1. What are natural climate solutions

Natural climate solutions (or NCS) are approaches used to limit global warming by working with natural and managed forests, grasslands and agriculture, as well as wetlands systems to lower concentrations of greenhouse gasses in the atmosphere. This is accomplished by employing land use and management strategies that avoid greenhouse gas emissions and enhance carbon sequestration.

2. What are mitigation pathways?

Pathways are activities that involve specific conservation, restoration, and/or improved land management actions that practitioners may take to avoid emissions and/or enhance sequestration.

State level pathway estimates are aggregations, based on national datasets.

3. What does the term mitigation refer to in this context?

In this context, mitigation refers to the ability of natural and managed terrestrial and wetland systems to contribute to diminishing the global temperature rise by reducing or stopping greenhouse gas emissions or by absorbing carbon from the atmosphere.

4. What does the term mitigation refer to in this context?

In this context, mitigation refers to the ability of natural and managed terrestrial and wetland systems to contribute to diminishing the global temperature rise by reducing or stopping greenhouse gas emissions or by absorbing carbon from the atmosphere.

5. How did you calculate the NCS mitigation potential?

The Unites States NCS analysis is based on research and a synthesis of hundreds of studies conducted over 18 months years involving 38 researchers from 23 organizations.  Combining factors of land conversion rates, stored terrestrial carbon, greenhouse gas emissions, carbon sequestration rates, and extent of habitat or land use in the case of agriculture management, researchers quantified the total amount of carbon and carbon dioxide equivalent (CO2e) that would be absorbed by natural systems if conversion was halted, as well as the amount that would be absorbed from the atmosphere under various restoration and improved management activities for each of the 21 mitigation pathways.

6. What is the Paris Agreement?

The Paris Agreement, drafted at the 2015 Conference of the Parties (COP) of the United Nations Framework Convention on Climate Change (UNFCCC), brought together more than 190 countries to draft an agreement to reduce greenhouse gas emissions and respond to the threat of climate change by keeping the global temperature rise below 2°C this century.

7. What are NDCs?

NDCs, or Nationally Determined Contributions, are pledges countries developed for the 2015 Paris COP describing methods and targets they will undertake after 2020 to reduce greenhouse gas emissions. Efforts outlined in NDCs are meant to keep the global temperature rise below 2°C this century in as stated in the Paris Agreement.

8. What is maximum mitigation potential?

Maximum mitigation potential is the total amount of climate mitigation possible through the implementation of pathway activities from a natural or managed system, considering nature’s full ability to store or absorb carbon based on its total global extent. Under this scenario, implementation of pathway activities is not limited by cost, but it is constrained by maintaining land area to meet society’s requirements for food and fiber by no reduction in cropland.

9. What are marginal abatement costs in reference to mitigation potential?

For each NCS opportunity, we constructed the marginal abatement cost (MAC) curve from the available information in the literature. A marginal abatement cost curve represents the monetary cost of achieving one additional ton of sequestered greenhouse gases (GHG) or avoided GHG emissions and indicates the total quantity of net GHG reductions that can be achieved at different price points. We estimated the total abatement available at USD 10, 50, and 100 Mg CO2e-1.

Scientists project that climate change will cost society more than $100 per ton of CO2 emitted if we do nothing. Therefore, spending up to $100 per ton should be considered cost-effective. This proportion of the maximum potential mitigation total is the best measure for understanding society’s ability to employ natural climate solutions as a response to climate change.

10. Why are there only eleven pathways shown in the US State Mapper?

The scientific analysis underlying the mitigation data presented in the study considered 21 pathways, however due to data limitations, only 11 climate mitigation pathways area available to view at the state level.  The data for the pathways not included in the US Mapper (Natural Forest Management, Improved Plantations, Biochar, Windbreaks, Grazing Optimization, Legumes in Pastures, Tidal Wetland Restoration. Peatland Restoration, Avoided Seagrass Loss, and Seagrass Restoration) are either not spatially explicit or only exist at a country scale and cannot be disaggregated to the state level.  For example, there are significant opportunities for NCS in natural forest management and wetland pathways that are not presented in the Mapper due to inadequate state level data. The 11 spatially explicit pathways presented in the State Mapper are significant in terms of their climate mitigation potential representing 60% of the Unites State’s NCS potential.

11. What are the limitations of the data presented in the State Mapper and how should I use the information presented to understand the mitigation potential from land use in relation to our national or state level emissions?

The aim of the State Mapper is to serve as an initial engagement tool to make build awareness of the potential Natural Climate Solutions at the national and state level; to serve as a starting point for deeper dives to more accurately assess their real NCS related activities potential to reduce emissions and help mitigation climate change.

The state level pathway estimates presented in the US State Mapper are aggregations based on country level datasets and in most cases do not use official state datasets and/or baseline setting procedures.

12. Where can I find information on the science behind the US State Mapper?

Link to Science Innovations Paper

 

13. Pathway definitions

Reforestation – Additional carbon sequestration in above and belowground biomass and soils gained by converting non-forest (<25% tree cover) to forest [>25% tree cover ] in areas of the conterminous U.S. where forests are the native cover type. To safeguard food production, we removed most cropland and pasture. We reduced the carbon sequestration mitigation benefit in conifer-dominated forests to account for albedo effects.

Fire management – Use of prescribed fire to reduce the risk of high-intensity wildfire. We considered fire-prone forests in the western U.S. We assume that treatment eliminates the risk of sequent wildfire for 20 years, but only on the land that was directly treated. We report the average annual benefit across these 20 years. The impact of wildfires includes both direct emissions from combustion and suppression of net ecosystem productivity following wildfires.

Avoided forest conversion– Emissions of CO2 avoided by avoiding anthropogenic forest conversion. To estimate the rate of conversion (i.e. to another land use), we first calculate forest clearing in the conterminous U.S. from 2000 to 2010 and estimates of avoided carbon emissions from above and below ground biomass that are specific to each region and forest type. We did not count forest loss due to fire or pests. We reduced the benefit of avoided conversion in conifer-dominated forests to account for their albedo effects.

Urban reforestation – Carbon sequestration in aboveground and belowground biomass gained by increasing urban tree cover in 3,535 cities in the conterminous U.S. We considered the potential for additional street trees and, for those cities not in deserts, we also considered the potential for park and yard tree plantings. We excluded sports fields, golf courses, and lawns.

Cover crops  – Soil carbon sequestration gained by growing a cover crop in the fallow season between main crops. We quantified the benefit of using cover crops on the five major crops in the U.S. (corn, soy, wheat, rice, and cotton) that are not already growing cover crops.

Avoided conversion of grassland – Emissions of CO2 avoided by avoiding conversion of grassland and shrubland to cropland based on conversion rates from 2008-2012.

Alley cropping – Carbon sequestration gained by planting wide rows of trees with a companion crop grown in the alleyways between the rows.

Cropland nutrient management – Avoided N2O emissions due to more efficient use of nitrogen fertilizers and avoided upstream emissions from fertilizer manufacture. We considered four improved management practices: 1) reduced whole-field application rate, 2) switching from anhydrous ammonia to urea, 3) improved timing of fertilizer application, and 4) variable application rate within field.

Improved manure management  – Avoided CH4 emissions from dairy and hog manure. We estimated the potential for emissions reductions from improved manure management on dairy farms with over 300 cows and hog farms with over 825 hogs.

Grassland restoration – Carbon sequestration in soils and root biomass gained by restoring 2.1 Mha of cropland to grassland, equivalent to returning to the 2007 peak in Conservation Reserve Program (CRP) enrollment. Grassland restoration does not include restoration of shrubland.

Improved rice management – Avoided emissions of CH4 and N2O through improved practices in flooded rice cultivation. Practices including mid-season drainage, alternate wetting and drying, and residue removal can reduce these emissions.

 

 

 

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