In today’s Senate showdowns, there’s plenty to be anxious about on the enviro front. Muckraker’s got the nitty gritty on key races here, but a quick rundown of races to watch out for:

In Montana, there’s incumbent Republican Conrad Burns and challenger Jon Tester, a race that has been the focus of plenty of attention as the election draws neigh. Burns is a particularly loathsome candidate for environmentalists thanks to his outspoken denial of climate change and a paltry 4% lifetime score — on a 100-point scale — from the League of Conservation Voters. Tester, on the other hand, led the fight last year to pass a law in state legislature requiring Montana to get 15 percent of its energy from renewables by 2015. He’s a former school teacher, an organic farmer, and his television ad series includes several shots of him testifying to the need for renewable energy while standing in the middle of a wind farm. Most of them also show Tester walking around town dressed in Carhartts, to keep Big Sky staters from writing him off as some sort of hippie.

Minnesota’s Senate race pits Democrat Amy Klobuchar against Republican Mark Kennedy, who’s racked up a grievous environmental record during his time in the House — including voting in favor of logging and against endangered species protection. Klobuchar has spoken in favor of energy independence and limiting greenhouse gas emissions, and earned the endorsement of the League of Conservation Voters — but not that of the Sierra Club.

In Washington State, Senate candidate Maria Cantwell has had some great environmental ads as well, including one on taking care of the Puget Sound and another on investing in renewable energy. Heralded as an enviro champion in her own right, it’s also not hard for her to look extra-green next to Republican challenger Mike McGavrick, whose campaign has been quite flagrantly funded by Big Oil — even if he did return some of it.

And in Pennsylvania, another particularly odious Senate member for enviros, Rick Santorum, is up against Democratic challenger Bob Casey, the state’s treasurer. Though Santorum does have this wonderfully ridiculous TV ad that mentions his commitment to open space, Casey’s unquestionably won the approval of, well, everyone who’s glad he’s not Rick Santorum.

And though stem-cell research has been the national-level hot-button issue in Missouri, environmentalists are also getting hyped about the prospect of defeating Jim Talent, another LCV Dirty Dozener [PDF]. His advocacy of ANWR drilling and denial of climate change has made Democratic challenger Claire McCaskill’s green leanings decidedly appealing for enviro voters.