If you approach RMNP from Granby (South-West) you will see a gruesome picture of dead forest, mountains with nothing but brown dead pines. As you go up in elevation the picture improves and fewer and fewer trees are dead.
Pine Beetle infestation is attributed to warm winters in recent years and to the Greenhouse Effect.
This picture was taken in the south part of RMNP where it still looks somewhat green.

[PL] insekt Pine Beetle zabija doszczetnie las w nizszych partiach gor. Lagodne zimy w ostatnich latach spowodowaly ze duza czesc lasow sosnowych jest calkowicie umarla. To zdjecie pokazuje czesciowe zniszczenie, niektore drzewa sa jeszcze zielone.