Biodiversity essential for the smart city

Systematic charting paves the way for conservation work

Dragonflies lay their eggs in and around bodies of water. The larvae live in water, while the adult dragonflies fly. To be able to follow their development for a longer period of time, Göran Sahlén usually works with larvae:

“To create a picture of the larval habitat I study the bodies of water where they live. The type of water is affected by numerous factors, each of which changes the properties of the water and affects how rich in species a body of water has the potential to be. This may include the availability of food, the vegetation and its depth. Temperature is also a significant factor. Dragonflies are poikilothermic and grow with warmth. Therefore, they benefit from warm temperatures. The heat accelerates their growth, which gives them an advantage. In the insect world, it’s very useful to get big quickly.”

Dragonflies can serve as a measure of the richness of species in a habitat as they are the predators that are highest in the food chain of lakes – with the exception of fish – and a large number of dragonflies indicate a species-rich body of water. By systematically identifying not only how many individuals of a particular species live in a location, but also how many different species and which of the various species are gathered in and around a specific watercourse, Göran Sahlén draws conclusions about the overall species-richness of the water.

“All species that are below the dragonflies in the food chain, such as herbivores and various decomposer organisms, are regulated by the number of dragonflies. The presence of a large number of dragonflies indicates that the water is rich in food. From this we can conclude that the lake as a whole is rich in diversity. If instead the number of dragonflies is low, we can suspect that the lake is species-poor. In this way we can apply what we learn from the efforts to systematically identify the presence of dragonflies to other aquatic organisms, and from that we can work with nature conservation.”

Swedish and Brazilian dragonflies raise the same questions

Dragonflies are a tropical group of organisms that have developed adaptations so as to also be able to live on northern latitudes. Even though we find dragonflies in Swedish waters, the great diversity of species is found on more southern latitudes. Therefore, Göran Sahlén performs a large part of his research activities in Brazil, in collaboration with Professor Eduardo Périco and his research team at Universidade do Vale do Taquari (UNIVATES).

“The research questions are identical, whether I study Swedish or Brazilian dragonflies. In Brazil we work in two different environments: partly in a type of rainforest called Atlantic Forest and partly on the large grasslands, for example Pampas”, Göran Sahlén says.

The Atlantic Forest, which extends along the Atlantic coast of Brazil, is one of the world’s richest ecosystems, but today only a few percent of it remains. The rest has been deforested to make room for grazing animals or for the cultivation of crops, for instance sugar canes.

“When imagining a rainforest, we usually think about the tropics, where it rains daily and where there is a mass of flowering trees and other plants, but that is not representative for the Atlantic Forest. Here the vegetation is instead mixed with conifers and there are distinct seasons. Summers are dry and winters are cold. It’s very different from how we often imagine the rainforest”, says Göran Sahlén, comparing the Atlantic Forest to the more famous Amazon rainforest:

“The biodiversity of the Amazon and how it is threatened by fires and deforestation is common knowledge, but the Atlantic Forest is not as well known, despite the fact that it holds many more species than the Amazon.”

Changed biotopes and water shortage threatens biodiversity

Biodiversity on the grasslands is also under threat. While the Atlantic Forest is being deforested, trees are being planted on the plains. With the goal of being able to harvest the planted forest as quickly as possible and thus attain as much yield as possible, fast-growing tree varieties, such as eucalyptus, are chosen.

“Instead of letting the grass plains be just plains, we see that crops, often trees, are planted on them. By doing so an open field biotope is transformed into a forest, which is harmful to biodiversity. Species – both plants and animals – that need a lot of sun cannot cope with such changes. A species can be either a generalist species or a specialist species. If one is a generalist, it can do most things. It adapts. But if one is a specialist, it is dependent on a specific factor and if that changes things go awry. Then the possibility of surviving is nil. But of course, there’s a whole range of species in between the two extremes. Some species are able to adapt and survive just fine while others do less well and disappear entirely”, explains Göran Sahlén and continues:

“Access to freshwater is also a limiting resource, for dragonflies and for all life, including humans. In recent summers we have experienced water shortages in many places, even in Sweden where we ordinarily have good access to water. This concerns the groundwater – the part of the water’s natural cycle that takes place underground. Surface water – the water found on the Earth’s surface in the form of lakes, streams, wetlands and seas – we haven’t seen a shortage of, and therefore the drought has not negatively affected the dragonflies. Elsewhere in the world, things look significantly different. Down by the Mediterranean Sea, for example, much of the surface water is used for irrigation of crops, making it difficult for aquatic organisms to survive. We must learn to use water in a smarter way, so that the environment is not harmed by the development of society.”