In 2015, the Paris Climate Agreement, an accord within the United Nations Framework Convention on Climate Change (UNFCCC) signed by 195 states parties, established a commitment to hold the increase in the global average temperature to well below 2 °C above pre-industrial levels. In order to achieve this objective, the Natural Climate Solutions (NCS), a portfolio of twenty land stewardship options, is one of the main international strategies to increase climate mitigation and an important tool that acts on the three pillars of sustainability: economic viability, environmental protection and social equity.
In particular, the NCS can counter climate change in three main ways:
1 - reducing carbon dioxide (CO2) related to land use and changes in land use;
2 - capturing and temporarily storing additional CO2 from the atmosphere;
3 - improving the resilience of natural ecosystems.
The land stewardship options related to the NCS include conservation, restoration, and improved land management actions that increase carbon storage in forests, grasslands, agricultural lands, and wetlands. Forests can be considered the land stewardship option with the highest climate mitigation potential by 2030. Considering a maximum additional mitigation potential of all land stewardship options estimated at 23.8 PgCO2e y-1, the forest-related NCS can cover approximately two thirds of the total mitigation potential. There are six key forest stewardship options in the NCS: reforestation, avoided forest conversion, natural forest management, improved plantations, avoided fuelwood and fire management. Reforestation is the most common forest-related NCS and requires the active planting of trees and long term care to prevent them from being destroyed or damaged by natural or man-made causes. Avoided forest conversion requires specific nature conservation policies and actions aimed at avoiding the replacement of natural forest with other land uses such as urban areas, croplands, grazing lands and tree plantations. Improving forest management practices such as extending harvest cycles, reduced-impact logging practices and active management of forest stand through cleaning and thinning will allow natural forests to increase their carbon storage while maintaining timber production for the long term. Improved plantations option consists of a lengthening of harvest cycles to increase carbon uptake in timber plantations that are usually managed on shortened harvest rotation lengths. Avoided fuelwood harvest is related to the improvement of cook stoves used in developing countries that burn more efficiently and consequently reduce the amount of wood taken from forests. Finally, fire management is based on fire control practices aimed at reducing forest and savanna fires and the resultant release of carbon into the atmosphere. All the above-mentioned NCS have as their main objective the increase of carbon storage in living biomass—above- and below-ground biomass—and soil. At the same time, the forest related NCS have positive effects not only on carbon storage but also on a range of co-benefits such as conserving freshwater and maintaining species diversity, improving natural hazards protection, water filtration and flood control, increasing aesthetic landscape value and providing recreational opportunities. These co-benefits related to the NCS are commonly defined as “ecosystem services” by the international scientific literature.
According to the Millennium Ecosystem Assessment Report (2005), ecosystem services are the benefits that human populations derive directly or indirectly from ecosystem functions such as raw materials provision, biodiversity conservation, watershed protection and human welfare. From a theoretical point of view the Millennium Ecosystem Assessment has classified ecosystem services into four main categories: provisioning services (e.g., food, energy, water, raw materials), regulating services (e.g., climate regulation, water cycle regulation, natural hazards protection), supporting services (e.g., photosynthesis, biodiversity, soil production) and cultural services (e.g., recreation, aesthetic, cultural and spiritual value). The Economics of Ecosystems and Biodiversity (2010) has replaced supporting services with habitat services, which adds lifecycle maintenance and gene pool protection. Finally, the Common International Classification of Ecosystem Services (2013) reclassified the ecosystem services into three categories to avoid double counts and overlaps: provisioning, regulation and maintenance and cultural ecosystem services. From the practical point of view, the description and classification of ecosystem services is an important starting point for biophysical assessment and socio-economic evaluation of ecosystem services provided by natural ecosystems. Biophysical assessment is the quantitative measurement and characterization of the ecosystem structure and functioning related to the provision of ecosystem services. It helps to understand the functioning of ecosystem and importance of different land uses in the supply of different ecosystem services. Socio-economic evaluation is aimed at estimating the direct benefits to society and thus can support decision-making on land use projects that have impact on different groups of the society. Socioeconomic evaluation provides monetary value to both market goods and services without a market price.
Ecosystem services: important to classify
In the international literature, recent studies highlighted that approximately 30 percent of greenhouse gas (GHG) emissions could be offset by NCS including planting more trees, reforesting degraded forests, engaging in responsible forest management, and improving cropland and peatland management. Those studies estimated that reforestation and avoided forest conversion are the two options with the greatest climate mitigation potential. In addition, it is important to emphasize that these two forest-related NCS are also those with the highest positive impact on a high number of provisioning and regulating ecosystem services (Table 1).
Reforested areas compared to other land uses such as native grasslands, managed pastures, and agricultural lands provide more wood for furniture and biomass for energy use such as timber and bioenergy production, fresh air regulation and carbon storage and protection against natural hazards such as landslides, avalanches, rockfalls and floods. At landscape scale, reforestation may improve relationships among existing remnant forest patches, increasing movement, gene flow and effective population sizes of native species. Reforested areas can also improve the agricultural landscape from an aesthetic point of view thanks to a greater variety of land uses, and create habitats and microhabitats for many species of birds and small mammals, thereby increasing biodiversity. At forest stand scale, reforested areas have the potential to reduce soil erosion and water contamination thanks to roots of trees that are natural nets spreading extensively into the ground to hold the soil in place. In addition, reforestation of agricultural land can improve biodiversity, which can result in increased primary production of chemical energy in organic compounds by living organisms, reduced susceptibility to biological invasion and increased ecological resistance to human pressures.
Conversely, reforestation activities can also have negative impacts on the environment and society related to the choice of tree species and harvest cycles. The use of non-native fast growing species can generate several negative impacts that include competition with multiple-use forestry of local communities, reduction of the level of biodiversity, negative hydrogeological impact in dry areas through soil erosion and run-off, trade-offs in water uses in the irrigation of plantations vs. subsistence agriculture, and increased soil pollution due to the use of herbicides and fertilizers. These negative impacts can be reduced by using native tree species chosen in collaboration with local communities.
Natural forests are best
Generally, natural forests have the capacity to provide more ecosystem services both quantitatively and qualitatively than planted forests and degraded forests. Some natural ecosystems—such as tropical and sub-tropical forests, and wetlands such as mangrove swamps—have a high mitigation potential and at the same time the capacity to provide several ecosystem services for the sustenance of local communities’ livelihoods. In order to increase the biophysical and socio-economic value of ecosystem services provided by planted and degraded forests, improved forest management practices can positively affect the level of species biodiversity, water cycle components, recreational services, forest species composition, horizontal and vertical stand structure and stand density and age. Improved forest management practices, through the extension of harvest cycles, and active forest management, through the cleaning and thinning of planted and degraded forests, can positively influence the following ecosystem services: carbon sequestration in above and below-ground and soil; timber and bioenergy production that increases the quality of wood assortments; mechanical stand stability and the protection of forests against natural hazards; tree and floristic species richness; and recreational opportunities related to the aesthetic values of landscapes. These improved forest management practices have the capacity to increase the biophysical flows of all above-mentioned ecosystem services; however, only a few of them have a real market price, e.g., timber, wood biomass for energy, and climate change mitigation considering the global carbon market. Some scientific studies have estimated that the positive impacts on other ecosystem services not recognized by the market such as biodiversity conservation, landscape quality improvement and natural hazards protection have a potential monetary value greater than 70 percent of the total economic value. Finally, it is important to emphasize that forest-related NCS can provide a key contribution for reducing the greenhouse gas (GHG) emissions in atmosphere in accordance with the need to limit global warming to 2°C. Simultaneously, forest-related NCS can generate important co-benefits for human well-being and quality of life although these benefits are only partially recognized by market prices.
He is researcher at the Italian Council for Agriculture Research and Economics (CREA), Research Centre for Forestry and Wood in Trento. Paletto is editor of five national and international scientific journals (Heliyon, Forests, Annals of Forest Research, Dendronatura and Forest@).