Why are crop fields known as artificial ecosystem?

A crop field is an artificial ecosystem as it is made by man.  In the crop fields, the biotic and abiotic factors are regulated based on the requirement for crops. In crop fields, plants such as rice, wheat, vegetables, etc. are cultivated. Farmers establish the relationship between abiotic factors and producers.

[Extra information:

Two natural ecosystems are Grassland and forest.

Two artificial ecosystems are Parks and Gardens.]