Researchers: Unmanaged forests now emit more CO2 than they absorb

Forest in Estonia.
Forest in Estonia. Source: Laura Raudnagel

Much forest area has been lost as a result of urban sprawl, the construction of roads and railroads, the restoration of meadows and bogs and other environmental conservation efforts. The only proper course of action would be to establish the same volume of forest elsewhere. In addition, failure to properly manage the remaining forest reduces the capacity of our forests to sequester carbon dioxide (CO2), write researchers from the Estonian University of Life Sciences (EMU) in a joint commentary.

As a scientist, it is extremely difficult to propose magic bullet solutions to our climate change goals, yet policymakers in the European Union tend to do so with regard to LULUCF (land use, land use change, and forestry) sector greenhouse gas reduction targets.

Is LULUCF really a panacea that will help the most in meeting our "Fit For 55" climate targets?

To put it simply, one of the pillars of achieving current climate goals is that the LULUCF sector must sequester the same amount of carbon that it emits. This applies to all land uses, including forest land, farmland, grassland, wetlands (including peat bogs), settlements and other types of land. Everything, above- and below-ground live biomass, dead organic matter and soil carbon is counted.

However, the goal is not to attain carbon neutrality or zero emissions, but rather to raise CO2 sequestration to 310 million ton by the end of the decade.

While this is an ambitious goal in and of itself, the broader problem still is that the volume of both agricultural and forest land is decreasing for a variety of reasons.

The greater the area of land removed from these two land-use categories, whether for urban sprawl or road and railroad development with the associated removal of agricultural and forest land, the greater the burden of carbon sequestration on forest land in particular.

Forest land that has been already lost due to the construction of a four-lane highway or Rail Baltic cannot be recovered. The only other option would be to plant the same amount of forest in a different location.

Also, the fact that forest area has already been lost due to the restoration of meadows and bogs or through nature conservation efforts, in addition to the logging mentioned above, is also rarely addressed.

Nature reserves (30.3 percent of total forest area, of which 17.5 percent is strictly protected and 12.8 percent is subject to economic constraints) cannot be relied upon to meet our climate targets and sequester carbon for an extended period of time. These ecosystems support biodiversity -- they do not effectively sequester carbon.

Because the carbon sequestration capacity of a forest stand decreases with age, carbon-neutral ecosystems are found in older forests, where CO2 emissions and sequestration are in balance.

However, when older forests no longer absorb as much carbon and due to disturbances or extreme weather, they can themselves become a source of carbon dioxide.

Young and middle-aged forests, on average, sequester more carbon from the atmosphere than older forests. To achieve our climate goals, we must acknowledge that removing forest land from management, in whole or in part, for any reason, reduces the capacity of our forests to sequester carbon dioxide (CO2), because as forests age, their growth factor decreases, and with it, decreases their carbon sequestration effectiveness.

Forests will continue to combat climate change so long as their biomass volume increases. As forests age their vitality and disease resistance decline and they also become more vulnerable to a variety of stressors such as fire, storms, drought, floods, fungal diseases and insect damage (e.g. worms).

Increasing the percentage of old and overgrown commercial forests relative to total forest area is not a viable strategy for meeting long-term climate targets.

Also, the amount of carbon absorbed by the wood industry is declining, which has negative economic effects as well (e.g. loss of added value, loss of share of higher-value varieties, loss of land owner-occupation and investment in forestry).

Agricultural land use poses even greater challenges, e.g. peat soils (22 percent of total land and 8 percent of arable land) emit carbon when they are cultivated and their continued use in conventional agriculture will increase greenhouse gas emissions. However, it should be noted that in a longer-used peat soils this degradation is already ending and emissions are decreasing.

Why are such soils used for agriculture? Foresting these areas and allowing them to store carbon dioxide through timber production would be the most reasonable course of action.

However, caution must be exercised; this should not be motivated by a desire to stop draining these areas, which would be devastating because forests cannot grow in a silt environment; they perish.

To sum up, we are all concerned with leaving the smallest possible footprint on the environment and we do everything we can to limit emissions. So we should not overlook the natural ability of our environment to absorb CO2.

If we expect the LULUCF sector to sequester carbon at least at the same rate as it emits, we should avoid removing forest land from use and continue manage it, so that the forest, as a natural buffer, retains the capacity to do absorb more carbon than it emits.

Marek Metslaid is the director of the Institute of Forestry and Engineering; Ahto Kangur is the head of the chair of Forest and Land Management and Forest Industries; Endla Reintam is the vice rector of studies; and Allan Sims is a senior research fellow at the Estonian University of Life Sciences.


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Editor: Kristina Kersa

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