Gardner’s definition:

Naturalist intelligence designates the human ability to discriminate among living things (plants, animals) as well as sensitivity to other features of the natural world (clouds, rock configurations).  This ability was clearly of value in our evolutionary past as hunters, gatherers, and farmers; it continues to be central in such roles as botanist or chef.  I also speculate that much of our consumer society exploits the natural intelligences, which can be mobilized in the discrimination among cars, sneakers, kinds of makeup, and the like.  The kind of pattern recognition valued in certain sciences may also draw upon the naturalist intelligence.