Now consider a meadow full of flowers, field mice and pigeons, with a hedge along one edge.

Builders cover the whole meadow with a parking lot.

The meadow, with its hedge, before; and the parking lot that covers it after.

The parking lot covers the flowers, and a flower cannot move, so the flowers die.

The parking lot leaves no grass or seeds for the field mice.

But a mouse can run, so the field mice move away to the hedge.

Pigeons pecking at crumbs on the parking lot.

The pigeons eat crumbs dropped on the parking lot, so the pigeons stay and survive well.

The meadow's change: the flowers die, the field mice move away, the pigeons stay and survive well.