BRET BAIER (ANCHOR): Many environmentalists are in a panic tonight over a new report suggesting one million animal and plant species are at imminent risk of extinction -- and humanity is to blame. As in all such cases, some humans say the report and the response are exaggerations. Senior correspondent Eric Shawn takes a fair and balanced look tonight.

ERIC SHAWN (SENIOR CORRESPONDENT): The United Nations presented the report in Paris with dancers and music evoking the vibrancy of life on Earth, then showing what it says will happen if we do nothing: darkness, silence, and death from mother Earth. That prediction from the U.N. science policy biodiversity study. It says nature is threatened at, quote, “rights unprecedented in human history” and “living species face being wiped out.”

ROBERT WATSON (U.N. SCIENTIFIC PANEL CHAIRMAN): If we want to leave a world for our children and grandchildren that has not destroyed by human activities, we need to act now.

SHAWN: The group of scientists behind the study blame the burning of fossil fuels, pollution, and urbanization. Among their conclusions, greenhouse gas emissions doubling since 1980 and one million animal and plant species threatened by extinction.

WATSON: We need to slow down the loss and degradation of our natural habitats. Our forest, our wetlands, our grasslands, our coral reefs and along with this we need to slow down the extinction of species.

SHAWN: How to turn it all around? The report says stop wasting food, reduce the amount of water consumed, and improve the way electricity is generated. Critics say the report is over-the-top, alarmist, and exaggerates the consequences.

MARC MORANO (CLIMATE DEPOT): This is politics, not science. The U.N. is trying to expand its base to include climate and species. They are looking for more treaties, more regulation. They have identified a problem, they've juiced it up, and put themselves in charge of solving the problem. That is called a self-interested lobbying organization.

SHAWN: While the report presents an ominous future, its authors says it's up to the world's governments to change course, even as others claim the U.N.'s predictions of doom are far from plausible. Bret.

BAIER: Eric Shawn in New York. Eric, thanks.