As you may have heard, President Obama is being cagey about whether he’ll attend the Earth Summit in Rio next month. You know, it’s just the FUTURE OF THE PLANET that’s up for discussion. Nothing big. Maybe he’ll go. Maybe not.

As it happens, we were in the same situation 20 years ago, as the 1992 Earth Summit approached and George Bush Sr. was giving it the old, “Well, maaaaaybe …”

Back then, a group of the major, mainstream environmental groups in the U.S. rallied for the cause. To convince Bush he should attend, they enlisted none other than Darth Vader. Well, his voice, at least — the actor James Earl Jones. They made the spooky film clip below, replete with — is that the Pony Express or the Horsemen of the Apocalypse? — and then ran it in movie theaters around the country. Jones did the voiceover. Need I even tell you that Bush Sr. decided to attend?

In my research into the 2012 Earth Summit, I’ve noticed very little action from the major U.S. greens. A handful of them, including EarthJustice, the Natural Resources Defense Council (NRDC), the Nature Conservancy, and the Pew Environment Group, have been involved, along with groups focused on clean energy, sustainable agriculture, and other issues, but where’s the old guard that sponsored the Darth Vader ad two decades ago? I decided to do a little poking around.

In the credits, the Darth Vader clip lists seven green groups: The National Audubon Society, Defenders of Wildlife, the Earth Day Network, the Wilderness Society, the Sierra Club, the Rainforest Action Network, and NRDC. I spent some time poking around each group’s website, and reached out via email and phone to see what they’re doing for Earth Summit 2012. Here’s what I found:

Audubon Society: The website of this bird conservation stalwart featured stories about Burmese pythons in the Everglades and how to “celebrate Mother’s Day with puffins,” but I could find no mention of the Earth Summit. I sent an email to three staffers and received only this reply, from Taldi Walter, the group’s assistant director of government relations: “Nothing on my end.”

Defenders of Wildlife: This national nonprofit’s website included information about saving wolves and sea turtles, but nothing about the Earth Summit. In response to my query, Cindy Hoffman, vice president of communications, sent me links to several helpful sites, but said, simply, “Thanks for reaching out. No, we are not involved with the summit.”

Earth Day Network: Most of this group’s website is focused on, you guessed it, Earth Day, but some digging around unearthed this page with some useful background about the Earth Summit and mention of the group’s Women and the Green Economy campaign. The big “GET INVOLVED” button on the page just sends you to a general signup page, however, with no further information about the summit. A network spokesperson promised to set up an interview with the group’s president, Kathleen Rogers.

The Wilderness Society: The website for this most crunch-tastic of green groups headlined actress Wendie Malick and her fight to protect wild “pockets of wonder,” and the mama duck who is nesting in the planter outside the organization’s Washington, D.C., offices. There was nada about the Earth Summit on the site. I asked Senior Communications Director Kitty Thomas if the group was doing anything for the Earth Summit and she replied, “I checked and it looks like we aren’t.”

Sierra Club: This venerable green giant is doing more to engage with the Earth Summit than any other of the groups I talked to, save NRDC, but you’d never know it from looking at its website, which featured links to videos of celebrities talking about their “favorite piece of America” and Mother’s Day specials from the gift shop.

Justin Guay, with the club’s international program, told me the group is focusing its limited resources on promoting clean energy access for the world’s poor — a major priority for the U.N. The club has spearheaded two letters from business representatives and environmental groups asking the World Bank to commit to funding clean energy, and will hold a side event in Rio advocating for solar and other clean energy sources in the developing world.

I also spoke with Quentin James, national director for the Sierra Student Coalition, the club’s youth arm. James told me the coalition had just selected a group of delegates that will attend the summit, but could not offer a clear agenda beyond “trying to make sure that young people’s voices are heard on all the issues.” He also said they’d be pushing for action on climate change, but discussion of the climate is all but verboten at the official Rio talks — it has its own set of international summits, the most recent of which was held in Durban, South Africa, this past December.

Rainforest Action Network: This group’s website boasted of a stunt in which activists used a banner to “rebrand” the Bank of America football stadium in Charlotte, N.C., “Bank of COAL” (Buuuurn!) and a campaign to save the Sumatran orangutans. I could find no mention on the site of the Earth Summit, nor even the current shit storm brewing over Brazilian rainforest protection. A query for more information got no response.

NRDC: I happen to know that NRDC has been working fervently behind the scenes during the lead-up to the Earth Summit, but there was no mention of that on the group’s homepage, which featured a pop-up ad for “Green Gifts for moms and Mother Earth” with pictures of cute animal babies and their mammas. Nor could I find the Earth Summit on the “issues” page. There was no mention on the “policy” or “international policy” pages. Nada on the “act now” page. To find any mention of the Earth Summit, I had to dig into the staff’s numerous blogs. Sort by “issues” and you’ll find, in the long list, “Race to Rio.”

There you have it: For even the most active of these traditional American Big Green groups, the Earth Summit isn’t frontpage news. For most of the old school greens, it’s not news at all.

Jacob Scherr, NRDC’s director of global strategy and advocacy, who is heading his group’s Earth Summit work, assures me that even though the summit gets little love on the website, his efforts are receiving solid support from inside. He has a team of about 20 people working on the summit.

But what about the rest of the old guard? Several of them, including NRDC, the National Wildlife Federation, and the Sierra Club signed a letter in September 2009 urging President Obama to support holding the Earth Summit, and Scherr tells me he is optimistic that more U.S. green groups will get on board as the meeting approaches. But time is running short.

I can think of a couple of reasons that U.S. environmental groups aren’t rallying this year the way they did back in 1992. International climate talks have bogged down. In a world where massive corporations dwarf many nations, the U.N. doesn’t have the gravity it once did. And unlike in 1992, which spawned major agreements on climate, biodiversity, and other issues near and dear to greenies’ hearts, the focus in Rio will be on spreading the green economy and making good on past promises.

Nonetheless, their silence is notable. These are the groups that know how to call out the cavalry — or the Horsemen of the Fucking Apocalypse if necessary — when the need arises. So far, I’m not hearing any thundering hooves, and neither, I promise, is President Obama. When I last checked, this petition asking him to attend the Earth Summit had garnered a pathetic 321 signatures.

The Earth Summit, for all its flaws, is a huge opportunity for greens. With climate change pushed to the side, discussions will be focused on spreading renewable energy and creating sustainable cities and food systems — the issues that are energizing a new generation of activists. World leaders will be in attendance — presidents and prime ministers, plus mayors of major cities bigwigs from the business world. Young people will be there in force. One would think that the old guard of American Green might at least pretend to be interested.

Find more of Grist’s coverage of the Earth Summit here.