Yeah I actually disagree with you Bathilde, I feel the Earth is sacred, there are sacred places: land untouched by humans and burial grounds of any race or culture. If you find the your homeland beautiful (as I do, I love where I live), you will respect it. This respect could grow to such a degree that you consider the Earth, the cradle of human life, to be sacred.
Remember that Earth (Jörð) is a is a female jötunn (or goddess, since she is coupled with Odin), Thor's mother and the personification of the Earth. So, Odin created the Earth with his brothers and Odin created Thor with himself and the Earth. Midgard is a very importance part of Heathenism, without a doubt. So Bathilde, there is a spirit of the Earth, a goddess, that is the Earth, and she is both a goddess and Midgard. It's a small and overlooked part of Norse cosmology.
As for environmentalism, I recycle and plant trees on my already well forested land. We also compost waste food and grow a small half acre garden. I cannot really cut back on emissions from my vehicle except by walking and bicycling, which is really hard in a rural area. I'd like to be as green as possible. Imagine a 'green' off the grid Hof! All it would need is a phone line! A well, and some solar panels would be all you would need the only reason we don't have impressive extravagant Hof is because of the fact that we're spread too thin. You could build it not totally underground, but have the walls turfed in, like the structures at L'Anse Meadows. Dream big!!!
P.S. (There could be a Heathen 'colony' in Walhalla, SC)