Potential greenhouse gas reductions from Natural Climate Solutions in Oregon, USA

Abstract

Increasing concentrations of greenhouse gases (GHGs) are causing global climate change and decreasing the stability of the climate system. Long-term solutions to climate change will require reduction in GHG emissions as well as the removal of large quantities of GHGs from the atmosphere. Natural climate solutions (NCS), i.e., changes in land management, ecosystem restoration, and avoided conversion of habitats, have substantial potential to meet global and national greenhouse gas (GHG) reduction targets and contribute to the global drawdown of GHGs. However, the relative role of NCS to contribute to GHG reduction at subnational scales is not well known. We examined the potential for 12 NCS activities on natural and working lands in Oregon, USA to reduce GHG emissions in the context of the state's climate mitigation goals. We evaluated three alternative scenarios wherein NCS implementation increased across the applicable private or public land base, depending on the activity, and estimated the annual GHG reduction in carbon dioxide equivalents (CO 2 e) attributable to NCS from 2020 to 2050. We found that NCS within Oregon could contribute annual GHG emission reductions of 2.7 to 8.3 MMT CO 2 e by 2035 and 2.9 to 9.8 MMT CO 2 e by 2050. Changes in forest-based activities including deferred timber harvest, riparian reforestation, and replanting after wildfires contributed most to potential GHG reductions (76 to 94% of the overall annual reductions), followed by changes to agricultural management through no-till, cover crops, and nitrogen management (3 to 15% of overall annual reductions). GHG reduction benefits are relatively high per unit area for avoided conversion of forests (125-400 MT CO 2 e ha-1). However, the existing land use policy in Oregon limits the current geographic extent of active conversion of natural lands and thus, avoided conversions results in modest overall potential GHG reduction benefits (i.e., less than 5% of the overall annual reductions). Tidal wetland restoration, which has high per unit area carbon sequestration benefits (8.8 MT CO 2 e ha-1 yr-1), also has limited possible geographic extent resulting in low potential (< 1%) of state-level GHG reduction contributions. However, cobenefits such as improved habitat and water quality delivered by restoration NCS pathways are substantial. Ultimately, reducing GHG emissions and increasing carbon sequestration to combat climate change will require actions across multiple sectors. We demonstrate that

Nature-based cooling potential: a multi-type green infrastructure evaluation in Toronto, Ontario, Canada

“…These include the creation of green space, the mitigation of the urban heat island effect, cooling the environment, and the removal of air pollutants such as ozone and nitrogen dioxide (Alexandri and Jones 2008;Yang et al 2008;Bowler et al 2010;Baik et al 2012;Gago et al 2013;Berardi et al 2014;Feng and Hewage 2014;Nowak et al 2018;Sicard et al 2018;Gourdji 2018;Anderson and Gough 2020). The application of green infrastructure has proven effective in reducing GHG emissions and reducing ambient carbon dioxide concentrations (Berardi et al 2014;Alexandri and Jones 2008;Li et al, 2010;Marchi et al 2014;Bowler et al 2010;Hall et al 2012;Velasco et al, 2016;Fargione et al 2018;Graves et al 2020;Anderson and Gough 2020). For example, green roofing and green wall technologies reduce air pollutant concentrations resulting in urban cooling (Speak et al 2012;Kessler 2013;Anderson and Gough 2020).…”

Quantifying the effects of multiple land management practices, land cover change, and wildfire on the California landscape carbon budget with an empirical model

“…A study on natural climate solutions in Oregon reports that practices associated with woody biomass generally have the greatest potential for increased sequestration and avoided emissions [ 5 ], which is consistent with CALAND. Forest restoration potential in Oregon (on average about -2.5 to -6 Mg CO 2 eq ha -1 yr -1 ) is on par with CALAND (-2.04 to -5.21 Mg CO 2 eq ha -1 yr -1 ), while deferred harvest has less potential than CALAND’s less intensive forest management.…”

“…Outside of California, but consistent with CALAND, practices associated with woody vegetation generally provide the greatest potential for reducing landscape carbon emissions, followed by avoided conversion of natural lands, and then either agricultural management or wetland restoration depending on the implementation area. In Oregon, regardless of implementation scenario, deferred timber harvest provides the greatest potential benefits, followed by reforestation and riparian restoration, and then agricultural management [ 5 ]. CALAND’s BAU estimates of these practices show a similar pattern ( Fig 8 ).…”

“…While the IPCC scenarios consider interactions and tradeoffs with other land dynamics, their global perspective limits specificity and circumvents regional and local limits to implementing land practices [3]. Studies that address practice-specific GHG benefits sum independent estimates, ignoring interactions and tradeoffs among practices, and rarely address other interactions related to land use and land cover change (LULCC), climate change, wildfire, biodiversity, and food security (e.g., [4][5][6]). While McGlynn and Chitkara [7] also use this type of independent accounting method for land contributions to GHG reductions in the United States, they thoroughly discuss the potential effects of interactions and tradeoffs and consider how unaccounted-for uncertainty decreases robustness of estimates.…”

Framing “nature‐based” solutions to climate change

“…Spearheaded by Griscom et al (2017), NCS are intended to “increase carbon storage and avoid greenhouse gas emissions” via enhanced carbon sinks and other means (Fargione et al, 2018, p. 1). NCS have not been cited directly as adaptation tools, although climate resilience has been listed as one of the expected co‐benefits of their development, along with flood control, increased biodiversity, and soil health (Graves et al, 2020; Griscom et al, 2017; Griscom et al, 2020). Examples of NCS are thus concentrated on those actions that are both considered “natural” and that lead to the greatest mitigation effects—Griscom et al (2017) and Fargione et al (2018) have compiled fairly comprehensive lists of approximately 20 examples of NCS, including reforestation, coastal restoration, biochar, and cropland nutrient management (see Table 3).…”