ZAANDAM, Netherlands (AP) – Dutch farmers angry at government plans to slash emissions used tractors and trucks Monday to blockade supermarket distribution centers, the latest actions in a summer of discontent in the country’s lucrative agricultural sector.

The Netherlands’ busiest aviation hub, Schiphol Airport, urged travelers to use public transport to get to its terminals amid fears that the blockades also would target airports. Fishermen acting out of solidarity with farmers also blocked a number of harbors.

The unrest among Dutch farmers was triggered by a government proposal to slash emissions of pollutants like nitrogen oxide and ammonia by 50% by 2030. Provincial governments have been given a year to formulate plans to achieve the goal.

04 July 2022, Netherlands, Gieten: The license plates on the tractors were removed to prevent prosecution. In protest against planned environmental regulations, farmers in the Netherlands blocked supermarket distribution centers. With tractors and hay bales they blocked the access roads in several places in the country. Photo: Lars Klemmer/dpa (Photo by Lars Klemmer/picture alliance via Getty Images)

The license plates on the tractors were removed to prevent prosecution.(Photo by Lars Klemmer/picture alliance via Getty Images)

That is expected to lead to reducing livestock and buying up some farms whose livestock produce large amounts of ammonia. Farmers argue they are being unfairly targeted and shown little concern for their futures.

Police looked on but did not immediately take action Monday as some 25 tractors parked outside a distribution center for supermarket chain Albert Heijn in the town of Zaandam, just north of Amsterdam. Placards and banners affixed to the tractors read messages including, “Our farmers, our future.”

The umbrella organization for supermarkets called on police to take action and warned of possible shortages on supermarket shelves.

“Blockades of distribution centers hurt the citizens of the Netherlands. Supermarkets do everything they can to keep the stores stocked, but if blockades continue, it could lead to people not being able to do their daily shopping,” the Central Bureau for Food Trade said in a statement.

Traffic authorities warned motorists to prepare for delays and possible slow-moving tractors on the nation’s highways, but said that there were few problems early Monday for commuters, possibly because many people opted to work from home rather than get stuck in traffic.

Over the weekend, the government appointed an intermediary to lead talks between farmers’ organizations and officials drawing up pollution reduction measures. However, Prime Minister Mark Rutte has ruled out negotiating with farmers responsible for radical protests.

Mainstream farming lobby group LTO described the mediator, Johan Remkes, as “an administrative heavyweight with deep knowledge” of the issues and said it was open to talks with him.

According to LTO, there are nearly 54,000 agricultural businesses in the Netherlands with exports totaling 94.5 billion euros in 2019.

Farmers block the access to a Jumbo distribution center during a demonstration against the government’s far-reaching plans to cut nitrogen emissions in Nieuwegein, The Netherlands, on July 4, 2022. – The Netherlands, the world’s second-largest agricultural exporter, is one of the top greenhouse gas emitters in Europe — especially of nitrogen — with much of this blamed on cattle-produced manure and fertiliser. – Netherlands OUT (Photo by Robin van Lonkhuijsen / ANP / AFP) / Netherlands OUT (Photo by ROBIN VAN LONKHUIJSEN/ANP/AFP via Getty Images)