Gardening and urban landscaping: significant players in global change.

Global warming leads to shifts in vegetation types in given temperate environments. The fastest species movement is due to the globalized supply and use of exotic plants in gardening and urban landscaping. These standard practices circumvent dispersal limitations and biological and environmental stresses; they have three major global impacts: (i) the enhancement of biological invasions, (ii) the elevation of volatile organic compound emissions and the resulting increase in photochemical smog formation, and (iii) the enhancement of CO(2) fixation and water use by gardened plants. These global effects, none of which are currently considered in global-change scenarios, are increasingly amplified with further warming and urbanization. We urge for quantitative assessment of the global effects of gardening and urban landscaping.