Cattle graze near the Sacramento Municipal Utility District's Rancho Seco Nuclear Power Plant near Herald, Calif. (AP Photo/Rich Pedroncelli)

It's no secret that there has long been suspicion, on the political left, about nuclear power. Research has often shown that liberals, more than conservatives, distrust or oppose nuclear energy, even though many of the more dramatic claims about nuclear risks appear to be exaggerated.

That's why a new letter, signed by 71 ecologists and conservation researchers (at last count), may be so significant. Authored by ecologists Barry Brook of the University of Tasmania and Corey J.A. Bradshaw of the University of Adelaide -- and based on a longer paper by the two just out in the journal Conservation Biology -- it argues that greens must rethink their nuclear power resistance. That's especially the case, the letter says, when it comes to "advanced nuclear power systems with complete fuel recycling" -- a technology intended to help minimize one of the chief problems with nuclear power (the waste). (For a technical paper from the International Atomic Energy Agency on the prospects for reprocessing spent nuclear fuel, see here.)

"We entreat the conservation and environmental community to weigh up the pros and cons of different energy sources using objective evidence and pragmatic trade-offs," reads the letter, "rather than simply relying on idealistic perceptions of what is ‘green.’" It argues that while wind and solar are very promising energy technologies, they may not, on their own, be enough -- and that "nuclear power -- being by far the most compact and energy-dense of sources -- could also make a major, and perhaps leading, contribution." (Nuclear power gives off virtually no greenhouse gas emissions -- although the processes of extracting uranium, and building nuclear plants themselves, certainly do.)

The two main authors of the letter -- Barry Brook and Corey Bradshaw -- have considerable green cred. They are widely published in the conservation field, most recently having authored a prominent paper suggesting that efforts to reduce the global population would not have a significant impact on staving off wildlife extinctions and other ecological damage.

This is not the first time that a coterie of environmental scientists have stood up for nuclear energy. Last year, four top climate researchers -- Ken Caldeira of the Carnegie Institution, Kerry Emanuel of MIT, Tom Wigley of the National Center for Atmospheric Research, and James Hansen of the Earth Institute of Columbia University -- wrote a letter defending the deployment of what they described as newer, safer nuclear power technologies, remarking that "in the real world there is no credible path to climate stabilization that does not include a substantial role for nuclear power."

"The risks associated with the expanded use of nuclear energy are orders of magnitude smaller than the risks associated with fossil fuels," the letter added.

Nuclear power defenders frequently point to France -- a nation that is certainly to the left of the United States politically, and yet gets more than 70 percent of its energy from nuclear power. This example, like the letters above, suggests that nuclear power is no simple left versus right issue -- there is a lot of support for nuclear power among academic scientists in particular.

Nonetheless, when it comes to the advocacy for an expansion of nuclear power, there is an important counterargument -- nuclear power deployment is very costly. The environmental scientists don't directly address cost in their letter, but Brook and Bradshaw do in their larger paper in Conservation Biology, arguing that "the standardized, compact, passive-safety blueprints of next-generation nuclear power plants....have the potential to be transformative."

But according to Edwin Lyman, a senior scientist with the Union of Concerned Scientists who works on nuclear issues, there are many problems with the environmental scientists' letter -- and especially with the idea of reprocessing or recycling spent nuclear fuel, which is central to the new conservation scientists' letter. "Reprocessing is a dirty, dangerous and proliferation-prone technology," said Lyman. (The UCS's critique of spent nuclear fuel reprocessing can be found here.)

"A scientist above all should understand that if something sounds too good to be true, it probably is!" Lyman continued.