Entomologist Kateřina Sam on the disappearance of birds and insects and their crucial role in the eco-system
Entomologist Kateřina Sam is on the 2023 Forbes list of top Czech female scientists. She has been working on an experimental study aimed at mapping the interdependence of birds and insects and how their disappearance may affect the landscape and in turn humankind in different parts of the world. I recently had the chance to speak to her about her work.
“The project is important because we previously observed that insectivorous birds are missing from some of the tropical forests. When the forests are disturbed the abundance and diversity of these birds goes quickly down. So we wanted to study what would happen if the birds were to disappear completely. We built cages around selected trees, so as to simulate their disappearance.”
Where did you do this?
“We did this at several study sites across the globe –in Japan, Germany, China, in Papua New Guinea and at two study sites in Australia. However, some of the results are only just being analyzed now. We recently published the results of the study in Papua New Guinea. There, the situation was quite specific because we worked around Mount Wilhelm which is the highest mountain of Papua New Guinea and we worked at study sites which were 3,000 meters above sea level and as low as 200 metres above sea level. So a 30 km long elevation gradient.”
And were your findings a particular cause for concern – what did you find?
“In Papua New Guinea we found that the abundance of arthropods increased by dozens of percent. Typically we have around 20 arthropods per square meter of foliage, but when we excluded the predators their numbers doubled, sometimes even tripled, which is a problem for the plants because tropical plants are really sensitive to herbivory damage and when the arthropod communities increased they were causing much higher damage to the trees. The herbivory damage increased by roughly 10 to 20 percent on average. This damage might be critical for small saplings –they could die in the next season or the course of several seasons. That affects the restoration of forests. Because when the forest is selectively logged, the birds disappear, because they don’t like partially logged forests. These areas get lighter and warmer and the birds leave. When that happens the number of arthropods increases and the number of insects increases and they cause more damage to the small saplings. So the restoration of the forest does not happen naturally or it is lower than what we would like to see.”
Here in Europe we keep hearing about the fact that the insect population is disappearing at an alarming rate –are you more worried about the number of birds dwindling or insects dwindling?
“In Europe the situation is different, because insects are disappearing much faster that birds –in tropical forests we have the problem that forests are being logged and that hurts the birds. In temperate regions typically we have the problem than nature is being forested and so we are losing insects tied to open habitats. So the situation is radically different and in the temperate regions I am very worried about the disappearance of insects which in turn might lead to the suffering of birds.”
When you are conducting these experiments what are the practical impacts? Are governments listening and taking action or is it simply at the stage of being an experiment?
“So far, it is at the stage of being an experiment. We are trying to talk to the locals –villagers and landowners – in Papua New Guinea, now that we have the results published. But later on we hope that the results of our experiment will have practical use in nature protection.”
What kind of steps might be taken?
“Measures could be taken to maintain an abundance of insectivorous birds in tropical forests and we might be able to calculate what would be the threat and how much plant biomass we would lose if we lose the birds. So the results can be used in agricultural ecosystems where farmers are already using some ways how to increase the abundance of insectivorous birds to help keep their crops protected against pest insects.”
Is the loss of rain forests damaging birds or insects more?
“It is damaging primarily birds. Because a tropical forest is a very stable habitat. It is dark, humid and relatively cool in the forest interior and the birds are physically adapted to this environment. Their eyes are more adjusted to the dark conditions of the tropical forest. And as soon as logging starts and the forest opens –its edges get hotter and lighter – the insectivorous birds have a hard time. They have trouble hunting and generally surviving in this hotter environment.”
As an entomologist –are you concerned about the damage done to the Planet? Because some scientists feel we have already crossed the red line…are we seeing a domino effect?
“I don’t think we have crossed the red line yet, but the damages we are causing are pretty alarming. I think we have lost about 10 percent of the diversity of arthropod insects so far, which is very high. Because the arthropods are very difficult to count, we don’t know how many we have. It is difficult to judge how many of them we have killed already. There are some signs that we have damaged a great many of them already and that their populations are decreasing, but it is very difficult to quantify and say whether we are approaching the red line or not yet.”
What is the situation like in Europe and the Czech Republic in particular? Because some say as many as 75 percent of insects have disappeared.
“I would be cautious with these numbers. Insects are definitely disappearing, but because we do not have a standardized, reliable way how to count their numbers, we cannot really say that so many insects have disappeared. Yes, there are signs that arthropod communities are disappearing. On the other hand, there are insects that are doing much better. Climate change is generally leading to higher temperatures and some insects have more breeding cycles during the year as a result. So there are some insects that are doing better and some insects that are reacting negatively to the land-use changes and the use of pesticides in Nature.”
That will change the biotope here.
“Definitely. These changes are happening because every arthropod has its own role in the eco-system so some of them, which function as pests, might be increasing their abundances and others, which are pollinators, could be decreasing their abundancies.”
The authorities are now reforesting trees and often picking different tree breeds to prevent the spread of bark-beetle infestation. Could reforesting be a problem for insects?
“No, I think that if the reforestation is being undertaken correctly, with the correct plant species, then it could be helpful.”
Insects are seen as a future source of food for the Planet. Is that realistic and would their artificial breeding at farms interfere with their socio-behavioral patterns and maybe affect the balance of the eco-system?
“I don’t see this as something that would happen in the near future. Insect protein can be used as a part of certain dietary needs, but I don’t think it will replace meat fully. Of course, the breeding of insects is less energy-demanding, more economical but still there are not so many people willing to eat insects and introduce them in their daily menu yet.”
You have worked in countries around the world. Do you have a pet project – a goal that you have set your sights on in your given field of activity?
“Actually, what we found in our recent research is the quite important role of spiders. These are not insects, these are arthropods, which typically took over when the big predators disappeared. And we are also running several experiments in agricultural land that show that when the insectivorous birds are gone, because they don’t like agricultural land, the spiders work pretty well and provided some of the eco-services which the birds did before. So now I am fully focusing on the spiders and their interactions with birds and maybe some useful practical tips on how to enhance the populations of spiders in the agricultural land so as to help increase crop production.”
And are you happy with the way that government and local authorities are responding to the results of your research – and research of others in the field of environmental protection – or do you feel that more should be done?
“I feel quite positive in places like Papua New Guinea where all the land is owned by the locals and when I work there they like to help. They see what I do, they really listen and they try to make changes because this is their own land, their own future. It is more difficult to work and disseminate the results of our work in countries like the Czech Republic where the government doesn’t listen too much.”
