He-She is just telling that there is a difference between a garden and an actual wild nature space. Gardens are manicured environments with a fraction of biodiversity that are made to serve human needs, and also frequently require constant maintenance and resource consumption on garden tools, fertilizers, etc, and frequently are changed whenever the house changes owner or tenant. They do not contribute to nature preservation at all actually, they just provide more comfort to the inhabitants like some trees for shading. A real wild nature space demands a lot of continuous space devoid or almost devoid of human presence or interference, like a whole Manhattan island of trees that will not be cut, and no fertilizer maintenance at all, and big animals that are dangerous to humans such as wolves, bears, moose, etc.