always more work to be done there.

Oh, yes. That is for science in general, it is an expanding universe. One answer gives three new questions, and you get new is never-ending.

In the case of islands, it is difficult today to find pristine islands around the world. And by using network analysis you can look at the robustness and you can also see where are the weak points in the network where an invader could get into.

It is also important to study these networks from a restoration point of view, because that is also what is going on on the Galapagos. For example, last time I was there they had eradicated rats on a small island, and then of course you have to see what is happening afterwards. It's not always beneficial, even in the first decades, maybe because some other native species have benefited from invadors. It could be that rats were eaten by native Galapagos hawks, and when you remove the rats the hawks have to find other food items. You get a reshuffling of the native networks after you remove the alien elements, and that again makes it very difficult to predict the outcome.

You also said [on the plenary talk at the Island Biology 2016 congress] that you want to bring the sea back to island biology. What does this mean?

Well, it's been a kind of common wisdom that islands in the big oceans are isolated. And of course they are for land animals and land plants. But islands are not isolated, not in the sense that they are connected to the surrounding sea, and if the sea is very productive on the plankton and the fish and so on, it makes it possible for sea birds to have huge colonies on these islands. And sea birds bring organic matter from the sea all the time. That input of nutrients is extremely important on many islands. So, it is this interplay between the land and the sea that has to be included in island biology models.

It will probably lead to new predictions.

Yes, I'm sure it will. For example: in the Galapagos you have these El Niño years in which the sea temperature increases and the sea becomes more or less dead, and then the mammals or birds that live on Galapagos and get the food from the sea stop reproducing, and many die. But in the same years you have lots of rain, and the land flora and fauna flourish.

Then, in between the El Niño years, it's the marine life that is flourishing, and the finches and all the other birds at the Galapagos stop reproducing at all. So it switches between years, it goes back and forth all the time. And this fluctuation between states is also found for many other islands around the world.

That’s really interesting.

Now I would like to focus on some other recent projects of yours as well. You were involved in the organization of the 26th International Biology Olympiad: how was this experience? Which challenges did you find?

Oh, it was exhausting! [laughs] It took us several years to prepare. We went to three Olympiads the years before to see how it was organized. But let's start with the beginning.

The Biology Olympiad is for highschool biology students, so they are in between 17 and 19 years old. In Denmark last year we had 61 countries; from each country come four students and their teachers. So we have around 250 students, and probably 500 to 700 teachers. My job was to make the questions: they have two theoretical exams and four practical ones in different fields - animal physiology, plant physiology, microbiology, biotechnology, and so on.

In the theoretical exams I made one hundred questions. There's an introduction and then they have multiple true-false statements, and this has to be based on recent scientific research. I find a paper, make some short introduction, four statements, and the students will have to say if they are true or false. Then, when the guests come and the Olympiad begins, we place all the teachers in a big room in the day before the exam and they have to translate my English questions to their own language. They are not allowed to communicate with the students: they [the students] stay in another hotel, and we confiscate all their phones. Very secret! [laughs] Then they upload the questions in their own language, and we begin the exams.


The International Biology Olympiad 2015 in Aarhus, Denmark.

The practical exam in animal physiology.


It was a lot of work!

Yeah. It takes a long time, and it’s difficult to agree about the questions and the answers. There is a lot of negotiation in the teacher's room, with all these countries, because of course, they think differently when you have 61 countries. But it is a wonderful experience. You get a lot of nice friends from all countries, and you start seeing how different humans from different cultures look at Biology. That is really interesting.

You were saying you had to confiscate the students' phones...The kids at this age are increasingly more online: how do you see the challenges of communicating science, and your work in particular, for this new generation?

When we asked the students why they were interested in Biology, for example, we got lots of different reasons. I think that basically from European countries students are very much motivated by their personal interests, and they get this interest from very different sources. It could be the school, it could be parents, friends...

But if you go to other continents, like for example Asia - there were a lot of Asian countries present - they also have the motivation that if they score very high at the Olympiads, they get free university studies. They have this social mobility carrot in front of them. And that is not the case, I think, for any European student. Maybe in Europe we would take a competition like this a little bit relaxed, but for the Asian students it is extremely serious. It's all about their entire future. So we get complaints from these countries if they feel that they have been scored incorrectly, which we have to take care of.

And there's also the fact that many countries are suspicious that other countries are cheating. Because you can imagine, it's very difficult for us to control all the translations, and there have been cases of cheating over the years. We check it out, of course, but for a small sample, as we don't master all these languages.

Overall there can be very different reasons for the students motivation to study Biology; I think it is difficult to generalize.

I hadn't thought about that perspective. The backstage of organizing such an event can have different details that we don't know about.

To summarize our interview: what are the challenges you see for the future of your own research field?

For me, I continue working with islands. Again because they are simple systems, and they could be models for continental systems. I am also interested in Islands because they constitute this small portion of land area in the world and at the same time they have such a high proportion of the biodiversity. And they are the systems in most danger, of course.

Also, I want to understand the dynamic of the complexity on islands. For example: I was talking about how you can move quickly from one state to another, from El Niño years to La Niña years [La Niña and El Niño are natural phenomena of rich marine life/poor land life and poor marine life/rich land life, respectively], and how you can have a native predator suddenly disappears that causes these cascades into the system. This is part of a new theory that came out 15 to 20 years ago: critical transition theory, where you approach tipping points and then suddenly go into another state. I want to incorporate that theory in my work with island biology, because only very recently I understood that these things are more connected than I previously thought.


Jens Olesen was plenary speaker of the international congress Island Biology 2016, organized by the Azorean Biodiversity Group - cE3c.