Dutch farmers blockaded supermarket distribution centres on Monday in continuing protests at new environmental rules on nitrogen emissions that are likely to put many of them out of business. Fishers blocked ports in a show of support for farmers. The blockade prevented ferries from sailing to almost all the Wadden Islands off the country’s northern coast and caused lengthy delays, shipping companies reported. However, the port of Rotterdam, Europe’s biggest harbour, wasn’t affected. Farmers used tractors and large bales of hay to block entrances to more than 20 supermarket distribution centre…