Grasslands may be more reliable carbon sinks than forests in California

Summary, in English

Although natural terrestrial ecosystems have sequestered ∼25% of anthropogenic CO₂ emissions, the long-term sustainability of this key ecosystem service is under question. Forests have traditionally been viewed as robust carbon (C) sinks; however, extreme heat-waves, drought and wildfire have increased tree mortality, particularly in widespread semi-arid regions, which account for ∼41% of Earth's land surface. Using a set of modeling experiments, we show that California grasslands are a more resilient C sink than forests in response to 21st century changes in climate, with implications for designing climate-smart Cap and Trade offset policies. The resilience of grasslands to rising temperatures, drought and fire, coupled with the preferential banking of C to belowground sinks, helps to preserve sequestered terrestrial C and prevent it from re-entering the atmosphere. In contrast, California forests appear unable to cope with unmitigated global changes in the climate, switching from substantial C sinks to C sources by at least the mid-21st century. These results highlight the inherent risk of relying on forest C offsets in the absence of management interventions to avoid substantial fire-driven C emissions. On the other hand, since grassland environments, including tree-sparse rangelands, appear more capable of maintaining C sinks in 21st century, such ecosystems should be considered as an alternative C offset to climate-vulnerable forests. The further development of climate-smart approaches in California's carbon marketplace could serve as an example to offset programs around the world, particularly those expanding into widespread arid and semi-arid regions.

• Author: Pawlok Dass; Benjamin Z. Houlton; Yingping Wang; David Warlind
• Department/s: Dept of Physical Geography and Ecosystem Science; eSSENCE: The e-Science Collaboration; MERGE: ModElling the Regional and Global Earth system; BECC: Biodiversity and Ecosystem services in a Changing Climate
• Publishing year: 2018
• Language: English
• Publication/Series: Environmental Research Letters
• Volume: 13
• Issue: 7
• Links: http://dx.doi.org/10.1088/1748-9326/aacb39
• Document type: Journal article
• Publisher: IOP Publishing
• Topic: Climate Research; Physical Geography
• Keywords: Cap; Carbon cycle; Climate change; Drought; Forest; Grassland; Trade; Wildfire
• Status: Published
• ISBN/ISSN/Other: ISSN: 1748-9326