The reason that science and business connected to establish Biosphere II was to find ways to manage the interrelation of ecosystems. The entire earth is one giant ecosystem subdivided into tens of thousands of lesser ones. We could extend this to our entire galactic neighborhood. The only problem is that as far as we know, the earth is the only part that currently supports life. However, without at least the input of the energy and gravity from the sun and gravity from the moon, our world could not sustain life to be an ecosystem.
The largest single ecosystem on earth is the oceans. This ecosystem interacts in one way or another with every other ecosystem. Nearly all rainfall on the planet originates from water sucked up by the atmosphere as it passes over the oceans. Without water, pretty much everything alive goes away. The oceans regulate the heat of the planet. They are large storage batteries for warmth. The liquidity of water allows things like the conveyor that runs northward in the Atlantic Ocean carrying the heat of the equator toward the arctic circle. This helps to maintain the temperatures that sustain the ecosystems in the northern temperate zones.
The phytoplankton that live in warmer ocean waters generate a huge percentage of the oxygen that we and all terrestrial life on the planet breathes. The oceans themselves act as huge buffers to absorb the pollution and carbon dioxide from the life on land to keep our planet inhabitable. Along the shorelines of the ocean, birds, people, seals, fish, crabs, and a host of other sea and land dwelling animals interact to provide for the needs of each other. People, birds, and seals go fishing. Ocean dwellers like sharks will eat anything from land that ends up near them. Crabs and other tidal creatures work to get rid of dead remains the litter these areas.
The list of interactions between ecosystems goes on and on. Anything that happens in one ecosystem can potentially affect them all. If an ecosystem is large like an ocean, it's effects can be dramatic. If the ecosystem is small like a farm pond, the effect is less and more localized.