Imagine a green world, floating through space. Surrounded by a spherical forcefield that holds air and water in and keeps damaging radiation out. It can only survive where there is bright enough sunlight to allow the vegetation to survive unless it is equipped with power to keep it warm enough and keep artificial lights working for photosynthesis to happen. But plants have a limited lifespan, then they die and with the right biology break down and turn into compost. So the sphere needs to have enough space to keep growing, and enough resources to maintain a steady environment. Maybe there are large bodies of water to supply the plants.
I could be describing little spacecraft that could travel across space and seed new worlds? Or maybe it’s our planet. In either case, the environment needs protecting so that it can survive and thrive. If we imagine earth to be just a small spacecraft, where an imbalance could end its life, then perhaps we might take more care of it. X