Should polar bears be listed as endangered? A federal judge will hear arguments today from environmental groups who say yes, and from federal officials who say no.

In 2005, the Center for Biological Diversity submitted a scientific petition called for the polar bear to be listed as threatened under the Endangered Species Act, on the grounds that disappearing Arctic sea ice as a result of climate change put the species’ very existence at risk. When that call was initially met with inaction, the Center, in collaboration with Greenpeace and the Natural Resources Defense Council, filed suit.

The U.S. Fish and Wildlife Service responded in January 2007 by recommending the listing. As part of the review process, then-Secretary of the Interior Dick Kempthorne asked researchers with the United States Geological Survey to review the status of polar bears, particularly the three sub-populations in US waters. The results of the USGS study were unequivocal and stark:

Projected changes in future sea ice conditions, if realized, will result in loss of approximately 2/3 of the world’s current polar bear population by the mid 21st century. Because the observed trajectory of Arctic sea ice decline appears to be underestimated by currently available models, this assessment of future polar bear status may be conservative.

In January 2008, Kempthorne confirmed that the species would indeed be listed as threatened. But he added an important caveat, exempting greenhouse gas emissions and oil development from regulation under the ESA ruling. Given that those two activities were precisely the ones that environmentalists had argued were imperiling polar bears and their habitat to begin with, the Center and its partners promptly filed suit again, pushing this time for the species to be listed as Endangered, which would mandate an end to Kempthorne’s exemption.

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In October, Judge Emmett Sullivan heard arguments from the Obama Administration, which maintained its predecessor’s opinion, against an Endangered listing. According to the Associated Press, he found those arguments less than compelling:

He rejected the federal government’s contention that a species must be in imminent danger of extinction to be declared endangered. Such an “imminence” requirement was an erroneous conclusion, he wrote, and lawmakers intentionally left the law ambiguous to give regulators flexibility to respond to variable conditions. The law says a listing determination must be made on one or more of five factors. The first listed, and most relevant for polar bears, is the current or threatened destruction of habitat.

According to the National Snow and Ice Data Center, annual minimum sea ice extent in the Arctic is declining on average by 11 percent per decade; the IUCN Polar Bear Specialist Group says that eight of 19 polar bear sub-populations are “declining” (three are stable, one slightly increasing; there is insufficient data to determine the trends or status of the remaining seven).

Sullivan’s court will be in session again on Wednesday, as Administration attorneys, and the Center’s Kassie Siegel, who wrote the original petition, put forward their contrasting views on whether that information is sufficient to require that polar bears be listed as Endangered.

Discovery News will be at the hearing; we’ll be providing updates during the day and we’ll be speaking with representatives from both sides to gain insight into their positions and their predictions for how the judge will ultimately rule, and what that decision will mean. Stay tuned.

UPDATE: Wed Feb 23, 1:30pm EST: The court has heard arguments from plaintiffs on either side. From the Center for Biological Diversity and partners on one side; and the State of Alaska and partners on the other.

The former argued that the Fish Wildlife Service commissioned the best possible science when considering its listing of polar bears as threatened, but that in arguing against the species being endangered, it did not heed that scientific advice.

CBD attorney Kassie Siegel repeated and synthesized the available scientific information, all of which shows that sea ice is declining and which predicts severe reductions, and high probability of some population extinctions, by mid century at least.

On the other side, Alaska – joined by Safari Club International, Conservation Force and the California Cattlemen’s Association – argued that the threatened listing is unnecessary. They argued that population models are just that: they are models that by definition produce estimates. At present, they claim, polar bears are present throughout their range, they are plentiful, and they are reproducing successfully.

Hard to see which way the judge is leaning: He seems especially keen not to overstep his mandate, to respect legal precedent and not to take action that would establish further precedent.

The government will make its case after lunch.

UPDATE: Wed Feb 23, 5:30pm EST:

The final session of the day began with the government making its case. For the Administration, represented by counsel Cliff Stevens, it was a slightly awkward position. The government position is clear: polar bears are threatened, whatever the state of Alaska and its associates may assert, but they are not endangered, as the Center for Biological Diversity says. The decision to list them as threatened, in other words, was the right one, and therefore justice Sullivan need take no action, simply leave things as they are. But because he was facing plaintiffs from either side, Stevens found himself at times walking a tightrope, arguing against the position of the state of Alaska and others who claim the polar bear is not in danger of extinction, but at the same time trying to insist that it is not in imminent danger of extinction.

“To be endangered, a species has to be capable of becoming extinct today,” he argued. “The government’s position in a nutshell is that, given the number of polar bears and the extent of the species’ range, polar bears are not in danger of extinction.”

However, he continued (try and stay with me here), “they are likely to become endangered at the end of a reasonable and foreseeable period. So today, they are threatened. The polar bear is a classic case of a threatened species.” In other words, the government is arguing that polar bears will likely become endangered and at risk of extinction. But not right now.

To which Kassie Siegel of CBD retorted, “The standards the government is trying to set are arbitrarily high. Models predict an 80 percent chance of extinction (for some populations) in 40 years.

“The Western Hudson Bay population is not just in danger of extinction, it is in the process of becoming extinct.”

Unless Justice Sullivan makes a decision to support either plaintiff in the interim, the next step will be a hearing on April 13 to discuss the exemption to the threatened listing (known as the 4d rule), which then-Secretary Kempthorne added in order to have oil and gas exempt from the ESA restrictions. Although not much discussed today, that rule is really at the root of today’s arguments: without it, there would be little practical difference between the Threatened and Endangered listings.

At the end of the day, what does it all mean? Unless Justice Sullivan agrees with Alaska and its fellow plaintiffs, the polar bear will remain listed under the Endangered Species Act as threatened. The only question is whether it’s listing can be bumped up to endangered. And to some extent, that decision will revolve around one fundamental question: If a species is considered highly likely to be extirpated from much of its range in as little as 45 years, does that mean it is in imminent danger of extinction, or not?

IMAGE 1: E. Barrett Prettyman United States Court House. IMAGE 2: After being observed swimming in the open water off the coast of Alaska, far from the ice edge, this skinny polar bear climbed onto a passing ice floe. Photographs by Kieran Mulvaney.