Natural Climate Solutions for the United States
Summarized By Michael Higgins
Climate change is real and has been going on now for decades as evidenced from scientific facts and observing the natural consequences all around us. This global problem is complex and hard to grasp, but every person can help by being part of the solution. Some of the these solutions could be, in a general sense, decreasing our environmental ‘footprint’, buying more local products, planting a tree, or even educating ourselves about the effects of climate change and the potential anthropogenic sources of greenhouse emissions. What is also needed for this critical development is leadership and an economy to enable and drive the solutions needed down a sustainable path. The leadership of nearly 200 countries from all over the world have adapted this philosophy as part of an agreement to combat against climate change with the Paris Climate Agreement in 2015. Currently, the United Nations has been the leader in this effort globally and has adopted the 17 Sustainable Development Goals (SDG’s) of the 2030 Agenda for Sustainable Development that have documented global objectives to guide the actions of the international community though 2030. Many of these SDG’s are directly related to climate change solutions. In the United States, The Nature Conservancy is playing a key role in developing strategies for implementation of natural climate solutions (NCS) that can have a significant effect on increasing carbon storage and avoiding greenhouse gas emissions to limit global warming below the 2°C threshold set by the Paris Climate Agreement.
The Nature Conservancy (TNC) documented and quantified 21 distinct NCS applicable to the U.S. that will provide consistent and inclusive exploration of the mitigation potential of conservation, restoration, and improved land management in forests, grasslands, agriculture, and wetlands. The potential for NCS for year 2025 is estimated to reduce greenhouse gas (GHG) emissions by 26 to 28% from 2005 levels, which can be obtainable from anticipated carbon markets paying around $100 per Mg CO2e (e = equivalent) (Fargione et.al, 2018). This information is referenced from a published research article in Science Advances named Natural Climate Solutions for the United States (Fargione et.al. 2018).
The NCS also have co-benefits, without a price on carbon, that are generated by four categories of ecosystem services: air, biodiversity, water, and soil. Of the 21 NCS available, there are 10 opportunities identified that could account for 90% of the maximum NCS potential (Fargione et.al, 2018). According to the scientific results published Fargione et.al. (2018) article, these 10 vital opportunities, referenced under three general categories under 1) Forest, 2) Agriculture and Grasslands, and 3) Wetlands are summarized below.
Forests
- Reforestation – this has the single largest maximum potential (307 Tg CO2e year-1) with the majority occurring in the northeast (35%) and south central (31%) areas of the U.S.
- Natural Forest Management (private) – is the second largest maximum mitigation potential (267 Tg CO2e year-1) which can be achieved by extending harvest cycles in addition to reduced logging and improved silvopasture practices. These management practices can be implemented at low or no net cost and do not require a change in business-as-usual (BAU).
- Fire Management – is a promising opportunity (18 Tg CO2e year-1) which involves restoring frequent, low-intensity, understory fires to reduce the potential for areas of high-severity wildfires and avoid decreased net ecosystem productions from tree-killing wild-fire. There is more research to be completed, however to understand and quantify the carbon storage benefits.
- Avoided Conversion – protects carbon stored in extant forests (38 Tg CO2e year-1) with more than two-thirds of avoided forest conversion potential in the Southern and Pacific Northwest regions.
Agriculture and Grasslands
- Avoided Conversion – the potential of (107 Tg CO2e year-1) includes the avoidance of grassland to cropland prevents emissions from soils and root biomass. There is a much higher rate of emissions as compared with forest due to a higher rate occurs as a result of 28% loss of soil carbon from the top 1 meter of soil.
- Cover Crops– Carbon sequestration in cropland includes the use of cover crops presents a substantial opportunity for mitigation (103 Tg CO2e year-1) comprising of 88 Mha of the five primary crops in the U.S. Cover crops could be grown in fields when fields normally are bare soil provide additional carbon inputs to soils and used to improve soil health, crop yields, and yield consistency.
- Biochar – Carbon sequestration in cropland by amending soils with biochar, which converts crop residue biomass to charcoal through pyrolysis, is estimated to have a mitigation of 95 Tg CO2e year-1.
- Alley Cropping – Supplementary carbon sequestration in cropland by planting wide rows of trees with companion crop grown in the alleyways between the rows, is estimated to have a mitigation of 82 Tg CO2e year-1.
- Improved Cropland Nutrient Management – this involves primarily avoiding N2O emissions by reducing the application rate of fertilizer, switching from anhydrous ammonia to urea while applying best management practices with improved timing and variable application rates within field. This could have a maximum potential of 22% reduction in nitrogen use, estimated to have a mitigation of 52 Tg CO2e year-1.
Wetlands
- Tidal Wetland Restoration – is the largest wetland NCS potential with approximately 27% of U.S. salt marshes that are disconnected from the ocean and subject to freshwater inundation, which results in a significant increase in CH4 emissions. The mitigation of reconnecting these tidal wetlands can avoid these emissions, estimated at 12 Tg CO2e year-1.
The 11 other NCS opportunities identified, in the article Fargione et.al. (2018), accounts for only 10% of the maximum potential summing 122 Tg CO2e year-1. These include the following from highest to lowest mitigation potential:
- Urban Reforestation
- Improved (Forest) Plantations
- Improved Manure Management
- Windbreaks
- Grazing Optimization
- Grassland Restoration
- Peatland Restoration
- Legumes in Pastures
- Avoided Seagrass Loss
- Seagrass Restoration
- Improved Rice Management
We are just beginning to understand what climate change means with the observable negative effects it has on the environment, nature and society. Together we can implement these solutions to make a significant positive impact for generations.
References
Fargione, J. E., Bassett, S., Boucher, T., Bridgham, S. D., Conant, R. T., Griscom, B. W. …et.al. (2018). Natural climate solutions for the United States. Science Advances, 4(11), eaat1869. https://doi.org/10.1126/sciadv.aat1869