| "climate change" | "environmental protection" | "green movement" |
| "global warming" | "environmental justice" | "renewable energy" |
| "carbon footprint" | "social responsibility" | "alternative energy" |
| "non-governmental organization" | "greenhouse gasses" | sustainability |
| pollution | ecology | "sustainable development" |
| emissions | agriculture | "energy policy" |
| "waste management" | "political ecology" | nature |
| biodegradability | ecotourism | wildlife |
| compost* | recycl* | sea level |
| agriculture | "going green" | "environmental engineering" |
| wildfires | drought | mitigation |
| fossil fuels | "effect of human beings" | glaciers OR "glacier retreat" |