Better land management is needed to achieve the Paris Agreement goal of holding the increase in the global average temperature to well below 2 °C above the pre-industrial levels.
Pathways to mitigate climate change by increasing carbon sequestration and reducing emissions of carbon and other greenhouse gases can be delivered through conservation, restoration, and improved management practices in forests, agricultural & grasslands, and wetlands. Therefore, land-use based mitigation options can help to translate climate commitments into specific and concrete actions that can be taken by governments, private sector, and stakeholders at the local, regional and global level.
Avoided deforestation, forest restoration, and afforestation in tropical regions can provide the greatest climate benefits because carbon storage and biophysics align to cool the earth. Reforestation has one of the highest climate mitigation potential compared to the other land-use based mitigation options.
However, the climate benefits of carbon storage are often counter effective in boreal and other snow-covered regions, where darker trees trap more heat than snow does, therefore causing biophysical warming. Policies for climate mitigation on land rarely acknowledge biophysical factors, such as reflectivity, evaporation, and surface roughness. Yet such factors can alter temperatures much more than carbon sequestration does, and often in a conflicting way.
Planting forests in northern Europe may accelerate climate warming regionally.
Boreal forests provide a different extreme compared to tropical forests. Rates of carbon storage there are much slower than in the tropics because of colder temperatures, less sunlight, and other factors that limit tree growth. Boreal lands are also covered in snow and ice for extended periods each year.
Replacing snow with a surface that absorbs more sunlight, such as an evergreen spruce or pine canopy, warms the area at spatial scales of hundreds or even thousands of kilometers. As a result, planting forests in northern European countries will help to stabilize global atmospheric CO2, but may accelerate climate warming regionally, hence further speeding the loss of snow and ice cover.
Regional climate change, for example in Finland, can be disastrous for the primary agricultural sector because the increased precipitation and cold growing season have left a big portion of the farmers’ harvests in the fields this year. Global climate change is important, but regional climate change can also have a substantial impact.
Forests cover 86% of the land area in Finland with a growing stock 2.5 billion m3 and annual increment of 110 million m3 per annum. Deforestation is not an issue in Finland, but the focal point is to look into the interchange between sustainable forest management with climate change. Does the increase in forest harvesting in Finland reduce the expansion of boreal forests, and therefore lessen biophysical warming in Finland?
Currently, round wood harvesting in Finland is less than 70 million m3 per annum. Therefore, the rate of harvesting is much lower than the rate of forest growth even if round wood harvesting is increased to 80 million m3 per annum.
Boreal regions can use peatland, agricultural and grasslands management to mitigate climate change.
What will be the combined impact of the increase in forest harvesting due to forest management (change in carbon balance), biophysical warming, and aerosol effect (cooling) of forests in Finland, taking into account that boreal forests are growing much faster than round wood harvesting?
Answers to these questions can provide pathways that are sustainable and beneficial for researchers, policy makers, practitioners, and other stakeholders such as farmers and the forestry industry in the efforts to mitigate climate change in Finland, Europe, and globally.
Large scale afforestation in the tropical and temperate regions has potential to cool the atmosphere. On the other hand, one size does not fit all. Therefore, boreal regions can use other land-use based mitigation options such as peatland, agricultural and grasslands management to mitigate climate change.