Trees and Causality

By Marian Moszoro

In the restrooms at a government school of a leading university the following announcement was posted:

“We are happy to announce that CGIS will now feature:

* 100% recycled paper products

[...] The benefits of these changes include:

* 17 trees saved per ton of recycled paper”

While I am not an engineer and cannot assess how many trees are needed for the production of one ton of paper, I am quite sure that the large share of trees used in the production of cellulose worldwide comes from forests that were planted for the sole purpose of paper production.

In comparative statics, the causality claim of saving trees by using recycled paper is true. But when adding dynamics, causality becomes less obvious...

Assuming away energy loss, the poster could arguably have read: “Due to our changes, 17 trees will not be planted per ton of recycled paper.”