Jack Dykinga / Aerial view of Rio Grande passing through the Boquillas Canyon with the Chisos Mountains and Big Bend National Park in the background, Texas, USA on right of river, Mexico on left of river.

Jenny E. Ross / View of the All-American Canal, which carries Colorado River water from the Imperial Dam to the Imperial Valley. USA / Mexico border in California, December 2006

Roger Powell / Algal bloom and plastic debris covering the surface of the Rio Tejo (River tagas) Spanish / Portuguese border, April 2009

Gary K. Smith / English country garden border, with roses and gladioli, leading to doorway, UK, May

Jim Brandenburg / Black Spruce (Picea mariana) forest, Ontario, Border Country, Canada

Jim Brandenburg / Black Spruce (Picea mariana) forest with moss-covered floor, Ontario, Border Country, Canada