From The American Presidency Project, Proclamation 4126—National Arbor Day:

“April of this year [1972] marks the 100th anniversary of Arbor Day, an observance that holds as much significance for the future as it does for the past.

“On a monument erected in Nebraska City to commemorate the founding father of this celebration, J. Sterling Morton, there is this inscription: ‘Other Holidays Repose Upon The Past; Arbor Day Proposes For The Future.’ So it does, for the planting of trees is an action that yields a long-range benefit on generations to come. Arbor Day uniquely symbolizes the truth that the earth belongs to every generation, not just to ours.

“Einstein is believed to have said that a person should put back into this world at least as much as he takes out of it. The best available evidence suggests that an individual American, in his lifetime, uses the wood produced by some 200 mature trees. It is probably too much to expect that each American plant that many trees, but it is not too much to ask that each American assume a large, personal responsibility for renewing and preserving our environmental heritage.”