The number one mulching material used in landscape is long-leaf pine needle mulch (pine straw). Because pine straw is actually a leaf (needle), it will benefit the environment in the same way that decomposing leaves benefit the forest floor. It will recycle nutrients and maintains soil organic matter in a compost-like fashion.
NO Trees are destroyed in the process of harvesting pine needles so the carbon footprint for harvesting pine needles vs. other mulches is very low. The majority of pine needle harvesting is done by hand, manually using a rake. The pine straw is raked into piles, and then placed into a wooden box for baling.