On the heels of San Francisco's Arbor Day festivities, the City has announced its Urban Forest Mapping Project, which digitally pinpoints the location of each tree, maintains tree data in a consistent database, and offers web access to the tree data for maintenance and planting efforts.
This is no small undertaking, and because regular folks like you and I can post photos and stories about our own trees and map them online, it's a great example of how a wiki can help us live not in a collection of gardens, but in a true landscape. Thinking of planting an apple tree and wondering whether there's a pollinator nearby? Check the map. Need to know what that monster down the street is that reseeds itself so prolifically? Check the map.
The map is still in the development stages, but already it encompasses something like 140,000 trees. Check it out yourself: look up your favorite neighborhood or favorite tree... or better still, plant one yourself and add it to the database!