Humans have disrupted certain critical environmental cycles (water, carbon, nitrogen, and more) so fundamentally that continued damage to health, habitat, and economies is inevitable. Fortunately, a lot of creativity is being applied to reducing or eliminating human impacts, such as the No Impact Man project (my article on this will be forthcoming this week on Wiley GeoDiscoveries and I will update the URL when it is).
As Colin Beavan himself has pointed out, some impacts are unavoidable, so having no net impact means that some restorative measures should also be undertaken -- planting trees, restoring wetlands, replenishing eroded beaches, picking up trash, and so on.
building coated with titanium dioxide and special solar panels, enabling it to neutralize smog-forming chemicals on a 24-hour basis.
With current technologies, the production of concrete is a major source of climate-changing carbon dioxide. Concrete and Carbon is a Science Friday segment that explains why this is and -- more importantly -- describes the possibility that concrete formulation could be altered in a way that would allow it to sequester carbon, allowing each building, roadway, or sidewalk to have a positive net impact on the global environment.
My friend Wing-kai let me know about another emerging technology that seems almost a hybrid of these two: using titanium dioxide in concrete to offset local pollution. As some of the online comments have suggested, even the most promising of these technologies are potentially fraught with trade-offs or limitations, and they do not provide any excuse to back off on the most important environmental strategy of all: conservation!