On the agenda is life on earth, in all its forms and diversity. The big question is how far nations will go to stop the disastrous declines underway.

Representatives from more than 175 countries are gathering to negotiate answers, starting on Monday in Cali, Colombia, at what is expected to be the largest United Nations biodiversity conference in history.

How the talks unfold over the next two weeks will help determine, for better or worse, the planet’s future. Biodiversity is declining faster than at any time in human history, an intergovernmental panel of scientists found in 2019. It estimated that a million species were in danger of extinction. Even many common species are in decline. Bird populations in the United States and Canada, for example, are down almost 30 percent since 1970, with widespread losses among some of the most frequently seen species.

The biggest driver of declines in biodiversity on land is habitat loss, mainly when land is taken for agriculture, the panel found. In the ocean, it’s overfishing. Climate change plays an ever-growing role, and the two crises are intertwined.

Such drastic losses of biodiversity threaten human well-being, scientists warn. Forests filled with birdsong also stash away planet-warming carbon, filter water and create rain. Healthy rivers and oceans run with fish that people need for food. Insects nourish soil and pollinate plants; birds and mammals disperse seeds, plants turn sunshine into food for the rest of us.

“When we destroy biodiversity, we are destroying the very links that help the system to reproduce life,” said Susana Muhamad, Colombia’s environment minister, who will be presiding over the conference. “What is at stake is actually another wave of extinction, which could be the sixth general extinction on Earth.” The last one wiped out the dinosaurs.