This week saw the launch of a second round of location-based social media linked advertising for the San Franciscan non-profit environmental law firm, Earthjustice. Following on from their highly successful May campaign that called on BART commuters to “Use your cell phone to drill the oil industry”, the law firm has now launched a campaign to raise money to help save the endangered Pika.

At the start of the summer Earthjustice blanketed San Francisco BART stations with posters that called on commuters to checkin at their ad on Foursquare to help the firm to stop “unsafe oil drilling”. The campaign followed the tragic BP oil spill disaster and promised to donate $10 to the cause from a company donor for every checkin that was made.

The campaign was specifically targeted at younger audiences who don’t typically respond to advertisements of a charitable nature. The aim was to combine a heartfelt and compelling message with a modern technological trend to inspire this younger demographic to take interest in environmental causes.

The latest campaign, launched on Monday, again calls for commuters to use their smartphones to check in to their ads on Foursquare but this time the good cause is the Pika, which has become an endangered species due to climate change. The ads read: “What does it take to help save the endangered pika? About 20 seconds”. Again, for every checkin, an Earthjustice donor will donate $10 to protect the Pika.

Not only does the Earthjustice campaign demonstrate a hugely successful engagement with the public, generating over 5,700 checkins and associated extended social messaging (‘Likes’, shares, Tweets etc.), but more importantly the law firm are among the first businesses to drive people to checkin at a physical billboard as a method of engagement and interaction.

The New York Times references industry analysts and Foursquare executives as saying that the tactic has proved very successful and is sure to attract other advertisers.

“Tying in location allows the advertiser to see which particular ads are more successful at prompting responses,” said Noah Elkin, a mobile marketing analyst at eMarketer, a New York research firm. “Plus, checking in allows each person to share what they think is important about the ad campaign. If they post their check-ins to Facebook and Twitter, you’ve reached a much broader audience.”

While it seems that the whole idea originally sprang out of an offer of free ad space to run public service announcements at several Bay Area Rapid Transit stations, the mechanic stands alone and demonstrates real innovation. Considering that the environment that the ads are in inherently creates a situation of thousands of people a day standing in front of and staring at ads, Earthjustice have developed a low barrier, immediate response, feel good campaign that simple put, is a no brainer.

“A lot of the time people are standing around BART checking their phones as they wait for their train, so it was a no-brainer to use Foursquare as way to get them to engage with the ads and support our work” said Ray Wan, the marketing manager for Earthjustice, which is based in Oakland, Calif.

Of course a huge part of the appeal of Foursquare is gaining and holding “mayorships”. The user who has checked in to a location the most often, most recently is awarded the title of “mayor”. People can become quite fanatical about their “mayorships”, especially commuters who visit or pass the same location every day. The knock on effect of this is that the platform itself then drives more donations as users compete to become the mayor.

In fact, this innovative concept is now being looked at by other businesses, both charity and non-charity, to create similar check-in campaigns according to Tristan Walker, Foursquare’s head of business development.