Ministers from Britain, Canada, France, Germany, Italy, Japan and the United States gathered for the two-day meeting in the northeastern city of Metz.
They were due to discuss measures to tackle deforestation, plastic pollution and the degradation of coral reefs and try to form alliances between nations to act on them.
Joining the ministers were delegations from the European Union as well as Chile, Egypt, the Fiji Islands, Gabon, India, Indonesia, Mexico, Niger and Norway.
“We need to come out of this G7… with some very concrete things that go beyond speeches,” said France's junior minister for ecological transition, Brune Poirson, as the meeting opened.
On Monday, the UN will publish an executive summary of a 1,800-page tome crafted by more than 400 experts — the first UN global assessment of the natural world in 15 years.
Drafts of both documents obtained by AFP leave no doubt that it will paint a disturbing picture of widespread destruction wrought by man, some of it irreparable.
“We will agree on the best ways to enhance the place of biodiversity on the international stage…,” said France's Minister for Ecological Transition, Francois de Rugy.
But Andrew Wheeler, the former coal lobbyist appointed by President Donald Trump to head of the US Environmental Protection Agency (EPA), told the meeting too much attention was being paid to the worst-case scenarios on climate change.
Outside the meeting, environmental campaigners “Alter G7” demonstrated to highlight what they say is the urgency of the global crisis.