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In the spotlight: Hans de Kroon in the Living Lab Ooijpolder

Since early 2021, the Ooijpolder has been a ‘living laboratory’ for Professor of Plant Ecology Hans de Kroon. The area is one of three living laboratories in the Netherlands that, over the next five years, will use a grant from the NWO (€3 million from the Dutch Research Agenda) to investigate how different landscapes can become more sustainable and diverse. In this project, De Kroon collaborates closely with farmers and other residents of the Ooijpolder. “I won’t get much changed as an ecologist working alone; that’s really something we have to do together. After all, an ecosystem extends further than just a patch of nature; you really need to organise the area as a whole.”

In 2017, De Kroon and his colleagues sounded the alarm: their research showed that three-quarters of the insects in nature reserves had disappeared. This created a widespread sense of urgency, also among farmers. “They know about the problem of declining biodiversity and want to contribute to reversing that trend”, he explains based on his many conversations with them. “But they set certain conditions and that is only logical: it’s their livelihood. If you just say ‘nitrogen up to this point and no further’, the debate becomes polarised. That’s why we’re keen to explore new possibilities together: what works for agriculture and for biodiversity?”
“Such a collaboration starts by asking lots of questions, not around a table but during field meetings with your feet in the mud: What is your ambition for this landscape in five or ten years’ time? What are you satisfied with and what would you like to change? How is your soil doing? Are there earthworms in it? How often do you fertilise and plough? In return, farmers ask us questions: what does an herb-rich meadow mean for the nutritional value and the yield, and will I have fewer problems with geese eating away at my field? These are all relevant questions that we try to address with research.”

De Kroon’s research has already shown that an abundant blanket of flowers goes hand in hand with safe dikes. “We always thought that if space was limited, one plant species would grow at the expense of another, but the opposite appears to be true. It seems as though the roots are cheering each other on; the species actually encourage each other.” That root strength ensures a solid ground layer and thus a solid dike cover.
In this way, fundamental research can lead to very practical applications. It also ensures that De Kroon, despite all the alarming climate reports, does not lose heart. “What gives me hope is that here in the Ooijpolder we can see the insect community flourishing again. It is possible if you do the right things.”

Hans de Kroon studied biology at Utrecht University, obtained his PhD from there in 1989, and has been Professor of Experimental Plant Ecology at Radboud University since 2000. Photo: Flip Franssen