
Nature as a term can be inclusive and exclusive. It may include everything in existence or exclude products of human agency (e.g. cities, corn fields, art, technology, pollution) from the rest of the world (e.g. old-growth forest, boulders, elephants, fire, snowfall).

The city is often considered separate from the natural world. As a remedy, some call for the integration of nature (usually trees) into urban settings. While I consider this a good thing, the terms imply that cities are not already part of nature. When people use these terms, they don't necessarily intend to be exclusive. It just reflects a deeply ingrained idea of nature without a clear alternative. According to inclusive views, cities are no less natural than birds' nests. Both are constructed by animals with material derived from the Earth. This is not a justification for environmental abuse, but simply an understanding of human activity as within the scope of nature.

Perhaps it is enough to refer to streams, flowers, jets, and sculptures individually, reserving nature to describe the whole. All of the examples above are human concepts, and all are composed of material from the (natural) world. If this view of nature is too inclusive to be useful, is there a simple way to distinguish beehives from buildings, ponds from swimming pools, sunsets from street lights ... ?
(Photo of Portland from Adrian's Photo Blog; Photo of Dolly from Next Nature; Photo of Earth from Wikimedia Commons)