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The New Zealander Merrin Whatley (born 1980) will be receiving her doctorate at the UvA on 13 May. Her doctoral research at the Institute for Biodiversity and Ecosystem Dynamics (IBED) found that the plants and macrofauna of the North Holland polder landscape are in a poor state.

What did you do?

‘I researched the canals in the polders north of Amsterdam. I looked at the plants in and alongside these canals, and at the macrofauna. Macrofauna are invertebrates visible to the naked eye, such as snails and insects. I used data from the regional water board – the Hoogheemraadschap Hollands Noorderkwartier – and took my own samples too. This revealed that between 1990 and 2007, the average number of plant varieties per canal dropped from 14 to 8. The average number of varieties of macrofauna dropped from 45 to 22 between 1985 and 2007. In some canals, only mosquito larvae and amphipods remained. It was known that natural life in the polders was under threat, but we didn’t know it was quite so bad.’

What is the problem?

‘The levels of minerals such as phosphates and sulphate are too high in the water. These materials contribute to peat breakdown, and that breakdown releases more minerals. Peak breakdown has been going on for centuries as a result of drainage, but the higher concentration of minerals is leading to unforeseen consequences. It leads to murky water and a thick layer of muck at the bottom of canals. Plants and animals can’t cope with this. Intensive fertilisation contributes to faster breakdown, and so does the strong inflow of river water from the Rhine and mowing shorelines. These have all worsened conditions.’

Are your findings bad news?

‘On the one hand, yes. It’s a shame that the water quality of the polders is so bad. On the other hand, there is also good news: the solution is not really that complex. We don’t need to manage things differently or more intensively; rather, it should be less so. I argue for what’s known as soft management. Of course, you can’t let the whole polder landscape flood in order to protect a few species of plant or animal. But you can pump less, and isolate some canals. In isolated canals, the water quality rapidly improves. The canal edges also don’t have to be mown every year. Once every two years is enough.’

The Caenis robusta mayfly, which lives in the canals of North Holland. Illustration: Nigel Upchurch

How was your experience of completing your doctorate?

‘I learnt a lot. You learn a lot about yourself, like how you react in different situations. Will I carry on in research? Probably not. I’m going to go travelling with my husband for half a year first. Then we’ll be returning to New Zealand. I’d like to go back to work as an ecological consultant there. I think I’ll be able to put my knowledge of the effects of intensive land management on water ecosystems, which I acquired during my doctorate, to good use. New Zealand also has managed pastures. Ecology and nature as a whole continue to interest me. Look at mayflies, for instance. They’re one of the first animal species to have emerged onto land from water. The way they’ve been able to keep adapting so they're still around today, isn't that something to admire?'

Author: Carin Röst