The carbon costs of global wood harvests

After agriculture, wood harvest is the human activity that has most reduced the storage of carbon in vegetation and soils. Although felled wood releases carbon to the atmosphere in various steps, many carbon-accounting approaches for wood use offset carbon losses from new harvests with sequestration from the growth of broad forest areas, giving the impression of low, zero or even negative emissions from wood harvests. Attributing this sequestration to new harvests is inappropriate because such growth would occur regardless of new harvests and typically results from agricultural abandonment, recovery from previous harvests, and climate change itself. Conversely, approaches that report gross emissions do not account for regrowth. This study presents a new global forest carbon model (CHARM) that applies time discounting to estimate present and future carbon costs of global wood harvests under alternative scenarios. Forest harvests between 2010 and 2050 are estimated to have annualized carbon costs of 3.5–4.2 Gt CO₂e yr⁻¹, approaching common estimates of annual emissions from land-use change due to agricultural expansion. The results imply an underappreciated climate mitigation opportunity by reducing these costs through lower wood harvests or shifts in demand and supply.

Liqing Peng, Timothy D. Searchinger, Jessica Zionts, Richard Waite