Federal judge rules that the government did not contravene the Endangered Species Act by failing to reduce emissions

The US government has not broken its obligation to protect the polar bear by failing to cut greenhouse gas emissions, a federal judge ruled on Monday.

The suit, brought by environment organisations – including Greenpeace, the Center for Biological Diversity, the Natural Defense Council and Defenders of Wildlife – hoped to use the Endangered Species Act (ESA) to force the Obama administration to act on emissions.

In 2008, the Bush administration listed the polar bear as an endangered species under the act, ruling it was at risk from melting ice caused by climate change.

For a long time the US government refused to see a link between climate change and threat to polar bears. Even when listing the bears as endangered, the former US secretary of the interior, Dirk Kempthorne, said: "While the legal standards under the ESA compel me to list the polar bear as threatened, I want to make clear that this listing will not stop global climate change or prevent any sea ice from melting. Any real solution requires action by all major economies for it to be effective. That is why I am taking administrative and regulatory action to make certain the ESA isn't abused to make global warming policies."

Despite Kempthorne's comments, under the ESA, the government is legally obliged to create a plan to protect the species. Green groups argue that this means the US government has a duty to force industry to cut its emissions.

A variety of oil industry and business groups, along with the governor of Alaska, opposed that stance, saying it would be impossible to draw a scientific link between, for instance, a new coal power plant in the US and the ice melting in Alaska.

However, the court decided on Monday that the government had met its obligations. US district judge Emmet G. Sullivan concluded that federal officials were within their authority in a rule allowing "incidental" harm to polar bears that might occur in the Arctic as a result of oil and gas activities.

"The question at the heart of this litigation – whether ESA is an effective or appropriate tool to address the threat of climate change – is not a question that this court can decide based upon its own independent assessment, particularly in the abstract," the judge wrote.

But he also found that the US government erred in not undertaking an environmental impact statement before it listed polar bears in 2008. The judge has asked the Interior Department to undertake an environmental review – it has until 17 November to do so.

Nobody knows the exact number of polar bears. While the population is estimated to be about 25,000 at the most, observations by biologists show a decline.

Conservationists said they were confident a new environmental review would show that global warming needs to be addressed in order to hasten the polar bear's recovery.

"The polar bear was the first species added to endangered species list solely because of threats to the species from global warming. The ruling does not limit the applicability of the ESA to greenhouse gas emissions affecting species listed as endangered under the act, or to other threatened species for which Interior has not issued a specific exemption," the plaintiffs noted in a statement.

The court' s decision was "bittersweet", one said.