Wetenschap - 8 maart 2019

‘A warm spring is risky for nature’

tekst:
Roelof Kleis

The exceptional warmth in February could have serious consequences for the water supply during the coming growing season.

Sunbathers in the Kronenburgerpark in Nijmegen op februari 25 2019. © Manon Bruininga|Hollandse Hoogte

And nature has not yet recovered from the drought of 2018. ‘We are entering uncharted territory now,’ says researcher Ryan Teuling of the Hydrology and Quantitative Water Management chair group.

Has nature recovered yet from the dry summer of 2018?

‘No. At the end of the summer the average precipitation deficit (rainfall minus evaporation, ed.) was about 300 mm. The winter was not extremely dry, but it did not rain enough to make up the shortfall. So we are lagging behind a bit this spring.’

If it stays relatively warm, evaporation will speed up. The available water will get used up much faster and all the water will be gone by the summer.
Ryan Teuling

 
What is the effect of such an extremely warm period in February?

‘The plants are not green yet, so evaporation is still low. But of course, moisture does evaporate from the soil due to those high temperatures. If that is 1 mm per day, then you lose 10 mm rather than gaining 10 mm in additional rainfall. A week or so of lovely weather like that doesn’t help. It adds up, especially on the higher sandy soils.’

 
Is the weather in the next month crucial?

‘The soils are still moist enough at the moment. But if it stays relatively warm, the leaves will come out early. And then, in three or four weeks’ time, evaporation will speed up. That is much earlier than normal. The available water will get used up much faster and all the water will be gone by the summer. That is not a problem in itself, but it does mean we mustn’t have a dry summer.’

Professionally, I still hope for a dry summer, but that wouldn’t be good news for the Netherlands.’
Ryan Teuling


And we don’t know about that yet?

‘We are living in a time of extremes. Temperatures have never been so high in February. We are now entering uncharted territory, in a climate zone that is new for us and for nature. Professionally, I still hope for a dry summer, but that wouldn’t be good news for the Netherlands.’


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