Higher dikes no solution for the Netherlands in the event of stronger warming

“All CO2 emissions to date may already lead to a warming of more than 2 degrees”, a new study shows. “Future emissions are added to that. Such a high level of warming has major consequences for the Netherlands”, warns Professor of Physical Geography Maarten Kleinhans of Utrecht University.

Last Thursday, Royal Netherlands Meteorological Institute (KNMI) director Gerard van der Steenhoven expressed his concerns about the threat of exceeding the limit of 1.5 degrees of warming, and called on the new government to take a step further to combat global warming.

We would now be heading for 3 degrees of warming. “That will lead to a dramatic situation. Everyone will have to realise that we need do something now”, says Van der Steenhoven.

The KNMI recently referred to a study that shows that global warming resulting from past emissions may be greatly underestimated. Areas that warm up more slowly, such as the Southern Ocean, are eventually catching up, which (via changes in cloud cover) can amplify global warming.

A warming to 2.3 degrees would therefore be inevitable. The warming caused by future CO2 emissions is added to that.

Ice sheets near tipping point

The consequences of climate change will increase disproportionately as global warming turns out to be higher. In addition, many consequences, such as sea level rise, have been greatly delayed. This is due to the slow reaction of ice sheets, which are now losing ice at an accelerated rate . At some point, that meltdown can reach a tipping point, after which ice sheets can disappear almost completely. For Greenland and West Antarctica, these tipping points are probably between 1.5 and 2 degrees.

“An inescapable consequence of 3 degrees for the second generation after us is unstoppable sea level rise. And with the sea, the rivers rise over the entire width of the Netherlands. In the river area we now protect cities during extremely high water by discharging water into sparsely populated polders, but with backwater by seawater that makes no sense anymore. “

These rivers make the Netherlands a delta: the estuary of the Rhine, Maas, Scheldt and Ems on the North Sea. Natural processes can keep such a delta in balance and even absorb some sea level rise.

Dikes are causing the country to sink

But those natural processes are no longer allowed, says Kleinhans. The problem is our dikes; that prevent rivers overflowing and entering the sea at every high tide. But those (minor) floods made our country precisely by depositing clay. That hasn’t happened for centuries.

We also dewater our peatlands. Both have the result that the bottom continues to settle and subside, and half of the Netherlands is therefore increasingly deeper – behind ever higher dikes. More and more drainage is therefore also needed to keep the polders dry, but this drainage means that salt seawater is sucked in under the dikes. That saline groundwater in turn has major consequences for agriculture.

Kleinhans calls wild ideas to build a dam around the Netherlands nonsensical. “In the fierce plan of a thick wall around the entire Dutch coast, we have to pump the rivers mechanically to the sea and those pumps must never fail. But shipping needs locks, and they can fail, not to mention the ecological consequences. When combined with combating the other effects of climate change, the costs are also becoming astronomical. ”

Less emissions and controlled flooding

According to Kleinhans, it is therefore a better plan to tackle the problem at the real source: greenhouse gas emissions. In addition, instead of increasingly higher dikes and ever deeper polders, an attempt must be made to raise the land slightly locally.

“Along the Scheldt and Eems, this can be done with controlled flooding, in so-called exchange polders . We have a water policy in the Netherlands, but should also pursue a ‘sediment policy’ – to stop the sinking of the Netherlands.”

Original publication in Dutch on nu.nl (link). Dutch text credit: Rolf Schuttenheim, translation by groundstation.space