Green Burials

During yesterday's class we discussed what are called 'Green Burials'. I was really interested in the idea because after being in Europe in 2010 and visiting all of those graves, I wondered how, as time went on, when we were going to run out of space. And from what I understood, the bodies would decompose to feed the earth. ( Here is a link to an interesting e-zine about the concept)
Last night I watched the TEDtalks (Green burial presentation) video that Dr McGuire posted on Moodle and the speaker was talking about these 'hybrid mushrooms' that are used in the decomposition process of Green Burials. And I wondered, have these hybrid mushrooms been introduced in with other mushrooms and what was their effect on the natural wild mushrooms and what is the effect on the natural ecosystem from these fancy mushrooms? The speaker didn't cover these questions, and when this technology comes available to the everyday people, will they damage our world even further rather than hoping to fix the problems that we currently face with current burial techniques?