Natural climate solutions are identified and designed with full consideration of risks from climate extremes, natural disturbances, and socioeconomic events.
Prepared by Zach Zobel and Dave McGlinchey
Summary
Many natural climate solutions will take time to reduce net greenhouse gas emissions, exceptions being reducing deforestation and forest degradation, delaying harvest, and reducing emissions from agricultural soils. If benefits are expected to accrue decades into the future, the solutions must consider that climate and other factors will likely be very different and so the expected benefits may not be as great as predicted by current conditions.
Description and Rationale
The impacts of climate change are already being felt and will only worsen, with direct ramifications on natural systems throughout the United States. These impacts will then affect the ability of those natural systems—forests, grasslands, wetlands, and soils—to store carbon and mitigate climate change.
While developing NCS policies, risks should be considered for several climate change perils: drought, precipitation extremes, flooding, hurricanes, heat stress, invasive species, and wildfire. These hazards were identified as the prevalent risks in the United States out to mid-century—a timeframe that is relevant for both mitigation efforts and near-term policymaking. This information should be understood and internalized by policymakers to avoid implementing or investing in NCS that will not remain viable after 20 or 30 years, though some activities like reducing forest degradation could help guard against future hazards. For example, climate risk modeling could help avoid incentives for reforestation in areas that will become more prone to drought in coming decades.
Changing climate conditions will also shift ecological zones. For example, climate change is projected to alter the distribution of tree species as a result of environmental changes that will affect growth, mortality, reproduction, disturbances, and biotic interactions (Rogers et al. 2016). A region that currently sustains certain tree species could become inhospitable, or overrun by invasive species that outcompete native species, or could become warm enough for migrating pests. These projected changes will affect the net greenhouse gas balance of ecosystems in the future and could result in less net emissions reductions than expected.
A mid-century focus requires the use of global climate models (or Earth system models) and we use a ‘business as usual’ scenario for this purpose—RCP8.5 in the vernacular of climate scientists. This scenario is within 1% of total carbon dioxide emissions from 2005 to 2020—even after accounting for a worst case COVID-19 lockdown—and is the closest match out to mid-century as compared to the World Energy Outlook 2019 forward scenarios from the International Energy Agency (Schwalm et al., 2020).
How the principle may be applied to specific climate risks—drought and wildfire
1. Drought
Since the 1980s, droughts have been the second-most costly weather/climate disaster in the United States, generating an average $9.4 billion loss per event (NCEI NOAA). California and much of the western United States are arid regions, historically prone to drought (Bolinger 2019). The 2012–2016 California drought, driven primarily by record high temperatures and less than normal precipitation, was by some measures the state’s most extreme drought of the past century with the 2014 peak the driest period over the last 1200 years (Griffin & Anchukitis 2014). The drought caused a shocking widespread mortality event of 48.9% of the state’s trees across 102 million acres of forests in 2014–2017 in the central and southern Sierra Nevadas, which may lead to forest type conversion of even a long-term shift to grassland (Fettig et al. 2019).
In the future, drought frequency and severity is expected to worsen as global temperatures increase and precipitation becomes more variable (Cook et al. 2015; Huang et al. 2017). By 2021–2050, the probability of extended severe drought at least doubles to 20% across most of the US. Such widespread drought would affect all ecosystems including those essential to sustain food supplies, and could severely impact efforts to reduce net GHG emissions by enhancing carbon sequestration in forests and soils.
