Great question. One thing I tell my biology students all the time is that people like to make tidy categories and the real world never fits neatly into them. So it’s useful, for example, to talk about theGreater Yellowstone Ecosystem. We can even draw legal boundaries. But that doesn’t mean that elk, fires, rainstorms, or pollen stop at the border.

Back to your question, sure! An ecosystem is all the species in an area, plus all of the non-living things that influence the community, such as water, air, climate, soil, and nutrients. For example, if you want to improve the quality of water off the coast of the city of Santa Barbara, you’d want to study human activities, bacterial communities, wild and domestic animals, water flow starting at the nearby mountains, what the rivers and streams are like, how much of the land is covered with plants vs. concrete/asphalt, rainfall patterns, and many other factors. So it’s useful to think about Santa Barbara as an ecosystem.

Ecosystems are not defined by their size. Your gut is an ecosystem for bacteria. It you’re studying one-celled organisms, a small pond may be an appropriate ecosystem. There will always be things entering and leaving an ecosystem, we just decide on useful boundaries.

Think about where you live. Where does it make sense to draw an imaginary boundary if you want to study it as an ecosystem? It might be very different from something like the official city limit.