The short version:
If you're a Sierra Club member, when you get a ballot from the Sierra Club in the next couple of weeks, please fill it out, and vote only for those people who have been endorsed by the nominating committee, as a bunch of anti-immigrant people are trying to mount a "stealth" takeover of the Sierra Club.
The long version:
Why this election is so important:
The Sierra Club is a democratic group: the Board of Directors, which determines what the club stands for, is elected by the membership. While being democratic is a good thing overall, it makes the organization vulnerable to a takeover by people groups hostile to our interests.
In the last election, and in this one, people who have very strong anti-immigrant positions are running as "stealth candidates" for the board: they aren't advertising their positions, but some managed to sneak on in the last election cycle, and if three of them win this time around, they'll get control of the Board of Directors of the Sierra Club. Currently the Sierra Club is neutral on immigration.
Even if you support tighter controls on immigration, the Sierra Club is the wrong group to be in this fight! Over the last decade, the environmental community has made important steps in reaching out to African-American and Latino communities. This needs to be done in order to broaden the political base for environmental protection.
Quite simply, if the anti-immigration wing takes over the Sierra Club, it will be a disaster. Now only will it make it much harder to reach out to minorities, but it will appear to confirm all of the worst stereotypes of environmentalists: that we don't care about people, that we're an over-privileged whites-only club, and even the "racist" slur may stick. This would be a disaster for the environmental movement, as it would make it much harder to fight for the important issues.
What needs to happen:
The Sierra Club has a "nominating committee", which endorses various candidates for the board. The nominating committee recognizes the danger posed by the anti-immigrant group, and is not endorsing them. When you get the ballot, PLEASE vote only for those candidates who have been endorsed by the nominating committee, and send in your ballot right away!
The big danger is that most members will remain in the dark about the danger facing the club, and will toss their ballots into the recycle bin. Again, many of the anti-immigration candidates are not advertising their positions.
I got this information from a conversation with someone who works for the Sierra Club. Unfortunately, it's against the rules for Sierra Club employees to talk on-the-record about the Board Elections, so I can't name names.