Amphibian populations in many parts of the world have been declining. In general habitat loss is the biggest negative impact on species diversity. Recently infection from a chytrid fungus has been linked to killing amphibians. For more information see
http://www.pbs.org/wnet/nature/episodes/frogs-the-thin-green-line/video-full-episode/4882/

For an example of Conservation efforts in Costa Rica see http://english.ntdtv.com/ntdtv_en/ns_sa/2009-11-12/698566099609.html