As you have found out ecosystems include both living and non-living things. The living things in an ecosystem are referred to as the biotic factors. The nonliving things are the abiotic factors.
When one factor (biotic or abiotic) is changed in an ecosystem it can affect many other things. Biodiversity (the variety of living things in an ecosystem) is usually one of the first things affected by any changes.
Biodiversity increases with an increase in biotic factors.