Over the past few months, a handful of major content providers began sensing a more environmentally-attuned zeitgeist building and began offering more eco-centric features. And so, as ClickZ notes, companies have tended to follow the example of Discovery, which earlier this month added eco-friendly lifetsyle site TreeHugger.com earlier this summer. The article points to some similar deals that were struck recently, such as Gaiam.com’s purchase of Lime Media and social net Zaadz, as well as Cleantech’s merger with InsideGreentech.com. But as the piece adds, not all environmentally-centered sites are looking to be bought up. A few are trying to build audiences and attract more advertisers on their own. Publishers such as the Matter Network, which debuted last week and covers environmental-related business news, and SustainLane, a consumer-focused, user-generated directory of green businesses, have begun linking up with ad networks. The two publishers have each sought out Adify to assist them in setting up their own ad networks.

SEE ALSO: Everyone’s Green: WaPo’s Green Site; NatGeo; Hearst’s DailyGreen; Lime’s Green Blog Ad Network

Much like the public’s fickle view toward the environmental movement in general, “green” ad networks have seen spikes in popularity before. About two years ago, GreenAds was started to represent ads on sites such as TreeHugger.com. It took a break last year to shift focus on its integrated marketing firm, SRB Marketing, a more general - and more profitable - property. Adify’s green publishers are betting that the interest in environmental concerns are better able to take hold this year.