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