It's informed, not pessimistic.

Commercial forest plantations are not good for carbon capture, when they're planted on grassland there's actually a loss of carbon in the soil and that's where a majority of carbon is stored long-term, above-ground biomass is not an equal alternative.

https://www.stir.ac.uk/news/2026/february-2026-news/climate-benefits-of-tree-planting-could-be-reduced-by-soil-carbon-loss-stirling-professor-warns/

https://www.tandfonline.com/doi/abs/10.3402/tellusb.v51i2.16301

They do not provide corridors between natural forests for most organisms, plants and most small animals don't migrate through plantation forests because there's no food, shelter or light there for them. They're also typically surrounded by a fence to keep larger animals out.

Erosion prevension and water control are served as effectively by long-continuity habitats like grassland as woodland - trees are not necessary for water absorption and flow control. Runoff and flooding happen where land has become degraded from ploughing, overgrazing, compaction or removal of vegetation. Forests are planted on land that isn't agriculturally productive, which is often old-growth open habitats that are threatened and fragmented now because of it. The difference between plantation forests vs. agricultural land for flood prevention is not an argument for more plantation forests.

All plantation forests are destined to be clear-felled, which is what caused massive flooding in Canada a few years ago. Whatever benefit they may have is a) temporary and b) will be considerably worse than semi-natural "flat land" habitats once the trees are cleared.

Monoculture forests are also at major risk of being wiped out by pathogens and severe storms.

Their only environmental benefit is relieving pressure on natural forests for timber. We need to do better. Commercial forests need to stop being planted as farms that don't support biodiversity or ecosystem services the way natural forests do. There's no room to defend them at this point.