More trees are supposedly needed for carbon sequestration, but if you have too many older trees you get nutrient pollution. From Discovery, Excess Trees in Japan are Harming the Environment
Can trees cause pollution?
Short answer: yes — mismanaged forests can cause nutrient pollution. Cypress and cedar trees in Japan are causing massive amounts of nitrogen runoff into local streams, resulting in harmful algae blooms.
But, it’s not exactly their fault. The trees are planted in massive, commercial plantations, many of which have mostly fallen into a state of disrepair since their establishment half a century ago, during a period of high demand for wood within Japan. For a variety of reasons, Japanese companies began to increasingly import wood in subsequent decades. The shift in the market left in its wake an overabundance of humungous wood plantations, which are now causing major problems for adjacent wildlife in their sad state of ruination.
How many trees do you need to cut? The enviro’s seem to go ballistic when you want to cut trees.