Sustainability

A slightly untidier Zuidas

Urban ecologist Bas Reussien aims to increase the biodiversity of Zuidas by means of varied and native plants. ‘When the entire food chain is in balance, you can prevent infestations of mosquitoes or oak processionary moths.’

‘Nature in the city is always a controversial issue. The vision that urban designers have for a street is often at odds with what ecologists would like to see. A row of trees of the same type, as in Minervalaan, may look attractive, but is less valuable for nature. This is why ecologists prefer more variety. Slightly more untidiness, even in Zuidas. That’s how you ensure there’s always something in bloom and insects always have something to eat. Our aim is to try this out on land that will ultimately be built on, but still has enough room for vegetation until that time.’

Native

‘In Vijfhoek park, there are various types of trees, almost all of them native. Native trees are important, because Dutch animal species are completely adapted to them. Scientific studies show that native trees attract hundreds of species of insects, whereas a tree taken from Asia or North America will have only a few species on it. Our focus is on native animal species. Exotics, like the rose-ringed parakeet, are better deterred, because they compete with native species. They’re taking their place and eating the same things. So, we’re not taking any measures to conserve rose-ringed parakeets, although I personally always enjoy seeing them.’

Spring, row of trees in Vijfhoek park
Spring, row of trees in Vijfhoek park Photo: Jan Vonk

Balanced food chain

‘Biodiversity is about ensuring that the entire food chain is in balance. This preserves the power of the ecosystem and helps prevent excessive numbers or infestations. Take mosquitoes, for example. If they have no natural enemies, they can quickly reproduce uncontrollably. If there are sufficient numbers of birds and bats to eat them, you can prevent these excesses. In the past, we often used poisons and other chemical products. But nature has its own ways of dealing with these things, which we can take advantage of. Another example is the oak processionary moth and its caterpillar. It’s eaten by various birds, beetles, parasitic wasps and ladybirds. The greater the biodiversity, the more natural predators there are. And if the local council ensures there are enough plants and nesting opportunities, you can keep the caterpillars in check. Then there’s water quality. You can ensure this stays high by making the right choices on the banks of the canals and on the canal bed, with a lot of varied planting. Organic substances that have dissolved in the water feed algae. Algae are eaten by water fleas, which are in turn eaten by fish and by birds. If all of these can be present to a sufficient extent, the chain remains in balance.’Part of a bigger picture

‘The great thing about biodiversity is that it’s also part of a much bigger picture. A lot of vegetation also prevents heat stress and helps to capture excessive rainfall. Research shows that a lot of greenery enhances quality-of-life and reduces stress. If you step out of your house and hear a bird singing, it makes you happier. Whatever your perspective on policy, the advice for designers is effectively the same. The water- retardant green strip in Prinses Irenestraat is a good example of this. If you make the right choices, you can incorporate all of this in a design.’

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