Abstract

  • counting newly grown wood from harvested forests as extra is wrong because this growth would also happen without harvesting
  • harvesting forests leads until 2050 to additional eCO$_2$ in the realms of land use change due to agricultural expansion

Main text

  • depending on how you count, harvesting wood might not be just C neutral but even benefit the climate
  • reporting at national level allows countries to look C neutral
  • harvesting should decrease this benefit, but is not reported separately
  • net increase in forest C makes countries appear to have no emissions
  • reporting net effects of new wood harvests and regrowth from previous harvests leads to similar effects (no identification of effects of new wood harvests alone)
  • appears that harvesting in temperate countries is beneficial and in tropical countries it is costly (in terms of climate)
  • wrong accounting: Growth that would occur anyway cannot offset harvesting costs.
  • so far: mostly spatial offsetting, or offsetting with past growth
  • possible: offsetting with what grows in the same place after the harvest
  • harvests lead to short-term emissions and undermine Paris Agreement

Accounting for time in estimation of GHG costs

  • CHARM (carbon harvest model): new global forest C model
    • live vegetation, roots, slash, different wood products and landfills
  • computes annual difference in scenarios: forest would have grown, forest is harvested
  • emissions discounted with 4% per year: the earlier the heavier
  • SCC (social carbon costs): for instance cost for mitigation might decreaste with better technology
  • mitigation now is more valuable (costly), already included in the discount
  • discount can be seen as interest rate for companies on today’s emissions, they will have to pay back more later

Growing wood demand

  • long-lived wood products (LLP): sawn wood, wood panels, and other industrial roundwood
  • short-lived wood products (SLP): paper and papaerboard products
  • very-short-lived products-wood fuel (VSLP-WFL): wood harvedted deliberately for energy
  • very-short-lived products-industrial (VSLP-IND): waste from manufacture of other wood products, burned for energy
  • wood harvests will increase by 54% globally between 2010 nd 2050, mostly SLP; VSLP-WFL most uncertain
  • substituton effects for steal and concrete
  • “clear-cut-equivalents”: area necessary by clearcutting to get the same amount of wood
  • nice flow-chart of wood products

Robustness of results

  • 3-5 GtCO$_2$e per year
  • probably conservative: effects of harvests on soil C not counted: meta-analyses show quite some soil C loss
  • indirect effects such as road building ignored (can be several times direct effects)

Insensivity to discount rate

  • robust if society has a small preference for short-term over long-term mitigation

Meaning of economic effects

  • Compare harvesting with no human activity instead of another human activity such as land use change, otherwise you are covolving numbers.

A potential mitigation option

  • harvesting comes with carbon costs, offsetting is usually done in wrong ways
  • comparing them with land-use change due to agricultural expansion makes costs disappear, because costs are about equal
  • No harvesting mitigates climate change.
  • Later, mature forests might sink in C slower, but no harvesting now would buy us time.