Sustainability simply means being able to sustain a balance between our lifestyle and Earth's ecosystems.

Yes, there are all too many definitions for sustainability. A truly neutral definition (or as close as one can get), however, wouldn't be fervently anti-development or looking forward blindly to new technology. It's not the method itself -- as in limiting development or using a new gadget for an individual system -- but how that method is employed. Maybe with our exploding population levels iron-clad restrictions on future development will only disadvantage more individuals later. If you actually delve into the growing array of "green" or "appropriate" technologies, though, you also learn quick that almost each one by itself has a unique and significant down-side. CFL's (or "swivel bulbs") may be equivalent to a 60 watt incandescent using only 13, but they're almost all shipped over from manufacturing plants in China and contain uneasy levels of mercury. Solar panels are the cleanest, most unrefined energy source that could ever exist, but within the microfilm is a solvent closely resembling toxic battery acid. Ethonol may be a much less processed, home-grown alternative to fuel, but being made from corn, the monocrop our society is the most dependent on as it now stands, it slaughters food prices by a very strange inter-disciplinary competition and is a large factor in our beginning international nutrition shortages. I don't think I should even have to explain at this point why both hydrogen and so-called "Clean Coal" are ten times more unbelievably counter-productive than all of those. The best individual methods we have are still LED's, Bio-diesel, and fully-electric vehicles (which are in fact MORE than possible already and the models that were out were full mid-size and could drive just as fast as anything have been unmercifully sabotaged by their own manufacturing companies!). None of these will make that big leap by themselves anyway. Sustainability, therefore, is an on-going large-scale interaction between all methods that takes the future into account with each new step. We limit fully wasteful developments but promote new cooperative types of communities. Measuring out the best angle for solar panels before the roofs are built gives maximum energy conversion with minimum toxic surface area. Some CFL's can be up on high ceilings of businesses where they won't damage human lungs if broken while LED's can be in residences. If the auto companies would let us, we could make all new manufacturing of cars those that are only electric and those of us content to drive old-fashioned used cars can keep them going until they're actually run down, and if possible use bio-diesel to keep McDonald's grease from ending up in the ocean. If ethonol could mix with gasoline, everyone could combine them so there's not too much oil plundered from Middle East soil or corn product diverted to fuel at any time. If you look at the larger picture, sustainability should be a large inter-woven web of all these so that the burden finally falls on the community and not the individuals, which has been the main fault of the environment movement. Sure, you can try to solve something like world hunger with scientific breakthroughs of genetically-modified laboratory crops, as Dan suggested at the beginning of this thread, causing untold amounts of new nutritional diseases later, or you can see the root problem of the system and break open the surplus food warehouses of multinationals (where thanks to corporate farm subsidies are encouraged to just sit there and rot) and preventatively redistribute adequate resources that are already here!