When celebrity environmental activist Nicolas Hulot agreed to join Macron's government upon his election last year, campaigners dared to hope for a radical shift towards greener policies.
Hulot, a TV star and veteran campaigner, had rejected previous job offers from presidents but decided to give Macron the benefit of the doubt, even though he had voted for the centrist's Socialist rival.
"We'll have to see if his conversion (to the environmental cause) is coherent, honest and credible or not," Hulot said at the time.
The 63-year-old was under no illusions: he knew he was joining the government of a country with powerful farming and industrial lobbies, and one which gets 70 percent of its electricity from nuclear power.
Ministry of the Impossible
France has seen 13 environment ministers in 20 years. Robert Poujade, the first man to hold the post, quipped in the 1970s that a better job title would be "minister of the impossible".
Resigning live on air Tuesday -- without warning Macron first -- Hulot said he had grown frustrated with apparently irreconcilable differences between his vision and that of the government.
"We don't see things through the same lens," he said of Macron, a former investment banker, and his conservative Prime Minister Edouard Philippe.
"They don't understand that the dominant model is to blame," he said in his resignation interview. "We are chasing growth at all costs."
The shock announcement was an unwelcome addition to a long list of political difficulties for Macron, who defended his record on the environment.
"In 15 months this government has done more than any other in the same amount of time," he insisted.
Macron's environmental policies under scrutiny
Macron's government won plaudits from campaigners for a landmark legal ban on fossil fuel production by 2040 and by scrapping a proposed new airport at Notre-Dame-des-Landes in western France, partly on environmental grounds.
But critics say that these polices were just a cover-up for hardline liberalism, and that Hulot was just a showpiece.
"He tried, but he would never have been able to have his voice heard in a government for which the environment is just a facade," added Jean-Francois Julliard, head of Greenpeace France.
Hulot was forced to announce in November that France's long-held goal of bringing its reliance on nuclear energy down to 50 percent by 2025 was not feasible, and would likely take a decade longer.
Paris backed a European law on chemicals known as endocrine disruptors which activists said was too lax, and an EU-Canada trade deal, opposed by Hulot on environmental grounds, came into force in September.
Most recently he clashed with cabinet colleagues over a decision not to write into law a ban on glyphosate, a herbicide which the World Health Organization says likely causes cancer.
Members of Macron's centrist Republic On The Move (LREM) party have accused Hulot of being too impatient.
Hulot brushed such comments aside.
"We've been patient for 30 years," he said.