Near the start of the 21st century over half the world’s population became urban dwellers. Various global population projections agree that most of the world’s growth will occur in urban areas in the south. Cities are shaped and in turn shape their hinterlands and the cities they are connected to by culture, trade and migration. Consequently urban areas have become a force that is transforming the earth. Today, humanity has unprecedented domination over the Earth’s biogeochemical cycles, the transformation of land surface, appropriation of the products of photosynthesis, and the movement of biota. Global level analysis makes it clear that these transformations are done to support cities, but potentially undercut their ability to sustain themselves. Therefore understanding the ecology of cities is vital both for understanding global change and the vulnerability of people to global change.

A meeting held in Montreal, July 2004, on Urban Biosustainablity established a framework on which future DIVERSITAS research will be based. The following research questions were thought especially important to pursue:

▪ What are the general patterns of urban ecological systems at different scales? What social-ecological drivers determine these patterns?
▪ What do people want from nature in urban settings? What are the health/productivity/social/economic consequences of having urban habitats that satisfy these desires?
▪ What are the policy instruments that can be used, at different scales, to enhance ecosystem services within urban areas, and to enhance urban contributions to exurban conservation and ecosystem services?
▪ In what ways are the patterns of biodiversity (e.g. richness, turnover, abundance, function) in urban and natural ecosystems similar and different, and how does this influence the design and maintenance of urban ecosystems?