Two words in Mando'a translate to "to preserve." Which one you use depends on the meaning that you're going for.
taylir: to maintain in ideal condition, to prepare for use in the future
(This also means "to hold" or "to keep.")
vencuyanir: to sustain, to keep alive, to prolong, to give support to (a living creature)
(This can be used to talk about helping a living thing or an intangible concept stay alive into the future.)