Marginal nature is found in unmaintained spaces like neglected urban creeks, wastewater treatment ponds, vacant lots, road and rail waysides, industrial wastelands, fencerows, cemeteries, dumps, and alleyways. What emerges in these urban margins is the unintended product of human activity and nature's unflagging expressiveness. Marginality is its defining characteristic both physically and culturally. By traditional natural landscape standards, these margins are usually not aesthetically pleasing, but they can have their own rough beauty that draws nature writers and others to seek encounters with “unofficial countryside” or the “urban wilds” in city margins. However, what they encounter is not wilderness or countryside – but a kind of natural place that strains conceptual categories of nature, because marginal nature in the urban landscape is neither pristine nor pastoral, but rather it is a new kind of cosmopolitan nature whose ecological and cultural value is an open question