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Listen to part of a lecture in an environmental science class. Professor: Today we're going to discuss a fascinating example of how human activity can inadvertently create new ecosystems. I'm talking about the 'green roofs' of cities, but not the intentional ones on modern buildings. Instead, consider the abandoned industrial sites, like old railroad yards or factories, that have been left to nature for decades. On these sites, a unique type of vegetation has developed, often including species that are rare or even endangered in their original habitats. For instance, in the UK, certain lichens and mosses that were once common on heathlands now thrive on the gravel and concrete of derelict urban lots. These 'accidental habitats' support a surprising diversity of insects and birds. The key point is that these ecosystems are not just degraded remnants; they have evolved their own ecological dynamics. While conservationists often focus on preserving pristine wilderness, some scientists argue that we should also value these novel urban ecosystems. They provide ecosystem services, like cooling the air and absorbing rainwater, and they offer a connection to nature for city dwellers. However, there is a debate: should we manage these sites to preserve their accidental biodiversity, or should we restore them to a more 'natural' state?