Several types of plant species grew in an empty lot. The city counsel decided to turn the lot into a park and planted grass alone to create a playing field. The ecological factor that was MOST LIKELY affected by the change was the lots .

Biodiversity

Explanation:

In the given question, many species of plant species used to grow in the empty lot. The plant species could have provided a home to many animal species. This lot thus formed a small level of the biological ecosystem which is composed of biodiversity.

This lot was changed to a park by the city council which then changed the ecosystem of the area and the main factor that was affected by this change is Biodiversity.

Thus, Biodiversity is correct.