From sink to source: Regional variation in U.S. forest carbon futures.

David N Wear,John W Coulston

doi:10.1038/srep16518

Abstract

The sequestration of atmospheric carbon (C) in forests has partially offset C emissions in the United States (US) and might reduce overall costs of achieving emission targets, especially while transportation and energy sectors are transitioning to lower-carbon technologies. Using detailed forest inventory data for the conterminous US, we estimate forests’ current net sequestration of atmospheric C to be 173 Tg yr−1, offsetting 9.7% of C emissions from transportation and energy sources. Accounting for multiple driving variables, we project a gradual decline in the forest C emission sink over the next 25 years (to 112 Tg yr−1) with regional differences. Sequestration in eastern regions declines gradually while sequestration in the Rocky Mountain region declines rapidly and could become a source of atmospheric C due to disturbances such as fire and insect epidemics. C sequestration in the Pacific Coast region stabilizes as forests harvested in previous decades regrow. Scenarios simulating climate-induced productivity enhancement and afforestation policies increase sequestration rates, but would not fully offset declines from aging and forest disturbances. Separating C transfers associated with land use changes from sequestration clarifies forests’ role in reducing net emissions and demonstrates that retention of forest land is crucial for protecting or enhancing sink strength.

Highlights

Growth by 0–2% annually[13,14,15]
Using State level data, we decompose these changes into C transferred with land use changes and net C sequestered from the atmosphere by forests
While forest C sequestration grew in the East between 1990 and 2013, it declined in the West—most of the increase in forest C accumulation between 2000 and 2010 results from forest area expansion in the East (Fig. 1D)

Summary

Introduction

Growth by 0–2% annually[13,14,15]. Other climate change impacts including change in growing season length, water availability, and temperature interact with atmospheric changes to determine growth responses[16,17]. Forest growth rates peak and slow as forests mature[9] so forest aging is a significant driver of sequestration. Natural disturbances (e.g. fire, weather, insects and diseases) and human-mediated disturbances (e.g. forest cutting) can result in C emissions, alter accumulation rates, and modify the forest age structure[18,19,20,21]. Productivity shifts due to climate change, and a policy alternative are addressed using scenarios.

Methods

Results

Conclusion