Nature-based solutions for enhanced carbon storage are an important factor in mitigating climate change. This blog will define Nature-based solutions and show where they could become a solution in the battle against climate change, using agriculture as an example.
Current unprecedentedly high atmospheric concentrations of carbon dioxide are responsible for the anthropogenic climate change whose impact we already notice. These concentrations can be lowered either by reducing emissions or by taking carbon dioxide out of the atmosphere and storing it in terrestrial, oceanic, or freshwater aquatic ecosystems. In these cases, places like soil will become carbon sinks.
What is a sink?
A sink is defined as a process or an activity that removes greenhouse gas from the atmosphere. The long-term conversion of former grasslands and forestlands to cropland (and grazing lands) has resulted in historic losses of soil carbon worldwide. Soil carbon is the carbon, which is stored in soils by natural processes, e.g., by increasing humus, by soil microorganisms or natural weathering of rocks. There is a major potential for increasing soil carbon through the restoration of degraded soils and the widespread adoption of soil conservation practices. These methods are referred to as Nature-based solutions.
How can we use Nature- based solutions for greenhouse gas removal?
Nature-based solutions are defined as methods, based on natural processes, e.g., afforestation, reforestation, biochar amendments to the soil, soil carbon sequestration, wetland restoration. Not all land-based greenhouse gas removal options are automatically Nature-based solutions. A well-known example of a Nature-based solution would be afforestation which increases soil carbon stored in soil but also in the trees themselves. On the other hand, there are initiatives aiming for technically storing greenhouse gas by direct air capture as carbon underground in old mines or directly in the rocks. This is not a Nature-based solution. Where possible, land- (and ocean-) based options should be implemented in a way that constitutes Nature-based solutions because of their inherent potential for sustainable development (Fig. 1).
Sometimes, Nature-based solutions are combined with technological approaches as is done when bioenergy is used with carbon capture and storage (BECCS). In contrast, there are technological methods, but these are not the focus of this post and will not be discussed in more detail. Figure 2 gives an overview of the different methods.
Nature-based solutions in agriculture
Agriculture is an area where climate change has a large impact already, by that also endangers human food security in the long run. On the other hand, the impact of agriculture on climate change is significant too, e.g., by releasing soil carbon into the air or by changing land use completely. Furthermore, agriculture can play an important role in mitigating climate change. Historically, land-use conversion and soil cultivation have been important sources of greenhouse gases to the atmosphere. It is estimated that they are still responsible for about one-third of total GHG emissions.
However, improved agricultural practices can help mitigate climate change by reducing emissions from agriculture and other sources and by storing carbon in plant biomass and soils. There are several methods, e.g., biochar amendments, improved ploughing or irrigation, that reduce agricultural emissions (Fig. 3) and sequester carbon while helping to improve the livelihoods of farmers by securing their harvest.
The objective of Nature-based solutions is to reverse land degradation and land conversion due to deforestation and inadequate land use/management through the promotion of improved land-use systems (e.g., orchards with grassland Fig. 4) and land management practices that provide win-win effects in terms of economic gains and environmental benefits.
Soil carbon storage potential
The development of agriculture during the past centuries and particularly in the last decades has increased the depletion of substantial soil carbon stocks. Agricultural soils are among the planet’s largest reservoirs of carbon and hold potential for expanded carbon sequestration, thus providing a prospective way of mitigating the increasing atmospheric concentration of CO2. It is estimated that soils can sequester around 20 Pg C in 25 years, more than 10 % of the anthropogenic emissions.
Impact on wider ecosystem services
Increased soil carbon storage provides other crucial benefits for soil, crop and environment quality, prevention of erosion and desertification and for the enhancement of biodiversity. Land degradation does not only reduce crop yields but often depletes the carbon content of the agroecosystems. This can reduce biodiversity in soils, but also in the wider agricultural environment. It is therefore important to identify which synergies can be found around Nature-based solutions for soil carbon sequestration coupled with enhancement of biodiversity and stabilisation of cultural ecosystem services.
Carbon sequestration to reach Paris goals
Carbon sequestration activities in agriculture and forestry, with a focus on afforestation/reforestation or improved agricultural management, are seen as being the most effective and readily measurable means to sequester carbon as biomass both above and below ground. In the post-Paris agreement negotiations, efforts are being made to give due attention to the huge carbon sequestration potentials in rangelands and forests. In order to remove as much greenhouse gas as possible from the atmosphere to keep the temperature increase under 1.5 degrees Celsius, the full set of Nature-based solutions should be widely applied now. The adoption of these methods can be increased by the adequate policy which still needs to be implemented in most countries at this point.
Importance of Nature-based solutions
Nature-based solutions are generally less costly and can be used immediately, compared with more technological approaches (Fig. 2). This makes them easier to use right now, to make a positive impact soon, and on a wider scale, also in developing countries. It must be said that Nature-based solutions can be reversed easily, though. For example, afforestation can be easily changed into deforestation again. Often, this will be based on economic decisions which make adequate policy and public funding an important tool to increase and stabilise the results of Nature-based solutions. The Austrian funding for increasing humus and by that soil carbon content in agricultural soils is a good example of that. Unfortunately, this funding is no longer adequate for the current situation but a long-term funding mechanism for increased storage of soil carbon is under development in Austria and other countries. It would be an additional income for farmers and therefore a useful instrument against climate change.
Nature-based solutions are an important measure to mitigate climate change and should be deployed widely and immediately. As these measures increase positive impacts from natural processes, also considering the wider ecosystem services, it can be said that there is no downside when using them. Nature-based solutions would show an immediate effect of reduced greenhouse gases and increased carbon storage and would be an ideal instrument to reach the Paris Agreement temperature goal.
Emde, D., Hannam, K. D., Mist, I., Nelson, L. M., Jones, M. D. (2021) Soil organic carbon in irrigated agricultural systems: A meta-analysis. Global Change Biology 27, 3898-3910, https://doi.org/10.1111/gcb.15680
Fynn, A.J., Alvarez, P., Brown, J.R., George, M.R., Kustin, C., Laca, E.A., Oldfield, J.T., Schohr, T., Neely, C.L., Wong, C.P. (2009) Soil carbon sequestration in U.S. rangelands:
Environmental Defense Fund, New York, NY, USA
NEP (2017). The Emissions Gap Report 2017. Chapter 7, Smith et al.. United Nations Environment Programme (UNEP), Nairobi, ISBN: 978-92-807-3673-1
Ontl, T. A. & Schulte, L. A. (2012) Soil Carbon Storage. Nature Education Knowledge 3(10):35, https://www.nature.com/scitable/knowledge/library/soil-carbon-storage-84223790/
Schmidt, H.-P., Kammann, C., Hagemann, N., Leifeld, J., Bucheli, T.D., Sánchez Monedero, M. A., Cayuela, M. L. (2021) Biochar in agriculture – A systematic review of 26 global meta-analyses. Global Change Biology – Bioenergy, 13, 1708-1730, https://doi.org/10.1111/gcbb.12889
Seddon, N., Smith, A., Smith, P., Key, I., Chausson, A., Girardin, C., House, J., Srivastava, S., Turner, B. (2021) Getting the message right on nature-based solutions to climate change. Global Change Biology 27, 1518–1546, https://doi.org/10.1111/gcb.15513
Vicente-Vicente, J. L., Fuss, S., Song, Ch., Lee, J., Kim., M., Lee, W.-K., Son, Y. (2019) A Holistic View of Soils in Delivering Ecosystem Services in Forests: A Case Study in South Korea. Forests 10(6), 487, https://doi.org/10.3390/f10060487
Fig. 1: Nature-based solutions shown as basis for a wide-spread sustainable development. (Seddon et al. (2021) Global Change Biology 27, 1518–1546)
Fig. 2: Smith et al. (2017) UNEP The Emissions Gap Report 2017 – Bridging the Gap – Carbon dioxide removal (https://www.unep.org/resources/emissions-gap-report-2017)
All other figures (C) Dagmar Henner