Background/Question/Methods   Current conservation goals for species diversity are based on island biogeography --- a sound theory here used at an inappropriate scale. Appropriate theory and patterns at the scale of the biogeographical province predict a mass extinction that probably will be twice as devastating as island biogeography’s predictions. To succeed, conservation must learn to deal with anthropogenic habitats.
  Climate change will accelerate mass extinction. Some species now protected will become endangered because the climates of their refuges will be inadequate to support their populations.
  Reconciliation ecology faces these problems by re-engineering anthropogenic human-occupied habitats so that they also support a defined list of wild species.  

Results/Conclusions   We work in metropolitan Tucson, Arizona to start valley-wide efforts at reconciliation ecology. We set up an effective urban breeding-bird census. We determined how we can use aggressive behaviors of hummingbirds to enhance local diversities. We work with schools and neighborhoods to get projects started. And, using the 300-species flora of the world's oldest restoration ecology project, the Tumamoc Hill Ecological Reservation, we designed an n-dimensional method based on minimum-spanning trees to assemble a reasonable candidate set of native species for reconciliation. Trees are pruned to adapt candidate sets to specific slopes, aspects, soils, etc. They can target particular species and build assemblages suitable for deployment in a wide variety of human landscapes. Thus trees allow us to select what we want from a large array of possibilities.
  As reconciliation grows in scope, it will fill in the geographical gaps into which climate change will plunge some species. Not facing such gaps, many species will be able to shift their ranges continuously and avoid at least some of the challenges posed by climate change.
  Although urban and suburban habitats constitute only a small proportion of the land, we must work hard to reconcile them, too, just as we do in our farms and ranchlands. The results will re-integrate people and nature, producing environments that evoke a vacation in a National Park but actually are embedded in our everyday lives. Conservation requires political will and by working in places where most people live, reconciliation ecology can generate that will and become a major player in averting mass extinction.