Margrethe Vestager never expected the food sector would turn into a threat to her reputation as an ethical consumer champion.

When the Dane took over as the world's most powerful antitrust regulator in 2014, it seemed most likely her legacy as EU competition commissioner would be forged in high-profile showdowns with the likes of Google and Russia's gas export monopoly Gazprom.

Another potentially more formidable challenge has emerged with the €222 billion consolidation of the agrichemical sector that involves the industry's biggest players: Bayer and Monsanto, Syngenta and ChemChina, and DuPont and Dow Chemical.

Dow and DuPont are expected to offer sweeping concessions by Tuesday in an attempt to secure approval.

While Vestager's reputation has soared as the superstar of Jean-Claude Juncker's commission, these deals carry a health warning for her legacy and could undermine her green credentials.

“The great reputation that Vestager has … comes by showing that she doesn’t shy away from beating up Apple, Gazprom and McDonald’s,” said Margrete Auken, a Green MEP from the Danish Socialist Party. “There is of course a risk that this reputation will suffer if she accepts consolidation of such magnitude.”

“These are mergers between our biggest enemies” — Philippe Lamberts

People close to Vestager admit the political stakes but caution that her ability to block these kinds of mergers is severely constrained. She can demand changes to the deals over concerns about prices and fair play in the market, but not the environment.

But it is the environment that is shaping the public debate. Campaigners ranging from environmentalists to Michelin-starred French chefs are out to torpedo the mega-mergers and argue the companies involved are lobbyists for pesticides and genetically modified foods. They fear the sweeping sectoral concentration of power will not just increase prices for farmers, but also lessen biodiversity and erode Europe's rural heritage.

“These are mergers between our biggest enemies,” said Philippe Lamberts, a Green MEP from Belgium. “These guys do the maximum to increase profits at the expense of public health, like the cigarette companies.”

Lamberts said the cases had to be considered in the same context as the European left's opposition to free-trade deals with Canada and the U.S. He described the battle against the agricultural deals as part of the same "democratic fight of today."

Joining the recent groundswell against trade deals, thousands of campaigners have bombarded Vestager online asking her to block what they call Bayer and Monsanto's #mergerfromhell, and more than half a million people globally have signed a variety of petitions against the deal. A spokesperson for Vestager declined to comment.

Too big to control

In recognition of the public concerns, EU regulators in late January took the unusual step of writing to reassure petitioners that the merger will not escape scrutiny.

In a quirk of history, a similar sentiment led to the founding a century ago of Vestager’s political party, the Radikale Venstre, by small peasant farmers opposed to the power of large farming interests.

“Margrethe will be suspicious of the economic interests of big agriculture and their political privileges,” said Kasper Fogh, head of politics with Danish think tank Cevea.

It is difficult to exaggerate the dizzying range of European farm and food businesses that will be affected by the mergers. The deals will have implications for tens of thousands of products, ranging from pesticides targeting nematode worms in Portugal to oil-seed rape seeds sold to be cultivated in Greece.

Given this complexity, Vestager will be hard pressed to evaluate every possible repercussion of the deals. Indeed, she has only just over two dozen officials to crunch through the minutiae of three extremely technical mergers: Bayer's $66 billion takeover of Monsanto, which will be filed to regulators in the coming months, ChemChina's $43 billion swoop on Syngenta, which has an April 12 decision deadline, and the $130 billion tie-up between Dow and DuPont.

Still, there is no sign that Vestager's team lacks the stomach for a fight: Objections delivered to the tie-up between Dow and DuPont in December are said to be among the longest ever filed by merger-busters, coming in at close to 1,000 pages.

One of her biggest challenges is that it is fairly easy for agri-chemical companies, like pharmaceutical giants, to wriggle through competition concerns. They tend to have so many products, spread across so many countries, that there is plenty of room to sell off assets to escape an outright block on the grounds on excessive market power.

Competition regulators tend to wield their veto against deals that leave just three main operators, but the agrichemical mergers will continue to face competition from big firms like BASF, a German chemical company, and Vilmorin, a French seed developer, plus smaller players.

Still, Vestager can take heart from indications that it is not just Europe having doubts. Members of the transition team of U.S. President Donald Trump expressed worries, while Chinese regulators are also studying complaints filed by concerned citizens, including reportedly a former minister for the chemical industry, Qin Zhong-da. Each deal will need approval from regulators in the U.S., China and a host of other jurisdictions.

The greening of industry

The industry argues that activists' fears are misguided. They retort that the mergers bring together largely complementary portfolios. This will save money, allow more investment and help the companies collaborate internally in developing pest-resistant seeds and powerful weed-killers. Such cross-pollination, they argue, will push down prices and drive innovation.

"Those merging have less overlapping, and more complementary interests. In the case of the Dow/DuPont merger for example, it will combine a strong crop protection portfolio with one that is more specialized in seed production," said Robert de Graeff, policy officer for the European Landowners' Association, a large-scale agricultural lobby in Brussels.

Similarly, Syngenta is a big innovator in pesticides while ChemChina's business portfolio in Europe largely consists of the Israeli company ADAMA, which is a generic manufacturer and has no unique products. It has offered to sell several business lines, including insecticides and pesticide brands in Europe, and is on track to win approval, according to an adviser following the deal.

"The livelihood of farmers depends on access to seeds and crop protection at competitive prices" — Margrethe Vestager

As for Bayer and Monsanto, the latter is the undisputed global market leader in seeds with a limited presence in Europe, while Bayer possesses a leading position in the pesticide industry and a uniquely strong position on the Continent.

Vestager has sounded more alarmed about the synergies in her review of Dow’s tie-up with DuPont, which was the first to file for clearance from Brussels. The Commission worried the two would be able to raise prices for key agricultural products such as nematicides, chemicals that protect against roundworms infecting crops ranging from soybeans to figs. They have also zoned in on the companies' innovation pipelines, fearing the tie-up will lead to fewer new products.

"The livelihood of farmers depends on access to seeds and crop protection at competitive prices," Vestager said when listing her objections in August. "It's a very concentrated sector already," she warned more recently on Bloomberg TV.

The chief executive of DuPont, Edward Breen, said in late January that the parties were negotiating a wide-ranging package in a last-ditch effort to resolve Commission objections ahead of a March 14 decision deadline, including concerns about innovation.

But Dow argued the deal would make it more agile. "The new company will be a stronger innovator able to better compete not only with the largest multinational companies but also all of the other competitors in the crop protection industry, which is something that neither company has been able to achieve on its own," the company said in a statement.

Margins do appear squeezed at the top. Syngenta saw gross profits fall 8.4 percent in 2015 compared to the previous year, and net income at DuPont in 2015 slipped to $1.95 billion compared with $3.63 billion in 2014.

Environmentalists want to push the agenda beyond the logistics of merger regulation to warn about broader changes to the way Europe's food is produced. Green MEPs released a report last year showing 95 percent of the European vegetable seed market is now controlled by just five companies.

Should the three deals go ahead, “together the resulting companies will hold a monopoly over the EU's food supply chain,” said Adrian Bebb, a campaigner for Friends of the Earth. “This will have a massive impact on choice and price for both farmers and consumers, as well as creating a massive lobby power for more industrialized agriculture."

The companies are kicking back hard against that vision.

A spokesperson for Bayer said there are "currently thousands more companies in the seed market than those that appear in news reports and there will never be a single seller that is dominating everything." Monsanto declined to comment.

A Syngenta spokesperson said its ChemChina merger was driven by concerns over low commodity prices and the costs of regulation and research and development. ChemChina did not respond to requests for comment.

Bayer's spokesperson flaunted the company's green credentials too, arguing that in addition to increasing production, technological advancements are "making agriculture more sustainable by cutting fuel emission, reducing soil erosion, conserving water use and minimizing potential runoff while increasing the biodiversity of beneficial organisms, which thrive in healthier environments."

But that does not wash with the companies’ opponents.

Vestager “has been quite clear that we cannot give up too much power to multinationals,” said Rasmus Nordqvist, a Danish member of parliament for The Alternative, a green party. “That’s why I have hope.”

This article was updated to clarify that Vestager's office did not comment on the merger cases.